eHam

eHam Forums => Amplifiers => Topic started by: KB1SNJ on January 13, 2017, 10:10:32 PM



Title: Which amp to start with?
Post by: KB1SNJ on January 13, 2017, 10:10:32 PM
I know general question but I've seen numerous options in the classifieds, just looking for ideas and experiences.

I have a very tight lot, with a 50ft vertical above a 9:1 unun running 100watts. I really do not have much antenna options, no space for a ground plane array either.

A lot of stations that I can hear, cant hear me. So I think an amplifier may help compensate for the antenna deficiency.

Thinking that 1000 watts would be good. I have had issues with RF in the house tripping GFCI, etc but when I went to the vertical it seems to have gotten better (although my computer monitor still goes wonky with 100 watts)

Anyway, I'd need a robust amplifier because I am going to make mistakes operating initially. Budget is also a big issue.

ideas? experiences?






Title: RE: Which amp to start with?
Post by: KK4YDR on January 13, 2017, 11:08:39 PM
Well I am sure you know this already. But an amplifier can only improve upon a poor antenna poorly. But a good antenna an amplifier can make it much better.

However, in the meantime from the sound of it and your limited options, if you have indeed exhausted all antenna options, an amplifier can boost your signal. I HIGHLY recommend seriously looking into your antenna situation before making a jump to an amplifier. My personal experience and many others will tell you that the amplifier is the L A S T item to place in the shack when all other elements have been perfect as much as you can. The antenna is 95% of the performance on the air and the other 5% is the amplifier realistically. I have heard stations running 1000 watts with absolutely poor signals that were hard to hear and found out that their antenna was pure compromise or junk overall. On stations with a great antenna you can hear them quite well without an amplifier then you will hear them exceptionally well with an amplifier.

With that being said - I recommend a few amps based on price range and want/need/performance in reality.

With amplification on HAM radio the first 500 watts absolutely makes the biggest difference, The next and rather large increase is going to 1 kw. Going to 1500 watts is really a waste of money except in the most extreme cases where it matters. Oh and it does make you louder without really increasing signal more than a KW.

If you are on a tight budget, and are willing to accept, or are comfortable with a beginner amplifier - Ameritron AL-811. The tubes are cheap as dirt and if you blow one just change it like a 20 dollar lightbulb.

If you have more money but don't want tubes, get the Ameritron ALS-600 solid state. Good for around 500-600 watts output.

If you want to spend more money, around the same as the ALS-600, I HIGHLY recommend the AL-80B. Single 3-500Z amplifier and is good for a realistic 700-850 watts. More and you are pushing the amp and tube hard.'

Where you say "Anyway, I'd need a robust amplifier because I am going to make mistakes operating initially. Budget is also a big issue."

This is where I recommend the AL-811 to learn on. It is robust in the sense that it is going to be hard to damage the internal components unless you are extremely wrong in your operating habits. The tubes are not made of $$$$$$$$ like more expensive ceramic tubes. They are inexpensive and quite literally pennies compared to say a 3cx800A7 or 3cx1500 tube over $1000 each.

Sometimes for a starter the best amp is the one with the cheapest tubes. I know you want robust and strong tubes, so if you don't want to learn by blowing up a few 20 dollar tubes then I recommend an amp that uses the 3cx1200A7. It is nearly indestructible except under the worst operating conditions. However, an amplifer that can run that tube is going to set you back minimum of 3000 dollars with the replacement tube over $1200-1300 each.

Good luck



Title: RE: Which amp to start with?
Post by: VK3BL on January 14, 2017, 02:25:58 AM
Thinking that 1000 watts would be good. I have had issues with RF in the house tripping GFCI, etc but when I went to the vertical it seems to have gotten better (although my computer monitor still goes wonky with 100 watts)

The long and the short of it is if you are having RFI problems at 100 watts, it will be a nightmare at 1000 watts.  More than likely, whatever is causing the RFI will burn out.

It sounds like you have an antenna efficiency problem.


Title: RE: Which amp to start with?
Post by: ZENKI on January 14, 2017, 03:24:26 AM
Verticals are notorious for generation a  strong near field  equipment and noise which is close enough to pick up and radiate problems

Can you support a open wire fed 40 meter dipole, or even a 30 meter dipole  fed with  balanced coupler or  even a T match with a good external 1:1 balun.

Another option would be to use a Vertical like the Hygain AV640  up high on  a pipe or Rohn 25 section 20 to 30ft would be enough to give you a better signal and decrease the field strength.

If you can do that,  and then get a small Amplifier like an Ameritron AL80B, I dont think you will have  the trouble that you are having.

If you want to get on 80  and 40  only a coil loaded dipole will work a lot better for short contacts within the USA


Title: RE: Which amp to start with?
Post by: W8JX on January 14, 2017, 04:05:50 AM
I suggest a few things. First change antenna as non resonant antennas are not efficient and are prone to common mode RFI too. These multi-band (via a tuner) non resonant verticals look good in ads but they are for convenience not performance.  I suggest you try a Hustler 6BTV placed as far from house/shack as possible and what ever radials you can fit in (they do not have to be a resonant length on ground). Next on amp, if you had a RFI problem, it will get much worse with power. Avoid a AL811 series amp. They are a over rated POS and eat tubes very easily (because of over rating). If you want a amp, for about same money as a AL 811 (or a bit more) you can get a used AL-80 series amp. It is a rock solid 850+ watt amp. you can push it to 1000 or so but remember that even from 850 to 1100 is not quite one db and will make no difference down range (the extra 250 watts is far more a state of mind/ego than a meaningful help down range) If you can find a clean SB-200 that has been rebuilt it is far more rugged/solid 500 to 600 watt amp than ANY AL811 amp hands down. (two 572's have 50% more safe dissipation than four 811's)

Scrap current antenna first then consider a amp.


Title: RE: Which amp to start with?
Post by: W9IQ on January 14, 2017, 04:12:57 AM
Chris,

After reading your description of your antenna installation in the Elmers section, I would encourage you to go through the RF Exposure assessment procedure. My guestimate is that it will not be safe (or legal) for you to use a 1 kW amp in your situation.

If you do pass the assessment, you should then first improve your grounding/counterpoise situation and evaluate the suitability of your 9:1 unun and coax for the anticipated power with additional consideration for your elevated SWR.

- Glenn W9IQ


Title: RE: Which amp to start with?
Post by: VK3BL on January 14, 2017, 05:22:56 AM
Chris,

After reading your description of your antenna installation in the Elmers section, I would encourage you to go through the RF Exposure assessment procedure. My guestimate is that it will not be safe (or legal) for you to use a 1 kW amp in your situation.

If you do pass the assessment, you should then first improve your grounding/counterpoise situation and evaluate the suitability of your 9:1 unun and coax for the anticipated power with additional consideration for your elevated SWR.

- Glenn W9IQ

VK is probably different to you guys, but at HF frequencies with a vertical 1000 watts would be fine in terms of exposure so long as you are a good 20-30 ft from the antenna.  The best way of achieving this if you are too close to the antenna is to elevate it 20-30ft.



Title: RE: Which amp to start with?
Post by: VK3BL on January 14, 2017, 05:43:53 AM
I have a very tight lot, with a 50ft vertical above a 9:1 unun running 100watts. I really do not have much antenna options, no space for a ground plane array either.

A few things here as well:

1) If you don't have a ground plane, and you're using a vertical monopole, your feed line is your ground plane.  Thats why you still have RFI issues with the computer monitor.

2) Unless your feed line is sufficiently long (think 100ft), you are almost certainly going to fry that balun on one of the bands you try @ 1000 watts.  Contrary to popular belief, baluns - especially 'ratio' baluns - generally only provide optimal performance on a few bands best case scenario.

3) What antenna tuner are you using?  Even my Palstar AT2K can't take more than 250 watts if I try to tune up a 52ft ladder line fed dipole on 80M - the antenna is simply too short electrically, presents a low impedance to the tuner, cooks the inductor and arcs a cap.  You may fair better if you have a less efficient antenna system (you do).

To put things into perspective, even a full 1/4 wave mono band vertical monopole with the typical 4-16 radials fed with 30-50ft of coax is going to be hard to get past 50% efficiency in a typical installation.  If its built well, the power loss won't be in components, but rather the feed line and the earth surrounding the antenna.

In summary, as much as I love amps, I just can't recommend you add one to your station at this stage.  You are already reporting RFI issues at the 100 watt power range, and I highly suspect you'll blow something up if you run at 1000 watts.  You really need to get some radials down.

If you really must have an amp, my advice is to pick a band and setup an efficient mono band antenna, or a G5RV variant.  I assume you can't install a dipole, so as far as verticals go, the best bet is probably something like a 43ft vertical with the tuner at the feed point (think MFJ-998RT) and a 1:1 current balun just before the ATU.  You would still need radials. 

If you truly cannot manage a horizontal dipole or a vertical with 8+ radials, your only real option is a vertical dipole.  Gap antenna and a few other companies make them, and they truly are your only option if you want to run 1kw into a vertical with no radials and not suffer RFI.

As far as first amps go, a very good to excellent condition second hand AL-80B should be at the top of your list.  Run it at 800 watts and it will take a licking.  They are a (relatively) modern design, and full manufacturer support including all replacement parts are available.  The AL-80 series mainframe is simple to work on, and the 3-500ZG is a monster tube with 500 watts+ of dissipation.

Only consider an AL-811 series if funds are really limited, and you only intend on once a week SSB Phone usage.  Tube life will be pretty short irrespective of how hard you drive them, as they are biased to idle at around 35-40 watts per tube.  Thats over half the tubes rated dissipation (45w CCS / 65w ICAS) just in idle bias current, and its continuous.  On the other hand, the tubes are plentiful and cheap, but you should only expect 500-1000 hours from a good set.

Much better to buy an AL-80B if you can.  It will literally pay for the extra cost in tube savings with a few years or regular use.


Title: RE: Which amp to start with?
Post by: W8JX on January 14, 2017, 06:40:26 AM
Only consider an AL-811 series if funds are really limited,

If funds are that limited do not waste money on a AL811 and save for a real amp. That being said though a SB200 in good order can be had for a lot less than a new AL811 and is a MUCH better amp. The fact they are still in use and demand nearly 50 years after they were first designed tells you a lot about the ruggedness of design.


Title: RE: Which amp to start with?
Post by: W9IQ on January 14, 2017, 06:41:22 AM
Quote
VK is probably different to you guys, but at HF frequencies with a vertical 1000 watts would be fine in terms of exposure so long as you are a good 20-30 ft from the antenna

The FCC requirements for analysis are more prescriptive and are required to be done at these power levels.

- Glenn W9IQ


Title: RE: Which amp to start with?
Post by: W2BLC on January 14, 2017, 06:57:52 AM
1. The SB200 is too old - worn wafer switches and other stuff are showing their age.
2. You can get the AL811 with 572B tubes - makes it a little stronger. No increase of power.
3. Dipoles up to 50% size reduced with coil loading work well - just are narrow banded.
4. I now have a solid state amp, due to the reduced size and weight. Puts out 500 Watts.
5. First 500 Watts is the most important. I have found no times when I cannot make contacts.
6. More powerful amp requires bigger size, increased weight, and probably tuning (tube type).
7. If you can stand the size and need for tuning, then a tube amp will do more for you cheaper than solid state.
8. Voltages in a tube amp can kill you!
9. House wiring must be able to support an amp. A 220 dedicated 20 amp line is recommended.
10. Plugging into the wall plug 110 won't do much except cause modulated lamps.
11. Improve the antenna situation before putting an amp in. Much cheaper than an amp.



Title: RE: Which amp to start with?
Post by: KB1SNJ on January 14, 2017, 07:17:43 AM
all great info thanks.     the base of my vertical is 10-12ft from where I sit inside the house, and on the fence line. If I use a shorter vertical, and assuming I can not radiate from the feedline, it could start higher, above the roof and away from the property edge. (see pic).  as someone who has not operated an linear amplifier, i appreciate the advice. such as the SB200 idea, and that the first 500 watts gets the most bang for the buck. A quick check on fleabay shows sb200's going for 300-500 generally, often near the top of that range. how do those sound? why is it 'MUCH better' than AL811? in what way?

thanks for all the info

Here is my small lot property layout:  https://flic.kr/p/QZj9r9





Title: RE: Which amp to start with?
Post by: N8FVJ on January 14, 2017, 07:31:56 AM
Two amps come to mind. Ameritron AL-811 with three 811A tubes or Heathkit SB-200 with Harbach upgrades. 500 watts out from the Ameritron AL-811 and 600 watts from the Heathkit.

You can retrofit Chinese 572Bs in the Ameritron three tube AL- 811. The three tuber Ameritron shares the same power transformer of the four tube AL-811H Ameritron, thus you can get 600 watts out of the Ameritron 811A with three 572Bs. The Chinese tubes have proven to be reliable.


Title: RE: Which amp to start with?
Post by: W8JX on January 14, 2017, 07:53:54 AM
The SB200 is too old - worn wafer switches and other stuff are showing their age.

If this was really true all SB200's and 201's would be in junk pile but they are not. (neither are SB220's of same age) I own a SB200 and it is still nice and tight. Quality of switchs when new was much better than what is used is a AL811

You can get the AL811 with 572B tubes - makes it a little stronger. No increase of power.

Not quite true. While you can swap in 572's you do not need as many and you can increase power because you can safely run a 50% higher plate current. 3 572's can handle more power than a AL811 power supply can make and while safely make more power than 4 811's (putting 4 ea 572's in a AL811H is a waste of money as 3 will make just as much power as power supply cannot begin to exploit 4 of them as 811H use exact same power supply as base 811)  You could even try 2 ea 572 in a AL 811 and use same current setting as in manual as two 572's can handle more than 3 811's and still have over twice the safe dissipation as 3 ea  811's and should be able to get 450 watts or so. (I mention this to show what a weak amp tube a 811 truely is. Nothing remotely HD about it)  Furthermore when compared to a SB 200 the 200 has 50% higher plate voltage than AL811 and can use 572's far more efficiently. Also same money spent to retube a AL 811 a few times or upgrade to 572's will easily buy a used AL80 (a real amp). AL 811 look cheap to buy but when you factor in tube replacements it is not (just like inkjet printer look cheap but you pay a lot for ink for it)

I now have a solid state amp, due to the reduced size and weight. Puts out 500 Watts.

SS amps are not as rugged or forgiving and require very low SWR. A tube amp can run with 2 to1 or so SWR without any concern

First 500 Watts is the most important. I have found no times when I cannot make contacts.

 I say first 600 to 800 watts mean most for a few reasons. First 600 watts is a little over 6 db (one S-unit) and 800 watts is 9 db (1 1/2 S-units). Going from 800 to legal limit (though many go way beyond that today) is abt 3 db and not a big deal (and this is way many quietly run far more power)

If you can stand the size and need for tuning, then a tube amp will do more for you cheaper than solid state.

In bang for buck and ruggedness you cannot beat a tube amp (except overrated POS 811 amp which should be avoided)

Voltages in a tube amp can kill you!

I have never heard of someone being killed by a tube amp but thousands have died from 120 volt wall current.

House wiring must be able to support an amp. A 220 dedicated 20 amp line is recommended.

Not really, I have used a 15 amp 240 volt circuit feed with 14/3 for over 20 years and never had a problem. It will easily feed a legal limit amp and 14 ga is a bit easier to route in tight places too. (you do not really need a 20 amp circuit unless you plan to regularly exceed legal limit by a good bit)

Plugging into the wall plug 110 won't do much except cause modulated lamps.

It depends on size of amp. A SB200 plays nicely on 120 but if you get a AL80B and plan to run it hard you want a stiff 120 volt circuit. Also you have to look at total draw on circuit. If you are using a old technology linear supply you wil draw close to 500 watts (a bit over 4 amps) from wall to power a SS rig at 100 watts due to efficiency losses. Use a switching power supply and peak draw for rig from wall will be close to 3 amps and every little bit helps with a amp on a 120 volt circuit

Improve the antenna situation before putting an amp in. Much cheaper than an amp.

True but not easy to get 6 to 9 db on HF with a new antenna unless other one is very bad.


Title: RE: Which amp to start with?
Post by: KB4MNG on January 14, 2017, 08:54:34 AM
IMO the best amp on the market is the al 80 b. Simple design, one tube that is easily obtainable and priced fairly, and a great company. Yeah, there are other amps that are much better but they are expensive and complicated. If you have a solid state radio, I would really consider the als 600, also another great amp for the same reasons. I have both.

Stay away from the 811 or 572 b tube amps. You can get tubes but they are very expensive and not as robust as the 3-500 tube that will probably last your life time it taken care properly.

There are some heathkit models that employ the 3-500 tube that are really good if you can get them at a good price. It may require some repair or maintenance.


Title: RE: Which amp to start with?
Post by: W8JX on January 14, 2017, 09:18:55 AM
Stay away from the 811 or 572 b tube amps. You can get tubes but they are very expensive and not as robust as the 3-500 tube that will probably last your life time it taken care properly.

While I agree that a 811 is not robust at all not so with a good 572. There are some old 572's 40 years old still going strong and some high quality reasonably priced 572's on market now too.(I have 4 ea 572's in my Detron dated 1985 that still will make 1000 watts without a fuss and 55 to 60 watts of drive too)  As far as a modern 3-500 lasting a lifetime, not hardly as not are like tubes made 40 years ago. While they can last many years if used properly the AL 80B does not properly cool it (at rated 500 watt dissipation the tube is supposed to have a chimney with air flowing through socket and over tube, not just a small muffin fan blowing across it) and to run 1000 watt or more with a AL80 you have to exceed tubes ratings and cooling and it will shorten life. That being said a AL80b is a solid 850 watt amp and a but marginal at 1000 to 1100 watts because tube life will suffer.


Title: RE: Which amp to start with?
Post by: K1HMS on January 14, 2017, 10:45:28 AM
I would look for a Al-80b for good, clean, and reliable power. Second choice would be a ALS-600, but don't over drive it and watch the match. Forgetting to turn the band switch or tturning down the drive will cost you.

But for the same money you would likely have more fun with a Hex beam due to all of the activity you would hear and work.


Title: RE: Which amp to start with?
Post by: VK3BL on January 14, 2017, 06:23:31 PM
While I agree that a 811 is not robust at all not so with a good 572. There are some old 572's 40 years old still going strong and some high quality reasonably priced 572's on market now too.(I have 4 ea 572's in my Detron dated 1985 that still will make 1000 watts without a fuss and 55 to 60 watts of drive too)  As far as a modern 3-500 lasting a lifetime, not hardly as not are like tubes made 40 years ago. While they can last many years if used properly the AL 80B does not properly cool it (at rated 500 watt dissipation the tube is supposed to have a chimney with air flowing through socket and over tube, not just a small muffin fan blowing across it) and to run 1000 watt or more with a AL80 you have to exceed tubes ratings and cooling and it will shorten life. That being said a AL80b is a solid 850 watt amp and a but marginal at 1000 to 1100 watts because tube life will suffer.

I agree.  The 811a is not in the same league as the 572b.

Despite what you may find written over at W8JI's website, neither the filaments nor the grids are the same as the 811A. Any cursory glance at both tubes will show this.



Title: RE: Which amp to start with?
Post by: N3DT on January 14, 2017, 07:01:42 PM
I can vouch for the 80B. It's a solid amp with a good tube and can be had for under $900, sometimes delivered. I've heard of them for much less. Nice if you can find local and shown. No disappointments if it works. I'd stay away from the older amps, they're even older than the 80B and will most likely have issues that you'll spend more money on than if you just bought an 80B that is guaranteed to work and still in production. Puts out a solid 700-800W which is the sweet spot before you have to go to something better than RG8X. As far as your vertical, I never met one I liked. Get a real antenna, dipole at 20' if that's what you can do. Stick to a single or 2 bands for a while, 40 and 20 are good choices with 40 CW the prime choice. You can work the world on 40 CW, especially with the sunspots where they are. Improve your antenna first, it's cheap. Power is nice but only gets you a few S units at best and you won't hear any better. A better antenna will get you there both ways, RX and TX, before the amp. Believe me.


Title: RE: Which amp to start with?
Post by: KB1SNJ on January 14, 2017, 09:23:24 PM
Ok I have listed in my notes every amplifier suggestion and antenna suggestion, and noted the tuner consideration and RF management.

because of the replies I can now at least fundamentally see the basic areas to address and I agree that the antenna needs to be dealt with.

here's a few thoughts and questions. I dont necessarily need answers as this was an amplifier topic and I got some great suggestions thank you! but these things are unknowns as to what would be best.

It also makes me wonder how irregular a ground plane can be.

For example I can bury radials all around the house perimeter (and I just realized that I have 2 fairly short radials off the vertical now one running East, one running west, and a 8ft ground rod right under it). my house is roughly 20x30 and against the boundary on 2 sides, so I can run a radial around the perimeter like a loop, what would that do for RF coming back as well as a pattern if it were under a vertical roughly in the middle above the house?  and does the vertical have to extend down to the ground?  another question is that my property is 40ft wide and faces east west the long way. I suppose I could erect poles at each side maybe at the back lot corners,  and that would span 40ft with the broadside facing east-west.  I wonder what min height would be needed? (I will look that up). what would it take to work 160-6 on a horizontal wire/dipole that spans only 40ft? use traps or coils? that end of my lot faces west, I suppose I could add a reflector wire some distance forward (east) to put some gain to the west?



as to the tuner, I didnt think of the fact that the tuner is between the amp and antenna feed point (duh) and must handle the full power. another cost.

the antenna suggestions are as usual confounding because of the constraints of my lot and building shape. at least i have the 2 big trees and an unlimited budget (KIDDING!)

originally this was "I have an antenna that I can at least match on most bands. if its not very efficient, I can add power".  now I know that wont be optimal due to RF (lack of ground plane), and other things.

btw when I had my bent G5RV over the house RF was worse, tripped a GFCI and fried my router as well as jammed my computer monitor requiring it to be power cycled. the new vertical is not as bad, only the monitor is affected (and the headphone mixer cant be used). so there's still RF inside despite the ground rod and two radials.








Title: RE: Which amp to start with?
Post by: KK4YDR on January 14, 2017, 10:09:54 PM
I love how these "What should I buy" threads turn into whos opinion is more important than the next and how much one thing sucks more than another and how it goes around and around.

Just get what you can afford. Get a better or modify your existing antenna to be better. And just be happy.

I recommend the junk 811 as so many people call it because I owned one in the past and it wasn't junk in the least darn bit. I only sold it to get a legal limit amp to upgrade. It was a good little beginner amp for sure.


Title: RE: Which amp to start with?
Post by: KB1SNJ on January 14, 2017, 10:13:32 PM
I've found the replies very helpful. They showed me that i cant just buy power and be happy because of likely RF issues and it's about the antenna before the amp. So I appreciated all the info.


Title: RE: Which amp to start with?
Post by: VK3BL on January 14, 2017, 11:29:50 PM
btw when I had my bent G5RV over the house RF was worse, tripped a GFCI and fried my router as well as jammed my computer monitor requiring it to be power cycled. the new vertical is not as bad, only the monitor is affected (and the headphone mixer cant be used). so there's still RF inside despite the ground rod and two radials.

I've operated a station with an antenna a similar distance - around 20ft.  I did have one brand of access point that would lose its settings when it TXed at QRO, but it was fed with a 15ft network cable so its not surprising.  Everything else was fine though, although if I used a set of headphones with the rig I'd occasionally get noise in them while TXing, but that was solved with a few turns through a ferrite core.

Could you run a 52ft G5RV without bending it?  That would give you better balance, and you could use all bands 40M up, and probably 80M for local contacts at lower.

If you still have the bent G5RV up, it would we worth seeing if a different balun improved things.  A properly designed 1:1 current balun should keep RF off the outside of the coax and minimal (other than radiated) in the shack.

Keep digging, its definitely possible to operate QRO close to your antennas.  DXPeditions do it all the time, as would many amateurs.

For a balun, buy a FT240-43 core from Fair Rite, and wind 12 turns of LMR-195/RG-58 round it.  Thats as close to the perfect 'do everything' 1:1 balun as you're going to get, and its good for well over 1Kw continuous.

You can add the aforementioned balun to your existing setup, just after the 9:1 at the feed point.  The 9:1 is maybe/probably helping with matching on some bands, but it is likely its doing little to stop RF getting back into the shack via the coax.



Title: RE: Which amp to start with?
Post by: W9IQ on January 15, 2017, 03:09:59 AM
Chris,

Since you are in a compromise situation, I would recommend running any radials you can. It will likely improve the efficiency of your antenna and it may reduce RF in your house. The antenna pattern won't be predictable but it is better than the alternative.

Try to keep the bottom of the vertical wire at the same height as where all the radials meet.

A good 1:1 choking balun where the coax connects to the antenna will also help reduce RF in the house.

- Glenn W9IQ


Title: RE: Which amp to start with?
Post by: W9IQ on January 15, 2017, 03:29:56 AM
Quote
Keep digging, its definitely possible to operate QRO close to your antennas.  DXPeditions do it all the time, as would many amateurs

While this is probably true, it does not properly recognize that in the US, a ham wishing to operate QRO is required by FCC regulations to carry out an RF exposure assessment. If the RF exposure is above the regulatory limits, the licensee is required to bring them into compliance before operating QRO.

- Glenn W9IQ


Title: RE: Which amp to start with?
Post by: W8JX on January 15, 2017, 04:32:02 AM
I recommend the junk 811 as so many people call it because I owned one in the past and it wasn't junk in the least darn bit.

Without doubt the AL811 is the cheapest built and most troublesome amp on market by far. To suggest otherwise is very misleading. Landfills have thousands of burnout/melted 811 tubes in them from AL 811 amps. If you use one and run it 30% below rated output it may last for a while but it is very easy to damage tubes in it. The funnest part of this is that Ameritron makes a 800 watt rated AL811H and a 850+ watt rated AL80B yet the AL80B has roughly twice the transformer mass and about 250% more safe plate dissipation in one tube than a AL811 has in all 4 and yet some cannot connect dots and see what a cheap over rated amp it is. There is no other amp made in last 40+ years (except for a few sweep tube amps) that regularly exceeds tube rating for "normal" rated operation. None! If old Heathkit SB200 had been built as cheap and over rated as much as AL811's they would of disappeared decades ago rather than still being quite viable today. It was rated at about 600 watts out with a safe dissipation of 320 watts. The 600 watt AL811 has a safe continuous dissipation of 135 watts. Which is a real amp?


Title: RE: Which amp to start with?
Post by: N8FVJ on January 15, 2017, 06:50:28 AM
Quote: 'I have never heard of someone being killed by a tube amp but thousands have died from 120 volt wall current.'

I heard. The ham was on the air in the 1990s on 3898 when it was famous. In the round table a ham did not come back. It was later found he tripped and his hand entered the top of an uncovered home brew amp. He was electrocuted.



Title: RE: Which amp to start with?
Post by: W8JX on January 15, 2017, 07:19:59 AM
Quote: 'I have never heard of someone being killed by a tube amp but thousands have died from 120 volt wall current.'

I heard. The ham was on the air in the 1990s on 3898 when it was famous. In the round table a ham did not come back. It was later found he tripped and his hand entered the top of an uncovered home brew amp. He was electrocuted.


Anyone stupid enough to use a HV amp in normal operation without a cover on it is asking for trouble. It is not the fault of it being a HV amp but rather the fault of the operator. Hard to make it idiot proof. Plus if it was a commercially built amp it likely has a HV interlock on cover that you have to disable for this to happen


Title: RE: Which amp to start with?
Post by: KB1SNJ on January 15, 2017, 10:46:58 AM
Regarding the RF issues, I had bought some snap together ferrites years ago and tried them to keep the RF out of the headphone mixer and monitor to absolutely no avail. I think ferrites are tricky, there's different compounds and shapes resulting in varying electrical properties. I had another issue never resolved, with a 12dc-120vac voltage inverter trying to stop the hash from getting to an older tube receiver in my camper (which is quiet on wall power). Tried wrapping the power cord through #43 and #61 Ferrites did nothing.  Adding brute force EMI filters did nothing. Buying a better inverter (samlex) and grounding it, cut the noise about in half. Then I ordered a EMI cord http://emceupen.com/_files/content/pdfs/na201_201507161230060084.pdf
and again, wall power = quiet, inverter power sends hash to the receiver. No noise when running the inverter but radio is on wall power (unless its very close). So the above EMI cord, or 43 and 61 ferrites did not stop whatever is travelling down the power cord.

So my track record on stopping RF from my antenna from getting into things, or whatever is coming from the inverter is batting a zero.

As to the HF antenna issue, obviously I do need to implement an antenna that radiates all the RF and not from the feedline back into the shack/house. Because even if ferrites etc worked to block it from my equipment, I would need a forklift load of them to cover all the cat5, power cords, speaker cables, and everything else.

As to the inverter noise issue, I was surprised at how resilient it really is, making it through ferrites, brute force filters, and that very good EMI power cord!

BTW, is that noise from the inverter RF or something else?





Title: RE: Which amp to start with?
Post by: W9IQ on January 15, 2017, 12:55:13 PM
Chris,

RFI problems are often by their nature often difficult to cure. There are engineering professions that deal exclusively with EMI and RFI and there can be very frustrating days even for these well practiced engineers.

Based on your description of your antenna, I would work on reducing common mode current as this will follow your coax into your shack and it brings your RF (and effectively your antenna) that much closer to the balance of the house. Adding a quality choking balun at the feedpoint of your antenna and adding radials (counterpoise) to your antenna will help to reduce the common mode current.

Secondarily, your antenna is located very close to your house. You are therefore subjecting many electrical / electronic things in your house to high RF levels. Most consumer electronics where never designed to work properly in such conditions. Sometimes you get lucky and things work. Other times they get quirky. The most effective cure is to reduce the RF in the house. Possible solutions (in addition to reducing common mode current): move the antenna further away, use a directional antenna pointing away from the house, and lowering your transmit power. Failing success with these, you can attempt to apply counter measures on each effected device with varying degrees of success.

To your inverter question, yes the noise is RF.

- Glenn W9IQ



Title: RE: Which amp to start with?
Post by: KB1SNJ on January 15, 2017, 02:25:25 PM
Thanks Glenn, very big help. Im starting to get it. Looked at this page regarding choke at feedpoint.

http://palomar-engineers.com/antenna-products/1-1-balun-kits/choosing-a-feedline-choke

 I'd appreciate suggestion on the very best broadband feedpoint chokes available ready to go that I can procure.

After that then I can experiment with some homebrew ideas and have something to compare to.

Hopefully in my case one choke will mitigate the RF common mode coming back although that site did describe situations where they need to be added at intervals (Im imagining with long feedlines).


Title: RE: Which amp to start with?
Post by: NI0C on January 15, 2017, 03:38:20 PM
Here's what I use: http://www.balundesigns.com/feedline-isolation-baluns/

I like that Balun Designs publishes graphs of choking impedance versus frequency, so you know what performance you are getting.


Title: RE: Which amp to start with?
Post by: KB1SNJ on January 15, 2017, 05:07:20 PM
Cool thanks. Which model? Single or dial core, 1-31 or 1.5 to 54?

Im going to assume 1.5 to 54 to cover 6m, dual core.


Quote from: NI0C li :)nk=topic=113083.msg974213#msg974213 date=1484523500
Here's what I use: http://www.balundesigns.com/feedline-isolation-baluns/

I like that Balun Designs publishes graphs of choking impedance versus frequency, so you know what performance you are getting.


Title: RE: Which amp to start with?
Post by: VK3BL on January 15, 2017, 05:27:55 PM
Cool thanks. Which model? Single or dial core, 1-31 or 1.5 to 54?

Im going to assume 1.5 to 54 to cover 6m, dual core.


Quote from: NI0C li :)nk=topic=113083.msg974213#msg974213 date=1484523500
Here's what I use: http://www.balundesigns.com/feedline-isolation-baluns/

I like that Balun Designs publishes graphs of choking impedance versus frequency, so you know what performance you are getting.

With your current setup already in place Chris, my suggestion would be to purchase a FT240-43 core, and wrap your coax round it as many times as you can.

Steve G3TXQ has published the design graphs, you can see them here:
http://www.karinya.net/g3txq/chokes/

I have used both his 12 Turns on FT240-43 & 11 Turns on 2x FT240-52.  Both provide excellent common mode blocking performance as advertised.

Given that you can pick up a FT240-43 core for ~$10 USD, and just pass your coax through it a few times, I'd try that first before investing in a commercial version of what you can probably make yourself with Steve's published designs.

The 11 Turns on 2x (stacked) FT240-52 cores is probably the closest to an 'ideal' balun you can get, it is however a bit more costly to purchase as you need 2x 52 material cores.  However, if wound with teflon coax, it should be good for well over 2kw continuous into reasonable (SWR < 5:1) loads. 

The current 11T/2xFT240-52 Balun I use tested fine (no heating or insulation breakdown) at 1.3Kw into my dummy load.  It has not failed in service at 400 Watts PEP with ANY load.

By comparison, my a commercial Kenpro '1Kw CW' balun I had failed instantly when I tried putting 400 Watts PEP into a non resonant load.

I can't stress enough how much the Amateur community owes Steve G3TXQ for his work testing various designs and publishing them. Thanks Steve, hope you're well!


Title: RE: Which amp to start with?
Post by: N3DT on January 15, 2017, 05:55:37 PM
You can get those 240-43 ferrites from Mouser at a lot better price than Fair-Rite. I can come up with a number if I try. Let me look at my previous orders. I got 6/8 of them as I remember. You can also put them in multiple places along the coax. Especially at the entrance of the coax to the house, not just at the antenna. I use them, but my antennas are at least 120' away from my house and the shack is mostly underground, so that helps a lot, I have no rf in the shack with an 80B. Can you move your station to your basement? It actually may help. I like TXQ's choke plans, but then most of my coax goes underground to my shack so that also helps.


Title: RE: Which amp to start with?
Post by: KB1SNJ on January 15, 2017, 06:05:58 PM
 thank you yes any source and part number information would be great. I did notice that Amazon has them for about ten bucks including shipping but if I get an order from Mouser I can be more confident of the authenticity and combine the shipping of a larger amount of them. and I saw that the comment that the number 52 toroids, doubled up would be ideal I'm not exactly sure why but it sounds like the 43 would be okay too.

 as to moving the shack to the basement,  I wish I had a basement, that's the one thing I really don't like about my house and probably the main reason that I hope to have a different house someday there's no basement and the house is extremely small. On my last house we actually installed a basement. Funny story an acquaintance of mine who moves houses stopped by and casually suggested that we could lift the house, move it, and when I have a hole with four concrete walls he could put it back. Said he could do it "next Wednesday". So I said "ok". The following Tuesday by the time my wife got home from work it was a little bulldozer and some iron beams sitting on my side yard and she asked what it was for I just told her don't worry about that.  But tomorrow when you come home from work the house may look a little different.  Oh It did! 

But our current house is built on a slab and that's not an option. Besides I'd really like to prevent RF flying around all over the place where it's not supposed to and protect the consumer electronics etc.  I really like the idea of any emanating RF to come from the antenna in the direction that it is supposed to go, and learning something in the process!





Title: RE: Which amp to start with?
Post by: NN2X on January 15, 2017, 07:45:28 PM
SB 220!


Title: RE: Which amp to start with?
Post by: KB1SNJ on January 15, 2017, 08:46:58 PM
SB 220!

Whats the main difference with the SB200?


Title: RE: Which amp to start with?
Post by: VK3BL on January 15, 2017, 10:42:35 PM
thank you yes any source and part number information would be great. I did notice that Amazon has them for about ten bucks including shipping but if I get an order from Mouser I can be more confident of the authenticity and combine the shipping of a larger amount of them. and I saw that the comment that the number 52 toroids, doubled up would be ideal I'm not exactly sure why but it sounds like the 43 would be okay too.

Have a look at Steve's graphs.  The 2x52 has a wider bandwidth and handles more power.  The 1x43 is very broadband for a single core, but not as much as a 2x52 stack.  Cost difference, at least here in VK, however.


Title: RE: Which amp to start with?
Post by: KB1SNJ on January 15, 2017, 10:54:17 PM
Was JUST looking at that!  :)   But I'm not quite sure which way the colors go, not sure what values on the color key at the bottom. is that resistance to common mode current, and higher (such as green) is better?  So theoretically all green from 160-10 would be ideal?

also, do these cores come in different sizes? is the FT240-43 also a size as well as compound? The chart mentions turns and coax type for example 17 turns of RG58, so I need to get a large enough toroid core to accept rg58 17 times. I just dont know if the FT240 is a size spec or if I have some math to do. I suppose I could just cut out some cardboard with 35mm ID, get some RG58, and see that way!

The chart represents apparently a lot of work as u said, and it is very helpful once I can interpret its basics.  

sorry for the dumb questions and thanks for the info. if I can get the RF situation acceptable then its back to the amplifier choice. the 80b seems to get a lot of votes as does the old SB's


thank you yes any source and part number information would be great. I did notice that Amazon has them for about ten bucks including shipping but if I get an order from Mouser I can be more confident of the authenticity and combine the shipping of a larger amount of them. and I saw that the comment that the number 52 toroids, doubled up would be ideal I'm not exactly sure why but it sounds like the 43 would be okay too.

Have a look at Steve's graphs.  The 2x52 has a wider bandwidth and handles more power.  The 1x43 is very broadband for a single core, but not as much as a 2x52 stack.  Cost difference, at least here in VK, however.


Title: RE: Which amp to start with?
Post by: VK3BL on January 16, 2017, 12:30:17 AM
Was JUST looking at that!  :)   But I'm not quite sure which way the colors go, not sure what values on the color key at the bottom. is that resistance to common mode current, and higher (such as green) is better?  So theoretically all green from 160-10 would be ideal?

also, do these cores come in different sizes? is the FT240-43 also a size as well as compound? The chart mentions turns and coax type for example 17 turns of RG58, so I need to get a large enough toroid core to accept rg58 17 times. I just dont know if the FT240 is a size spec or if I have some math to do. I suppose I could just cut out some cardboard with 35mm ID, get some RG58, and see that way!

The chart represents apparently a lot of work as u said, and it is very helpful once I can interpret its basics.  

sorry for the dumb questions and thanks for the info. if I can get the RF situation acceptable then its back to the amplifier choice. the 80b seems to get a lot of votes as does the old SB's


1) Green 160-10M would be ideal, correct

2) They do, but FT240 means its a 2.4" diameter core, so its not as hard as you might think.

No worries :)


Title: RE: Which amp to start with?
Post by: W8JX on January 16, 2017, 04:52:48 AM
SB 220!

Whats the main difference with the SB200?

The 220 uses a pair of 3-500z tubes vs a pair of 572's in 200. The SB 220 can make about 1000 watts out without much fuss and is only limited by its power supply (voltage and current)from being a true legal limit amp. (when it was built/designed the limit was 1000 watts)


Title: RE: Which amp to start with?
Post by: N3DT on January 16, 2017, 07:53:52 AM
Sorry, yes, FT240-52, I was relying on my defective brain to remember. Mouser PN 623-5952003801. If you look at TXQ's chart, the black/green bar is the one you're looking for, but that doesn't mean it won't work outside that range to some degree. FT=ferrite torroid, 240=2.4" as was said and -52 is the mix. You can pick up a fairly recent ARRL Handbook for a few bucks and there's a wealth of information in there about the Iron core and FT's, as well as lots of other good radio information. I see the Mouser price has gone up, seems I got them for around $6 in 2014. I also would suggest getting some RG400 off ebay for a few bucks to wind the 2 cores, that way, they'll handle anything you can give them and you don't have to worry about melting the coax with soldering. I use the 4" square weather proof electric boxes from Lowes or HD to put them in with #10 SS hardware for the antenna and SO239 for the coax. They're a bit tight but do-able. Larger boxes are available, but the price goes up too.

You're in a tough situation. No amount of reduction of the RF on the trans line or other things is going to stop the antenna from radiating into your house because the antenna is so close, even with a directional antenna. Vertical separation is your best bet. You might want to consider just running lower power and using the most effective antenna you can get up and dealing with it until maybe your situation changes. Lots of people use low power as a challenge. You might also consider a Mag Loop for RX and transmitting on something else, but with low power the Mag Loop is a cheap (home brew) alternative too. Try to get up different antennas to see what works, there's never enough antennas. I once had an inverted L that was right outside my shack and it too had horrible RF in the shack with just 100W, especially on the higher bands. If I were you, I'd concentrate on the RX end. If you can't hear them, you can't work them. Good propagation is your friend also.


Title: RE: Which amp to start with?
Post by: KB1SNJ on January 16, 2017, 08:18:18 AM
thanks for the advice.  it seems often I can hear them and they cant hear me, or can barely hear me. as a result of information in this topic I figure on lower power but definitely wish to try more than 100w. 

also, if I could erect a free standing vertical, I could use the front yard but there's my house power coming across there so it would have to have at least a couple guys to prevent ever falling that direction (right?). of course if fiberglass then would that matter?

at any rate, I think I need to learn how to stop CM at the feedpoint and with that chart and the toroid info I am almost there. 

question: if I wanted to apply two ranges on the chart can I make both winded-toroids and install in series? I think I can just want to ask.

 is there any other way that the feedline can radiate RF in my house, when there is a choke?
how can I know there is no CM coming back?





Title: RE: Which amp to start with?
Post by: W8JX on January 16, 2017, 08:41:36 AM
thanks for the advice.  it seems often I can hear them and they cant hear me, or can barely hear me. as a result of information in this topic I figure on lower power but definitely wish to try more than 100w.

I know you have some coin in current vertical but it is a big part of your problem. Plug n Play verticals like that promise a lot actually deliver less and can have common mode RFI issues too by nature. And such a tall vertical is not going to have favorable lobes on 20m and above too. Before amp, scrap current antenna and try a different setup because adding power to current setup could cause a LOT of problems with RFI in your house and not really help that much. One more thing if you limited yourself to 40m for now and shortened antenna to 33 feet and removed 9 to 1 balun it should work pretty good without a tuner too. You could insert 9 to 1 and use tuner on higher bands and it would work better on higher bands being shorter too but given susspot cycle is declining 40m is a good place to be. 


Title: RE: Which amp to start with?
Post by: KB1SNJ on January 16, 2017, 09:04:37 PM
just a quick update, just ordered six #43 toroids (61mm) and two of the #52 toroids (60mm) which seemed around the 2.4" mentioned.

what is a good quality source for RG58 i will need to wind these?


Title: RE: Which amp to start with?
Post by: VE3TMT on January 17, 2017, 04:28:11 AM
Plug n Play verticals like that promise a lot actually deliver less and can have common mode RFI issues too by nature. And such a tall vertical is not going to have favorable lobes on 20m and above too.

I worked the world with 100w and my R7 at 15'


Title: RE: Which amp to start with?
Post by: W8JX on January 17, 2017, 04:52:15 AM
Plug n Play verticals like that promise a lot actually deliver less and can have common mode RFI issues too by nature. And such a tall vertical is not going to have favorable lobes on 20m and above too.

I worked the world with 100w and my R7 at 15'

A R7 is consider a resonate antenna as it does no need a tuner. A simple mast with a 9 to 1 and a tuner is not the same. Plus a 50 foot vertical will have unfavorable lobes on 20 and above. THose all band verticals look great in ads but do not perform well real world on all bands. Nothing magic about them.


Title: RE: Which amp to start with?
Post by: N3DT on January 17, 2017, 06:10:19 AM
Verticals, all you have to do is model one using your ground. They're fine if you live over salt water, but not if you have regular mountain dirt. Here's a modeled 40M GP at the same height as my 40M dipole. Which would you rather use?

(http://i251.photobucket.com/albums/gg287/DogTi/40%20gp%20vs%20dip_zpsqldmkkbp.jpg) (http://s251.photobucket.com/user/DogTi/media/40%20gp%20vs%20dip_zpsqldmkkbp.jpg.html)


Title: RE: Which amp to start with?
Post by: N3DT on January 17, 2017, 07:06:22 AM
I would seriously suggest RG400. Item 182283610795 ebay. 10' for $20. I forget how much it takes to wind a choke, but it takes a few feet. You'll never have to worry about it again.


Title: RE: Which amp to start with?
Post by: W8JX on January 17, 2017, 07:49:58 AM
I would seriously suggest RG400. Item 182283610795 ebay. 10' for $20. I forget how much it takes to wind a choke, but it takes a few feet. You'll never have to worry about it again.

I would use RG142. It uses a copper clad solid center conductor and weighs slightly less and would work nicely wrapping in a coil and easier to find and is a mil spec cable too. RG 400 is a little more flexible but both are fairly rugged with a PFTE dielectric and will handle legal limit with ease. We used a LOT of RG142 n aircraft in flight test. We also used its big brother RG 393.


Title: RE: Which amp to start with?
Post by: KB1SNJ on January 17, 2017, 11:35:52 AM
I have RG58 coming because thats what the chart chokes were tested with. I also bought a small amount of MilSpec RG400 to cover that base.

Is the 58 more likely to fail in some way (such as at higher power 600watts etc)?

As to the radiation pattern above, was that made in EZNEC or something else? Is there a free option thats easy to use for basic radiation pattern modeling? My property will require every tool available to develop a workable antenna.

As to that graph, the dipole is obviously way more efficient but i only have 40ft of width if the broadside is to be facing west. If I angle it southwest which may be better from here, then maybe I could get close to 50ft, and would need to erect support posts at the property line on each side, any recommendations on what to use? My house is about 15ft high at the ridge. Such  a scheme would put the horizontal right over my attic with all the network, hdmi, speaker, and house wiring everywhere. Same as when I had the G5RV above the roof.


Title: RE: Which amp to start with?
Post by: KB1SNJ on January 17, 2017, 12:11:16 PM
oops I misspoke, the RG58u is MilsPec Belden# 8262 RG58C/U 50 Ohm Copper Mil-Spec Cable Bulk

made offer on small length RG400, awaiting reply on that.


Title: RE: Which amp to start with?
Post by: W8JX on January 17, 2017, 01:35:22 PM
I have RG58 coming because thats what the chart chokes were tested with. I also bought a small amount of MilSpec RG400 to cover that base.

Either 400 or 142 would of worked as it is same size coax.

Is the 58 more likely to fail in some way (such as at higher power 600watts etc)?

You would not want to run a KW key down like RTTY with it. SSB would be fine. RG142 and 400 have a teflon dielectric and are better for winding chokes because closely wound coax gets much warmer with power than a single free run and 142 and 400 can handle 200c (almost 400F) without damage and therefore could easily handle a KW key down on HF.


Title: RE: Which amp to start with?
Post by: VK3BL on January 17, 2017, 05:20:33 PM
You would not want to run a KW key down like RTTY with it. SSB would be fine. RG142 and 400 have a teflon dielectric and are better for winding chokes because closely wound coax gets much warmer with power than a single free run and 142 and 400 can handle 200c (almost 400F) without damage and therefore could easily handle a KW key down on HF.

The only way to truly answer the question is to do the math.

You need to know your load SWR, and the cable specifications.

In my practical experience RG-58 & LMR-195 are both completely fine for over 1kW keydown into a resonant load. 

Put it this way, I stopped the test because both my dummy load and amplifier were getting quite hot, but the core and the cable had next to no heating.

Having checked the specifications, the RG-58 Chris has ordered is rated to 1400 Volts - well more than enough for a Kw into a decent SWR load.


Title: RE: Which amp to start with?
Post by: N3DT on January 17, 2017, 07:35:27 PM
I was really only suggesting the 400 because of the teflon and the silver plated mesh. It's much easier to work with than 58 when soldering with a big iron, which is usually needed, at least the way I do it. The 58 will melt in a heart beat. That's all.


Title: RE: Which amp to start with?
Post by: VK3BL on January 17, 2017, 07:39:31 PM
I was really only suggesting the 400 because of the teflon and the silver plated mesh. It's much easier to work with than 58 when soldering with a big iron, which is usually needed, at least the way I do it. The 58 will melt in a heart beat. That's all.

The RG-400 is a better option for sure.  If you can get your hands on it easily, use it! :)


Title: RE: Which amp to start with?
Post by: W8JX on January 18, 2017, 04:17:34 AM

Having checked the specifications, the RG-58 Chris has ordered is rated to 1400 Volts - well more than enough for a Kw into a decent SWR load.


The voltage rating limiting factor only for very high SWR not on a reasonably resonant load. (1 kw is just a little over 200v in a 50 ohm load) Conductor/cable size and its attenuation is limit here. I like smaller cables but 58 is too small for a balun that will see 1 kw or more high duty cycles. The core may be slow to heat because of its mass but it will heat over time and get quite warm and cable even warmer over time and cool very slowly due to limited surface are for its thermal mass. What 58 can safely handle long term in a single run vs in a tight coil is a different matter completely.


Title: RE: Which amp to start with?
Post by: VK3BL on January 18, 2017, 04:42:30 PM
The voltage rating limiting factor only for very high SWR not on a reasonably resonant load. (1 kw is just a little over 200v in a 50 ohm load) Conductor/cable size and its attenuation is limit here. I like smaller cables but 58 is too small for a balun that will see 1 kw or more high duty cycles. The core may be slow to heat because of its mass but it will heat over time and get quite warm and cable even warmer over time and cool very slowly due to limited surface are for its thermal mass. What 58 can safely handle long term in a single run vs in a tight coil is a different matter completely.

Agreed.

The difference is however, I have actually tested this exact configuration. 

As previously stated, I ran 1.2Kw through the balun into a Bird 8201, and the only things to get hot enough to warrant ending the test were my AL-572 & Bird 8201.

Bear in mind the Balun in question is a common mode choke NOT a transformer.  There is only ever core heating IF the balun has to choke off excessive common mode current. 

On the off chance you do blow up a core or melt the coax, its an indication that your antenna system is not suited to the band you wish to use, not an indication of the balun not handling enough power.

If you don't believe me, try for yourself.  FT240-43 cores are cheap, and RG-58 even cheaper.


Title: RE: Which amp to start with?
Post by: KH6AQ on January 19, 2017, 11:52:27 AM
Does the AL-811 push the tubes beyond their limits?

The amp is rated for 500 watts OOK CW with an efficiency of 65%. During CW keying the total average plate dissipation is 135 watts for 45 watts per tube. The CCS rating of the plate is 45 watts. The ICAS is 65 watts.

The average plate current and average grid current are within the tube CCS ratings. The parameter that is high is the plate voltage. It is rated for 1250V CCS and 1500V ICAS. According to W8JI the tube cooling is adequate and the envelope and seal temperatures are ok.

Looking at the RCA datasheet we see that for class AB2 SSB the AL-811 output of 200 watts per tube is below the is midway between the maximum CCS rating of 165 watts and the ICAS rating of 235 watts.  

http://www.g8wrb.org/data///RCA/811.pdf

How about the RTTy rating of each amp. AL-811 is 400 watts while the AL-80B is 500 watts.

How about eham reviews? The AL-811, and the AL-80B both score 4.5.

I'm thinking that most of the 811A failures are due to tune up abuse. That is, not adhering to the 5 second ON, 15 second cooling period or not using a pecker or CW dits for tuning.


Title: RE: Which amp to start with?
Post by: KB1SNJ on January 19, 2017, 01:51:41 PM
While I wait for the toroids and coax to try and stop the RF in the house, I experimented on the computer monitor by unplugging the headphones, and hdmi. Turns out it was the HDMI cable which travels up to the ceiling and back down the other side, about 35ft.

Today I was making digital contacts on 20m, and when transmitting, the monitor was shimmering badly.

Hopefully setting up a choke or chokes can put the RF outside the house. Although since the bottom of the antenna is only 10ft away anway. But we'll see, and I'll post results.


Title: RE: Which amp to start with?
Post by: KK4YDR on January 19, 2017, 02:36:42 PM
two things come to mind when you mention RFI on your computer monitor.

1. poorly matched antenna or a poor antenna
2. and/or using a vertical antenna with no common mode choke. Even if it is a perfect 36 ohm match (unique to verticals yes) you still must use common mode choke becuase the coax braided outer shield is going to act just like any other radial in the vericals ground plane system.


Title: RE: Which amp to start with?
Post by: W6GRD on January 19, 2017, 02:47:42 PM
my house is roughly 20x30 and against the boundary on 2 sides, so I can run a radial around the perimeter like a loop, what would that do for RF coming back as well as a pattern if it were under a vertical roughly in the middle above the house?  and does the vertical have to extend down to the ground?  another question is that my property is 40ft wide and faces east west the long way. I suppose I could erect poles at each side maybe at the back lot corners,  and that would span 40ft with the broadside facing east-west.  I wonder what min height would be needed? (I will look that up). what would it take to work 160-6 on a horizontal wire/dipole that spans only 40ft?

Chris,

I have similar space challenges. I also at one point had an end fed. At 100 watts things were ok. At 300 watts I too started tripping GFCIs and a field strength meter confirmed a lot of RF in the shack. I changed things up to use a 20/40 parallel (fan) dipole in a lateral "L" configuration. This was a great improvement not only in signal but in cleaning up RFI. I can run 600 watts now with out a problem. Sure, this only covers 20 and 40 meters but I have used a coil shortened version for 75m amd adding shorter legs for other bands is not impacted by lot space.
Here's a graphic of how I ended up fitting a dipole. Maybe it's an option for your lot.
(https://s3.amazonaws.com/files.qrz.com/d/w6grd/Antenna_Lot_10_7_2016.JPG)


Title: RE: Which amp to start with?
Post by: VK3BL on January 19, 2017, 03:12:55 PM
Does the AL-811 push the tubes beyond their limits?

I'm thinking that most of the 811A failures are due to tune up abuse. That is, not adhering to the 5 second ON, 15 second cooling period or not using a pecker or CW dits for tuning.

In my experience it is not.  I've got 811As lying all over the shack that are in perfect physical condition - you'd think they were NOS, but have no output left.

I can't put my finger on the exact failure method, other than there being no emission left in the cathodes.  Perhaps this is due to outgassing of other elements / cathode poisoning, or perhaps just the fact the tubes ARE pushed pretty damn hard in the AL-811.  The bias / idle current alone takes up most of the CCS dissipation of an 811A.  And yes, I've even tried NOS RCAs.  Contrary to what has been written elsewhere, they are not an '80 watt' tube, or significantly longer lived when used in an AL-811.

A set will only last somewhere between 500-1500 hours SSB service in an AL-811; I have no doubt in my mind that a 3-500ZG will last appreciably longer in an AL-80B.

811A tubes are cheap, but if you're a big amp user removing the 18 screws to change them will drive you nuts in the end.


Title: RE: Which amp to start with?
Post by: VK3BL on January 19, 2017, 03:15:43 PM
While I wait for the toroids and coax to try and stop the RF in the house, I experimented on the computer monitor by unplugging the headphones, and hdmi. Turns out it was the HDMI cable which travels up to the ceiling and back down the other side, about 35ft.

Today I was making digital contacts on 20m, and when transmitting, the monitor was shimmering badly.

Hopefully setting up a choke or chokes can put the RF outside the house. Although since the bottom of the antenna is only 10ft away anway. But we'll see, and I'll post results.

Chuck some ferrite cores around the HDMI cable, or better yet, figure out a way of not having such a long one.


Title: RE: Which amp to start with?
Post by: KB1SNJ on January 19, 2017, 03:37:33 PM
The cable ends are pretty big and I dont know what kind of toroids to use, or how many times to bring the hdmi through (and its barely long enough anyway). No way to go shorter either.

BTW, as to toroids, I dont think they have ever worked for me except once in a mobile installation. But hopefully using them as a choke at the feedpoint can help, and beyond that maybe on something like the monitor if i can figure out what one to get. It would have to be at both ends, monitor and pc,  as well because for all I know, the RF is going into the video controller at the pc and making the distortions there.

Grover thanks for the diagram! So thats a 34ft x2 single wire dipole center fed?  I would need to match on 80m (and love it if i could try 160m, even if inefficient). what kind of 20ft poles did you use and what is the pole at your shack for?

Chuck some ferrite cores around the HDMI cable, or better yet, figure out a way of not having such a long one.


Title: RE: Which amp to start with?
Post by: KB1SNJ on January 19, 2017, 04:09:58 PM
Hey I just realized that a Field Strength Meter may be helpful, but are the ones at the "affordable" end of the spectrum accurate and useful for this? What kind do you use? I like to quantify things.



Chris,

I have similar space challenges. I also at one point had an end fed. At 100 watts things were ok. At 300 watts I too started tripping GFCIs and a field strength meter confirmed a lot of RF in the shack. I changed things up to use a 20/40 parallel (fan) dipole in a lateral "L" configuration. This was a great improvement not only in signal but in cleaning up RFI. I can run 600 watts now with out a problem. Sure, this only covers 20 and 40 meters but I have used a coil shortened version for 75m amd adding shorter legs for other bands is not impacted by lot space.
Here's a graphic of how I ended up fitting a dipole. Maybe it's an option for your lot.

[/quote]


Title: RE: Which amp to start with?
Post by: W6GRD on January 19, 2017, 04:11:00 PM

Grover thanks for the diagram! So thats a 34ft x2 single wire dipole center fed?  I would need to match on 80m (and love it if i could try 160m, even if inefficient). what kind of 20ft poles did you use and what is the pole at your shack for?

Correct, two ~34 ft 14 gauge wires for 40m, center fed with a 1:1 current balun.
The masts/poles are 2 sections each of 10 ft fence post top rail attached to the corner posts of a fence that borders my property. The center mast has an addition 5 ft of PVC on top for isolation and additional height.

The pole depicted at the shack is attached to a vent pipe above the house and has been used for various vertical and wire antennas. It changes frequentlyas I test various options but here is the current configuration. The 75m requires I use a tuner, mostly due to the extreme angle of the horizontal V and droop.
(https://s3.amazonaws.com/files.qrz.com/d/w6grd/Antenna_Lot_12_2016_PNG.jpg)


Title: RE: Which amp to start with?
Post by: W8JX on January 19, 2017, 05:11:04 PM
How about the RTTy rating of each amp. AL-811 is 400 watts while the AL-80B is 500 watts.

Guess again. Both those exceed tube ratings key down. I would say 300 watts for AL 811 and 400 tops for AL811H  RTTY. THey aree light duty amps at best.

I'm thinking that most of the 811A failures are due to tune up abuse. That is, not adhering to the 5 second ON, 15 second cooling period or not using a pecker or CW dits for tuning.

They eat tubes because they are over rated and greatly exceed tube ratings plain and simply. Except for maybe sweep tube amps of 30 to 40 years ago, no amp built exceeded its tubes rating like AL811 amps. A old SB200 can make 600 watts without exceeding tube ratings. To put it into perspective, a 50 year old SB200 design has over twice the safe contentious dissipation of a AL811 "rated" at 600 watts. I SB200 also has nearly twice the dissipation of a AL811H. A AL80B has over 2.5 times the dissipation of a AL811H. I would not waste money on a AL811.


Title: RE: Which amp to start with?
Post by: KB1SNJ on January 19, 2017, 05:19:51 PM
I think I will rule out the 811 based on this feedback. Once I get the antenna sorted out and add an amp and heavy tuner, I'll likely make mistakes. Having robust unit will be probably cost effective for me.

The 80B really seems the ticket if I can find one used. It uses one 3-500Z available for about $200 if needed.

I also like the SB200 idea but it wont go down to 160, which probably doesnt matter all that much to me.  It uses two 572B tubes. I looked for general cost on those, since they are the most replaceable part, and RF Parts has them for $160/pair.

As an aside, they also posted this info:
EXISTING 572B CURRENTLY ON THE MARKET
Since 1994, the Shuguang factory in China has produced the 572B, ceasing production in 2013.
 The Shuguang tubes we see available on eBay are believed to be the returns from RF PARTS and Ameritron that did not meet spec




Title: RE: Which amp to start with?
Post by: W6GRD on January 19, 2017, 05:44:53 PM
I too have been in your seat. The AL-80B is by far the fan favorite as far as I can tell. I was considering one but then I had a chance to buy a well taken care of SB-200 from a local at a good price ($400) and I knew it worked. It had all the common Harbach upgrades and Svetlana tubes. I also was aware of the fact that if I was going to go to the 1.5K arena there was additional work and attention to detail (and cost). The ~600 watt arena suits my working situation. I later moved to an ALS-600 for other reasons, but what I did learn is that I am happy at ~600 watts. I do covet an SB-220. I'd like to find one that need a total refurbish and rebuild it myself. If I had to do it again based on wattage per dollar+warranty+support, AL-80B, SB-200 (I admit I got lucky/good deal) and then ??? We shall see. I do like the ALS-600 very much and use it daily. I can recommend that as well.

The new generation 572b tubes from RF Parts have been getting good reviews (see another thread in this section). I found the the SB-200 is an easy 500-600 watts and simple to tune once I learned the nuances.


Title: RE: Which amp to start with?
Post by: W8JX on January 19, 2017, 05:52:10 PM
The new generation 572b tubes from RF Parts have been getting good reviews (see another thread in this section). I found the the SB-200 is an easy 500-600 watts and simple to tune once I learned the nuances.

A used SB200 in good order is far more rugged than any AL811 series amp new. I doubt you could build a SB 200 quality amp today for sale for less than a grand. It was a well built amp.


Title: RE: Which amp to start with?
Post by: VK3BL on January 19, 2017, 07:48:57 PM
As an aside, they also posted this info:
EXISTING 572B CURRENTLY ON THE MARKET
Since 1994, the Shuguang factory in China has produced the 572B, ceasing production in 2013.
 The Shuguang tubes we see available on eBay are believed to be the returns from RF PARTS and Ameritron that did not meet spec


Thats complete unfounded bullshit.

The 572Bs currently available *everywhere* are current production Shu Guang.  You can easily verify this as they have a new plate design with more mass.

That said, I would chose an AL-80B (or AL-572) over an SB-200.  Mainly because the AL-80B is in production and full manufacturer support is available.  It is a modern design, and works properly with modern transceivers.

The AL-572 amp is the same as an AL-80B, but is rated at 1200 watts CW using 4x 572Bs.


Title: RE: Which amp to start with?
Post by: W8JX on January 20, 2017, 03:30:58 AM
That said, I would chose an AL-80B (or AL-572) over an SB-200.  Mainly because the AL-80B is in production and full manufacturer support is available.  It is a modern design, and works properly with modern transceivers.

Most SB200's in use today have had a soft key mod to use with modern rigs and if not it is easy to add mod. As far as in production vs not is not as important as quality and if SB200's were not a good quality and reliable unit they would not still be in use 40 years later. I have a stock SB200 that I use as a backup that is still very tight and tunes nicely. I have parts to upgrade power supply and add soft key when I get around to it.


Title: RE: Which amp to start with?
Post by: K4RVN on January 20, 2017, 08:20:26 AM
Here is a great way to install a dipole on a small lot and not very high required. Also you may want to consider the super NVIS
antenna which is only 7 feet above ground. I have used both of these with good results.
http://www.comportco.com/~w5alt/antennas/notes/ant-notes.php?pg=16

http://www.hamuniverse.com/supernvis.html
Use a dipole about 30 ft each side of the insulator or bend the ends to add length of the wire for your desired freq. I have worked Hawaii with this antenna although it is a cloud warmer in normal propagation. Really great for rag chews of a few hundred miles.
I have owned the AL811 and now the AL80B Ameritron. I would suggest a used or new AL80B for your amp as it is a long term solution and a great amp, good value.

Frank


Title: RE: Which amp to start with?
Post by: VK3BL on January 20, 2017, 06:16:41 PM
That said, I would chose an AL-80B (or AL-572) over an SB-200.  Mainly because the AL-80B is in production and full manufacturer support is available.  It is a modern design, and works properly with modern transceivers.

Most SB200's in use today have had a soft key mod to use with modern rigs and if not it is easy to add mod. As far as in production vs not is not as important as quality and if SB200's were not a good quality and reliable unit they would not still be in use 40 years later. I have a stock SB200 that I use as a backup that is still very tight and tunes nicely. I have parts to upgrade power supply and add soft key when I get around to it.

I recommend new amp users buy current production models mainly so that any oppsie moments can be sorted out with the minimum of fuss - there is always the factory to send the amp back to if you can't repair it yourself.

We don't see many Heathkits in VK.  A SB-1000 came up for sale last year but I didn't have the money at the time to buy it.  Really like the look of the SB-1000.


Title: RE: Which amp to start with?
Post by: W8JX on January 20, 2017, 06:23:39 PM
I recommend new amp users buy current production models mainly so that any oppsie moments can be sorted out with the minimum of fuss - there is always the factory to send the amp back to if you can't repair it yourself.

Well new and cheaply built (like AL811 series) is more likely to need repair than old and properly built.


Title: RE: Which amp to start with?
Post by: VK3BL on January 20, 2017, 06:30:16 PM
I recommend new amp users buy current production models mainly so that any oppsie moments can be sorted out with the minimum of fuss - there is always the factory to send the amp back to if you can't repair it yourself.

Well new and cheaply built (like AL811 series) is more likely to need repair than old and properly built.

Yes, a good second hand AL-80B is likely the best option for a beginner.


Title: RE: Which amp to start with?
Post by: W8JX on January 20, 2017, 06:34:52 PM
I recommend new amp users buy current production models mainly so that any oppsie moments can be sorted out with the minimum of fuss - there is always the factory to send the amp back to if you can't repair it yourself.

Well new and cheaply built (like AL811 series) is more likely to need repair than old and properly built.

Yes, a good second hand AL-80B is likely the best option for a beginner.

Maybe not best but close to it.  A SB200 that has been gone throw and freshened is still a good choice for a 500+ watt amp.


Title: RE: Which amp to start with?
Post by: VK3BL on January 20, 2017, 10:16:51 PM
Maybe not best but close to it.  A SB200 that has been gone throw and freshened is still a good choice for a 500+ watt amp.

A single 3-500ZG is better than 2x 572Bs though.


Title: RE: Which amp to start with?
Post by: W8JX on January 21, 2017, 03:39:02 AM
Maybe not best but close to it.  A SB200 that has been gone throw and freshened is still a good choice for a 500+ watt amp.
A single 3-500ZG is better than 2x 572Bs though.

Not always. Good 572's are just as rugged just less power potenail and a pair is cheaper than a single 3-500 too. A 3-500z is a good tube it is just not really cooled properly in many amps using it to fully exploit its ratings. Strangely Ameritron cools it properly in AL82 but not in AL80


Title: RE: Which amp to start with?
Post by: KB1SNJ on January 21, 2017, 02:02:30 PM
UPDATE" re: the choke, didnt do a thing.

Made choke #1 per this chart  http://www.karinya.net/g3txq/chokes/ (http://www.karinya.net/g3txq/chokes/) and keyed up on 80M, jammed my monitor hard as always, knocked it off line. Also had the buzzing in the mixer/headphones.

The picture shown is just outside the window. maybe 8ft away from the actual radio gear.

Not sure what to conclude. maybe the RF is from the antenna itself and there is no CM coming back now? Not sure how to tell the difference.

(https://c1.staticflickr.com/1/356/31634983443_1ae4d1663b_k.jpg) (https://flic.kr/p/Qctyr2)20170121_164734 (https://flic.kr/p/Qctyr2) by Chris P (https://www.flickr.com/photos/143794395@N08/), on Flickr


Title: RE: Which amp to start with?
Post by: VK3BL on January 21, 2017, 05:35:16 PM
On the plus side, the choke looks well made :)

I'd suggest the 'ground' side of your antenna is woefully inadequate.  You can't use a single thin wire from the antenna ground point to a bunch of radials, you have to connect each and every radial to the antenna (in this case balun) base.

I'd attach another 6-7 wires.  They don't have to be massively long or anything, just as long as you can make them, and rest them on whatever ground you have.

Then try again :)

Edit: also what is that loop of grey cable?  Get that sitting on the ground, it is probably acting as an antenna and bringing RF back into the shack.


Title: RE: Which amp to start with?
Post by: VK3BL on January 21, 2017, 05:40:09 PM
Not always. Good 572's are just as rugged just less power potenail and a pair is cheaper than a single 3-500 too. A 3-500z is a good tube it is just not really cooled properly in many amps using it to fully exploit its ratings. Strangely Ameritron cools it properly in AL82 but not in AL80

I hope you're right.  I enjoy my AL-572 very much, but if it chews through tubes even half as quick as my AL-811 did I'll be chasing an AL-80B pronto.

Truth be told I don't push the AL-572 anywhere near as hard as I did the AL-811.  Our power limit here is only 400 Watts PEP.


Title: RE: Which amp to start with?
Post by: VK3BL on January 21, 2017, 05:43:14 PM
Also thinking about it Chris:

Try this:

1) Bury / place on ground any excess feed line.
2) Connect the feed line to your 1:1 Balun
3) Connect your radials to the "cold" antenna side of the 1:1 balun, making sure the feed line is LOWER than the radials.  Run many radials from the 1:1 balun antenna side.

4) Connect your antenna element to the "hot" side of the 1:1 Balun.


See how the system works like that.


Title: RE: Which amp to start with?
Post by: KB1SNJ on January 21, 2017, 06:56:40 PM
thanks for the words, the coiled gray coax is excess feedline, there's a little more below as well.  The "alley" between the house and fence has a radial on the ground going away from the camera about 20ft, there is about a 10ft radial behind the camera before it stops at the rear fence. I can only go to the left of the camera as a 3rd direction and that goes 40ft. (Theres a diagram of the property and house back a couple pages).

The rear of the property is 40ft wide and I can probably put is support post at each corner sticking up 15ft or so. That would put the broadside toward west which I need.

several have made small lot antenna suggestions. It will be a hassle but putting up some poles and trying different things may be the only answer.

I really thought a 50ft vertical wire would have great potential. It does work, but I guess not so much.


Title: RE: Which amp to start with?
Post by: VK3BL on January 22, 2017, 04:05:30 AM
I really thought a 50ft vertical wire would have great potential. It does work, but I guess not so much.

It might very well do with a bit of tweaking.  50ft might be a bit on the long side - a 43ft element may work a little better depending on frequency etc.  I note 43ft verticals are a popular length.

I would say if you dumped the excess feed line on the ground rather than up near the current maximum of your radiator (the feed point) you'd do a lot better.  Sitting where it is it is just asking to soak up RF, and its AFTER the current choke too so its going to get RF hot.

In fact, I just recently had my audio go terrible because my 2M feed line had been wrapped around my HF feed line a few times, and was bringing RF into the shack.

Feed lines - you have to be careful with them! :)



Title: RE: Which amp to start with?
Post by: W8JX on January 22, 2017, 04:14:11 AM
Not always. Good 572's are just as rugged just less power potenail and a pair is cheaper than a single 3-500 too. A 3-500z is a good tube it is just not really cooled properly in many amps using it to fully exploit its ratings. Strangely Ameritron cools it properly in AL82 but not in AL80

I hope you're right.  I enjoy my AL-572 very much, but if it chews through tubes even half as quick as my AL-811 did I'll be chasing an AL-80B pronto.

Truth be told I don't push the AL-572 anywhere near as hard as I did the AL-811.  Our power limit here is only 400 Watts PEP.

I think a weakness in AL-572 is cooling. Ameritron tends to focus more on quiet than cooling on its amps in that class. My Dentron has a very aggressive/noisy fan that I reversed to suck air out over 20 years ago and it keeps case cool to touch even after hours of use. (before I reversed it amp got pretty hot to touch after usage)


Title: RE: Which amp to start with?
Post by: W8JX on January 22, 2017, 04:18:15 AM
It might very well do with a bit of tweaking.  50ft might be a bit on the long side - a 43ft element may work a little better depending on frequency etc.  I note 43ft verticals are a popular length.

If you run 80 and 160 the extra length can help a bit but if you run mostly 40 and higher, a 33 footer will play better.


Title: RE: Which amp to start with?
Post by: AC2RY on January 22, 2017, 01:33:36 PM
UPDATE" re: the choke, didnt do a thing.

Made choke #1 per this chart  http://www.karinya.net/g3txq/chokes/ (http://www.karinya.net/g3txq/chokes/) and keyed up on 80M, jammed my monitor hard as always, knocked it off line. Also had the buzzing in the mixer/headphones.

The picture shown is just outside the window. maybe 8ft away from the actual radio gear.

Not sure what to conclude. maybe the RF is from the antenna itself and there is no CM coming back now? Not sure how to tell the difference.

(https://c1.staticflickr.com/1/356/31634983443_1ae4d1663b_k.jpg) (https://flic.kr/p/Qctyr2)20170121_164734 (https://flic.kr/p/Qctyr2) by Chris P (https://www.flickr.com/photos/143794395@N08/), on Flickr

You didn't mention is you have any tuner. With non-resonant antennas like yours you must have a wide band tuner. Do you have antenna analyzer? What is your SWR range on bands you plan to use? Considering that you cannot have enough radials, it is almost a must to have tuner at antenna feed point. Another problem is that antenna is too close to house. This is not only problem on transmit, but receive too. What is your average noise level on 20 and 40m? As was mentioned above, amplifier is the last thing to put in. Even if you get an amplifier, you will need a wide band tuner to use it with most multiband antennas. And this tuner can be expensive for 1000W power.



Title: RE: Which amp to start with?
Post by: KB1SNJ on January 22, 2017, 01:39:21 PM
My ftdx3000 internal tuner has matched 80 40 20 on this antenna, and the top of 160. Haven't tried the others but I do also have a mfj automatic tuner and the control cable and that tuner has a wider range of capability just haven't needed it yet.

I do realize now that I will need a new tuner capable of handling the power of an amplifier if and when I add an amplifier.

As to noise floor questions I'm not at home to check that right now I'm at work but the receive performance seems very good.

However I absolutely cannot wait to try an antenna and actually have it work well on most of the Bands, just a matter of deciding which approach to put the time and effort into first.


Title: RE: Which amp to start with?
Post by: KB1SNJ on January 22, 2017, 01:57:32 PM
Some of the things I'm starting to consider all at once regarding an antenna is efficiency, directionality, and takeoff angle.

It seems like even if an antenna can be impedance matched, that doesn't mean the full power of the transmitter is going out to the airwaves, and what is going out may not be going in an Optimum Direction.

I downloaded eznec demo but got completely lost when trying to use it, not very intuitive, so I guess I'll have to read some!


Title: RE: Which amp to start with?
Post by: AC2RY on January 22, 2017, 02:52:52 PM
My ftdx3000 internal tuner has matched 80 40 20 on this antenna, and the top of 160. Haven't tried the others but I do also have a mfj automatic tuner and the control cable and that tuner has a wider range of capability just haven't needed it yet.

I do realize now that I will need a new tuner capable of handling the power of an amplifier if and when I add an amplifier.

As to noise floor questions I'm not at home to check that right now I'm at work but the receive performance seems very good.

However I absolutely cannot wait to try an antenna and actually have it work well on most of the Bands, just a matter of deciding which approach to put the time and effort into first.

I would start with getting antenna analyzer. Without it you are just shooting in the dark. When yu build new antenna and make sure that impedance is reasonable both at feed point and at the shack side of coax line, then you can start playing with more power. With compromised antennas you tuner in your transciever does not do much to improve power transfer into antenna. You should have ZERO RF reflected back into the shack BEFORE even considering any power over 100W.


Title: RE: Which amp to start with?
Post by: W8JX on January 22, 2017, 03:47:40 PM
It might very well do with a bit of tweaking.  50ft might be a bit on the long side - a 43ft element may work a little better depending on frequency etc.  I note 43ft verticals are a popular length.

If you work 40m and higher mostly a 33 footer will do better. A 43 will do a bit better on 80 and 160 but not 40 and at 20 and above the wave angle on 43 footer starting getting to much higher angle not favorable for DX. 50 footer gets higher yet and a bit sooner.


Title: RE: Which amp to start with?
Post by: VK3BL on January 22, 2017, 06:54:12 PM
It might very well do with a bit of tweaking.  50ft might be a bit on the long side - a 43ft element may work a little better depending on frequency etc.  I note 43ft verticals are a popular length.

If you work 40m and higher mostly a 33 footer will do better. A 43 will do a bit better on 80 and 160 but not 40 and at 20 and above the wave angle on 43 footer starting getting to much higher angle not favorable for DX. 50 footer gets higher yet and a bit sooner.

Yeah good advice - admittedly I didn't bother running any NEC calcs or doing much research.

I'm still keen to find out if Chris has moved that feed line which looks like a loop antenna yet :)


Title: RE: Which amp to start with?
Post by: KB1SNJ on January 22, 2017, 07:18:37 PM
 no I have not moved to feed line yet but I'm going to
Yes I have an mfj 223 antenna analyzer and I will post a picture of the result in fact if I can remember I'll do it before I tidy up the feed line and after


Title: RE: Which amp to start with?
Post by: KH6AQ on January 23, 2017, 04:10:43 AM

According to this article in which the author analyzes the 811A tube the import tubes do have "the same 65-watt long-term dissipation" as the original 811A. Therefore, the AL-811 amp does not push the tube anywhere near it's ICAS dissipation rating during CW at 500 watts. The tube anode dissipation is 45 watts and is within the CCS rating.

https://www.w8ji.com/811a_tube.htm

The author points out that "the new import anode greatly reduces shorter term dissipation capability." This should not matter during normal operation when the anode dissipation is 45 watts average, but could matter during careless tuning. And looking at the eham reviews of the AL-811 and AL-811H we see reports of early arcing failures. This could be due to poor tube manufacturing creating a gassy or dirty tube, or it could be due to careless tuning liberating gas from the anode. Two other issues that will increase anode voltage are under-loading and exciter RF power spiking.

We don't see many reports of normal end-of-life, which is the loss of cathode emission.

So, I see no evidence that reducing RF output power will prolong the life of the 811A tubes in this application. The evidence suggests that five things may lead to arcing:

Poor tube processing leading to low voltage holdoff
Prolonged tuning causing anode outgassing
Prolonged tuning creating holes in the anode (arc nucleation sites)
Under-loading the output circuit
Exciter RF spiking


And with three tubes in parallel the probability of an early-life failure, or a steady-state failure, is tripled.

Looking at eham reviews of the AL-80B amp I do not see any arcing failures (I did not look at every review) and it does appear to be the more reliable amp.




Title: RE: Which amp to start with?
Post by: W8JX on January 23, 2017, 04:34:29 AM

According to this article in which the author analyzes the 811A tube the import tubes do have "the same 65-watt long-term dissipation" as the original 811A. Therefore, the AL-811 amp does not push the tube anywhere near it's ICAS dissipation rating during CW at 500 watts. The tube anode dissipation is 45 watts and is within the CCS rating.


What math are you using?  45 x 3 equals 135 watts. 500 out means at least 750 watts input over 250 watts dissipation which is nearly twice the safe continuous dissipation on the tubes and and about 30% above the short term 65 watts ICAS rating of tube. Plus what you are leaving out is that the bias setting on amp is such that keydown standby (between dots and dashes) you are nearly at 45 watts per tube idle current so amp is in ICAS rating as soon as you depress CW key or talk. (many fail to realize this and figure key up tube rests but it does not and ICAS ratings are based on short terms loads and cool down times on zero plate current not at standby current) If you want reasonable tube life use 400 max for CW and 300 for RTTY. The AL811 series is the most over rated amp ever built.


Title: RE: Which amp to start with?
Post by: KB1SNJ on January 23, 2017, 08:38:32 AM
(https://c1.staticflickr.com/1/643/32443303856_354b9616eb_n.jpg) (https://flic.kr/p/RqUpVS)20170123_105353 FULL (https://flic.kr/p/RqUpVS) by Chris P (https://www.flickr.com/photos/143794395@N08/), on Flickr

80M
(https://c1.staticflickr.com/1/309/32483888855_f9655170da_n.jpg) (https://flic.kr/p/Ruuqre)80M 20170123_105700 (https://flic.kr/p/Ruuqre) by Chris P (https://www.flickr.com/photos/143794395@N08/), on Flickr

40M
(https://c1.staticflickr.com/1/417/32332370352_fcb8baa31f_n.jpg) (https://flic.kr/p/Rg6Rgf)50ft vert 40m band (https://flic.kr/p/Rg6Rgf) by Chris P (https://www.flickr.com/photos/143794395@N08/), on Flickr

20M
(https://c1.staticflickr.com/1/720/32332461532_2501fa5552_n.jpg) (https://flic.kr/p/Rg7jnj)20170123_105815 20m (https://flic.kr/p/Rg7jnj) by Chris P (https://www.flickr.com/photos/143794395@N08/), on Flickr

10M
(https://c1.staticflickr.com/1/758/32332465932_48789d59e4_n.jpg) (https://flic.kr/p/Rg7kFb)20170123_105936 50ft vert 10m (https://flic.kr/p/Rg7kFb) by Chris P (https://www.flickr.com/photos/143794395@N08/), on Flickr


Title: RE: Which amp to start with?
Post by: K6AER on January 23, 2017, 09:25:16 AM

According to this article in which the author analyzes the 811A tube the import tubes do have "the same 65-watt long-term dissipation" as the original 811A. Therefore, the AL-811 amp does not push the tube anywhere near it's ICAS dissipation rating during CW at 500 watts. The tube anode dissipation is 45 watts and is within the CCS rating.


What math are you using?  45 x 3 equals 135 watts. 500 out means at least 750 watts input over 250 watts dissipation which is nearly twice the safe continuous dissipation on the tubes and and about 30% above the short term 65 watts ICAS rating of tube. Plus what you are leaving out is that the bias setting on amp is such that keydown standby (between dots and dashes) you are nearly at 45 watts per tube idle current so amp is in ICAS rating as soon as you depress CW key or talk. (many fail to realize this and figure key up tube rests but it does not and ICAS ratings are based on short terms loads and cool down times on zero plate current not at standby current) If you want reasonable tube life use 400 max for CW and 300 for RTTY. The AL811 series is the most over rated amp ever built.

I did not see the duty cycle mentioned but as John had mentioned with 500 watts out in CW (50% duty cycle) with typical Class AB1 efficiency of 55%, equals 450 watts of tube dissipation. The tubes will not last long.


Title: RE: Which amp to start with?
Post by: W8JX on January 23, 2017, 10:19:29 AM
I did not see the duty cycle mentioned but as John had mentioned with 500 watts out in CW (50% duty cycle) with typical Class AB1 efficiency of 55%, equals 450 watts of tube dissipation. The tubes will not last long.

Even if you could get 60% efficiency you still have over 350 watts to loose or roughly 120 watts per tube on tubes rated at only 45 watts continuous.  The 811 tube is the most abused and over used tube out there yet some think they are a great amp tube simply because they do not know any better or have trouble with math..


Title: RE: Which amp to start with?
Post by: AC2RY on January 23, 2017, 11:25:39 AM
(https://c1.staticflickr.com/1/643/32443303856_354b9616eb_n.jpg) (https://flic.kr/p/RqUpVS)20170123_105353 FULL (https://flic.kr/p/RqUpVS) by Chris P (https://www.flickr.com/photos/143794395@N08/), on Flickr

80M
(https://c1.staticflickr.com/1/309/32483888855_f9655170da_n.jpg) (https://flic.kr/p/Ruuqre)80M 20170123_105700 (https://flic.kr/p/Ruuqre) by Chris P (https://www.flickr.com/photos/143794395@N08/), on Flickr

40M
(https://c1.staticflickr.com/1/417/32332370352_fcb8baa31f_n.jpg) (https://flic.kr/p/Rg6Rgf)50ft vert 40m band (https://flic.kr/p/Rg6Rgf) by Chris P (https://www.flickr.com/photos/143794395@N08/), on Flickr

20M
(https://c1.staticflickr.com/1/720/32332461532_2501fa5552_n.jpg) (https://flic.kr/p/Rg7jnj)20170123_105815 20m (https://flic.kr/p/Rg7jnj) by Chris P (https://www.flickr.com/photos/143794395@N08/), on Flickr

10M
(https://c1.staticflickr.com/1/758/32332465932_48789d59e4_n.jpg) (https://flic.kr/p/Rg7kFb)20170123_105936 50ft vert 10m (https://flic.kr/p/Rg7kFb) by Chris P (https://www.flickr.com/photos/143794395@N08/), on Flickr


Well, for me this means that antenna cannot be used on any band than maybe 12M. Low SWR between bands only means very high loss somewhere. Internal tuner in transciever is only useful when SWR is below 2.5 (or even 2.0). This is not a surprise no one hears you. In conditions like yours, I would use remote wide band tuner first. Look at one that is made by LDG. RT-600 could be a good match (and will work with some amplifiers too). Yaesu itself has FC-40, though it is limited to 100W. But 100W with proper tuner should allow you to work all over continental US, Canada, Central America and often Western Europe or South America. You won't break a pileup, but will be heard over there. If you still want 1KW radiated, install proper (it means resonance antenna) first. From the layout of your house you have enough space on the other side for real vertical or GP. There you will be able to send your desired KW of RF energy.



Title: RE: Which amp to start with?
Post by: W8JX on January 23, 2017, 11:45:49 AM
Just remember a very poor antenna with poor radiation efficiency can still have a low SWR so low SWR does not guarantee good performance.


Title: RE: Which amp to start with?
Post by: AC2RY on January 23, 2017, 12:06:02 PM
Just remember a very poor antenna with poor radiation efficiency can still have a low SWR so low SWR does not guarantee good performance.

In hes results R value is very high. On lower bands it should be very low.


Title: RE: Which amp to start with?
Post by: KB1SNJ on January 23, 2017, 12:07:04 PM
Thanks for replies. Just throwing in that my radios tuner gets swr below 2:1 usually much below on 80 40 20

I got a contact in WV but was light to him.


Title: RE: Which amp to start with?
Post by: AC2RY on January 23, 2017, 01:50:55 PM
Thanks for replies. Just throwing in that my radios tuner gets swr below 2:1 usually much below on 80 40 20

I got a contact in WV but was light to him.

Forget internal tuner. It will not help with random wire antenna which you have. Get FC-40 (if it works with FTDX). It is designed for cases like yours. GigaParts has a very good price for it. Do not forget to add lightning arrester. I use similar setup (though from ICOM) with great success.


Title: RE: Which amp to start with?
Post by: VK3BL on January 23, 2017, 02:37:44 PM
According to this article in which the author analyzes the 811A tube the import tubes do have "the same 65-watt long-term dissipation" as the original 811A. Therefore, the AL-811 amp does not push the tube anywhere near it's ICAS dissipation rating during CW at 500 watts. The tube anode dissipation is 45 watts and is within the CCS rating.

We don't see many reports of normal end-of-life, which is the loss of cathode emission.

So, I see no evidence that reducing RF output power will prolong the life of the 811A tubes in this application.

In my experience reading about and owning an AL-811, end-of-life due to loss of cathode emission is exceedingly common.

Myself alone used up 3 sets of 811A tubes running digital modes, within a year.  In no cases was there any obvious damage to the tubes anodes etc; they just lost emission.  It did not matter what brand/make of tubes I used (I tried tubes from every major plant, RCA etc). 

The big elephant in the room with the AL-811 series is that the biasing used accounts for ~70% of the rated dissipation.  In a nutshell, the tubes never get a chance to cool down.  As such, I concur that reducing RF power will not significantly prolong the life of 811A tubes.

The truth is the tubes don't last long in that amp, but they are at least cheap.

I'd love to know exactly what causes short life.  It could be a lack of 'reserve' filament emission in 811A tubes, or it could be that the high average temperatures the tubes are subjected to causes outgassing of the elements and poisons the cathode.

The best thing you can do for tube life in an AL-811, is to look through the side grill and do your best to ensure there is as little colour on the anodes as possible.

The AL-811 series of course has many things going for it.  A major one is the huge surplus of tubes still available at good prices, and new ones still in current production.  I have no doubt in my mind that 20 years from now, they will still be making 811A tubes somewhere.


Title: RE: Which amp to start with?
Post by: KB1SNJ on January 23, 2017, 03:20:48 PM
This reply has me a little bit confused because my understanding was that an antenna matcher (tuner) simply provides the radio with the impedance is looking for - even if it is not resonant or its electrical properties are suboptimal.

Since my built-in tuner on the radio can achieve an acceptable SWR, I believe that's all it can do I don't think another tuner can make any greater difference in the antenna efficiency or performance.

Someone please correct me if I am wrong.






Thanks for replies. Just throwing in that my radios tuner gets swr below 2:1 usually much below on 80 40 20

I got a contact in WV but was light to him.

Forget internal tuner. It will not help with random wire antenna which you have. Get FC-40 (if it works with FTDX). It is designed for cases like yours. GigaParts has a very good price for it. Do not forget to add lightning arrester. I use similar setup (though from ICOM) with great success.



Title: RE: Which amp to start with?
Post by: VK3BL on January 23, 2017, 04:08:40 PM
This reply has me a little bit confused because my understanding was that an antenna matcher (tuner) simply provides the radio with the impedance is looking for - even if it is not resonant or its electrical properties are suboptimal.

Since my built-in tuner on the radio can achieve an acceptable SWR, I believe that's all it can do I don't think another tuner can make any greater difference in the antenna efficiency or performance.

Someone please correct me if I am wrong.


The closer your antenna tuner is to your antenna radiating element, the less loss the system will have.

The goal is to keep the SWR as low as possible on coaxial transmission line - it becomes very lossy over SWRs of 3:1.

As previously mentioned, if you're keen on verticals and using an amplifier, a remote tuner like the MFJ 998RT would be a wise investment.

For your station I would recommend 1 of the following:
1) 33-43ft Vertical with as many radials of random length on the ground as possible, with a remote tuner like the MFJ-998RT (1500w tuner)
2) A G5RV or similar, fed with ladder line, choked off using a 1:1 common mode choke with a short length of coax to a tuner in the shack, like a Palstar AT2K or LDG AT-1000 Pro II

Literally anything other than either of the above options is unlikely to meet your goal of performing well with an amplifier.


Title: RE: Which amp to start with?
Post by: W8JX on January 23, 2017, 06:06:28 PM

The goal is to keep the SWR as low as possible on coaxial transmission line - it becomes very lossy over SWRs of 3:1.


This is misleading as it depends on coax size, length of run and frequency in use as additional loss is based of "normal" matched loss. Example, 100 feet of RG 213 on 20m has a loss of about 3/4 of a db when matched and about 1.6 db (or less than 1 db more) with a 5 to 1 SWR. That is not very lossy.  Shorter runs its even less.


Title: RE: Which amp to start with?
Post by: KB1SNJ on January 23, 2017, 06:09:57 PM
One question I asked is that if my built-in tuner can bring the SWR down to 1.5 or so, how could any other tuner do any better?


Title: RE: Which amp to start with?
Post by: VK3BL on January 23, 2017, 06:48:54 PM
One question I asked is that if my built-in tuner can bring the SWR down to 1.5 or so, how could any other tuner do any better?

A couple of posts up mate


Title: RE: Which amp to start with?
Post by: W9IQ on January 24, 2017, 05:16:31 AM
Quote
One question I asked is that if my built-in tuner can bring the SWR down to 1.5 or so, how could any other tuner do any better?

Chris,

Some tuners operate more efficiently (generate less heat / consume less transmitter power). Some tuners handle high voltage better (the higher voltage is due to the SWR). You internal antenna tuner is doing the job for your so I wouldn't be concerned about either of these in your case.

An antenna that exhibits an SWR higher than 1:1 causes additional losses on the coax. By placing a remote tuner right at the antenna, the coax never sees the higher SWR so no additional losses are created in the coax. As W8JX correctly points out though, it is a question of how much loss you can tolerate. In general, the thinner the center conductor of the coax, the higher the frequency, and the longer the coax - or in other words the greater the matched loss, the greater the additional loss due to SWR.

Since you have a nice antennalyzer, you don't need to guess at any of this. If you have the complex impedance or SWR readings for each band taken at the base of the antenna, you can plug these values into a free program like TLDetails (http://www.ac6la.com/TLDetails.zip (http://www.ac6la.com/TLDetails.zip)). Using this program, you can select your transmission line type, enter the length of the transmission line, enter the SWR (or R and X) as measured at the antenna, and it will show you the SWR at the radio end and the losses in your coax. It is a very nicely done, free program that has lots of other features. As interested as you are in experimenting with antennas, I highly recommend you get comfortable with this program.

- Glenn W9IQ



Title: RE: Which amp to start with?
Post by: KB1SNJ on January 24, 2017, 09:01:11 AM
Thanks Glenn that is great help.   :)   I'll check out your link and try to work with it.  Question:  regarding matching at the antenna with a remote tuner, does that in itself reduce RF radiating from the coax?  Is all RF from feedline caused by CM? (I think not).

I took a couple pics of each band, see what feedback they generate here.

(https://c1.staticflickr.com/1/489/32503234325_fe11e62a53_n.jpg) (https://flic.kr/p/RwczaP)20170124_010325_001 (https://flic.kr/p/RwczaP) by Chris P (https://www.flickr.com/photos/143794395@N08/), on Flickr

(https://c1.staticflickr.com/1/688/32462639186_19689736a6_n.jpg) (https://flic.kr/p/RsBvDC)20170124_010312 (https://flic.kr/p/RsBvDC) by Chris P (https://www.flickr.com/photos/143794395@N08/), on Flickr

(https://c1.staticflickr.com/1/587/32462638996_a35a57ff35_n.jpg) (https://flic.kr/p/RsBvAm)20170124_010300 (https://flic.kr/p/RsBvAm) by Chris P (https://www.flickr.com/photos/143794395@N08/), on Flickr

(https://c1.staticflickr.com/1/757/32462639256_0264de2d9d_n.jpg) (https://flic.kr/p/RsBvEQ)20170124_010242 (https://flic.kr/p/RsBvEQ) by Chris P (https://www.flickr.com/photos/143794395@N08/), on Flickr




Title: RE: Which amp to start with?
Post by: W9IQ on January 24, 2017, 09:18:56 AM
Chris,

A tuner at the base (feedpoint) of the antenna will reduce common mode current only to the extent that it may have an internal choking balun. Remember - high SWR does not cause common mode current.

Other than leakage by the feedline which is normally quite small, CMC is the only practical source of feedline radiation (and ingress).

If you do put a tuner at the feedpoint, your nicely constructed choking balun should go on the "input" connection to the tuner before the coax heads back to your shack. The antenna is connected to the "output" of the tuner.

Another poster mentioned that you should move that coil of coax that you have on the pipe by the feedpoint to another location. I agree with that suggestion and I would recommend that you put the coil of excess coax at the spot where your coax enters the house. At the same time, consider forming it into a couple of coiled choking baluns using the coiling suggestions on the web site you referenced for your ferrite choking balun. If you have enough coax, you can make a couple of these optimized for the different bands on which you are operating.

- Glenn W9IQ


Title: RE: Which amp to start with?
Post by: AC2RY on January 24, 2017, 11:56:51 AM
Thanks Glenn that is great help.   :)   I'll check out your link and try to work with it.  Question:  regarding matching at the antenna with a remote tuner, does that in itself reduce RF radiating from the coax?  Is all RF from feedline caused by CM? (I think not).

I took a couple pics of each band, see what feedback they generate here.

(https://c1.staticflickr.com/1/489/32503234325_fe11e62a53_n.jpg) (https://flic.kr/p/RwczaP)20170124_010325_001 (https://flic.kr/p/RwczaP) by Chris P (https://www.flickr.com/photos/143794395@N08/), on Flickr

(https://c1.staticflickr.com/1/688/32462639186_19689736a6_n.jpg) (https://flic.kr/p/RsBvDC)20170124_010312 (https://flic.kr/p/RsBvDC) by Chris P (https://www.flickr.com/photos/143794395@N08/), on Flickr

(https://c1.staticflickr.com/1/587/32462638996_a35a57ff35_n.jpg) (https://flic.kr/p/RsBvAm)20170124_010300 (https://flic.kr/p/RsBvAm) by Chris P (https://www.flickr.com/photos/143794395@N08/), on Flickr

(https://c1.staticflickr.com/1/757/32462639256_0264de2d9d_n.jpg) (https://flic.kr/p/RsBvEQ)20170124_010242 (https://flic.kr/p/RsBvEQ) by Chris P (https://www.flickr.com/photos/143794395@N08/), on Flickr




I feel you are making a mistake somewhere. You need to consider coax feed line and antenna separately. On one side, you need to make sure that coax is all good. For that, connect resistor of 450 ohms to output terminals of your balun instead of antenna wires. Then use analyzer to check how it all looks like from your shack. You should have SWR below 1.2 and very small X value. If it is not the case, then problem is with coax line or balun. When this is cleared, connect wires back to balun and now use analyzer to measure antenna impedance at input of balun. That will show you how antenna really works at different frequencies.

Regarding remote tuner. The goal is to transform antenna impedance to something close to 50 ohms with low X value. Tuner (or rather coupler - it does exactly that function) compensates antenna capacitance or inductance and transforms impedance. Proper tuner can transform impedance from few ohms to several Kohms with reasonably low loss. Antenna along with tuner become resonant at frequency you want to operate. This is exactly why remote tuner is a must when antenna is not resonant at or near transmitting frequency.


Title: RE: Which amp to start with?
Post by: W9IQ on January 24, 2017, 12:43:02 PM
Alex,

The assertion:

Quote
This is exactly why remote tuner is a must when antenna is not resonant at or near transmitting frequency.

is not a universal one. It is far more common to put the tuner at the transmitter end. If the attendant losses in the transmission line are acceptable then placing the antenna tuner at the transmitter end will have no ill effect other than the additional loss. As W8JX exemplified, it is quite possible to obtain minimal losses in coax despite higher SWR.

- Glenn W9IQ


Title: RE: Which amp to start with?
Post by: KOP on January 24, 2017, 02:41:40 PM

I have never heard of someone being killed by a tube amp ~snip

...oh really ?


but thousands have died from 120 volt wall current.

No question. However are you referring to ALL deaths from 120 volt wall current or just "amateur licensee" related deaths ?

It's not like you to paint such a broad brush across something so specific John.

To the OP  , sorry for the necro post but I've been away from the home station for a bit .
Myself I would build an amp but I full well realize that isn't for everyone . So far you have plenty of feedback from the membership without my adding to the confusion . I'll just offer that whatever you do it should be tube , within budget , somewhat better than PL519's and no less than the 811/572B with the 500Z (X2?) a possibility .In any case contact a local club with the intent of finding an Elmer that can assist in person . 



Dennis


Title: RE: Which amp to start with?
Post by: N6YFM on January 24, 2017, 03:26:19 PM
Cool thanks. Which model? Single or dial core, 1-31 or 1.5 to 54?

Im going to assume 1.5 to 54 to cover 6m, dual core.


Quote from: NI0C li :)nk=topic=113083.msg974213#msg974213 date=1484523500
Here's what I use: http://www.balundesigns.com/feedline-isolation-baluns/

I like that Balun Designs publishes graphs of choking impedance versus frequency, so you know what performance you are getting.

With your current setup already in place Chris, my suggestion would be to purchase a FT240-43 core, and wrap your coax round it as many times as you can.

Steve G3TXQ has published the design graphs, you can see them here:
http://www.karinya.net/g3txq/chokes/

I have used both his 12 Turns on FT240-43 & 11 Turns on 2x FT240-52.  Both provide excellent common mode blocking performance as advertised.

Given that you can pick up a FT240-43 core for ~$10 USD, and just pass your coax through it a few times, I'd try that first before investing in a commercial version of what you can probably make yourself with Steve's published designs.

The 11 Turns on 2x (stacked) FT240-52 cores is probably the closest to an 'ideal' balun you can get, it is however a bit more costly to purchase as you need 2x 52 material cores.  However, if wound with teflon coax, it should be good for well over 2kw continuous into reasonable (SWR < 5:1) loads. 

The current 11T/2xFT240-52 Balun I use tested fine (no heating or insulation breakdown) at 1.3Kw into my dummy load.  It has not failed in service at 400 Watts PEP with ANY load.

By comparison, my a commercial Kenpro '1Kw CW' balun I had failed instantly when I tried putting 400 Watts PEP into a non resonant load.

I can't stress enough how much the Amateur community owes Steve G3TXQ for his work testing various designs and publishing them. Thanks Steve, hope you're well!

So, a newbie question about making the chokes on an FT-240 core;

The RG-400 coax specification call for a minimum "RADIUS" of 1", not diameter.  Radius.
But if you put 12 tight turns on an FT-240-xx ferrite core, it looks to me like that would
be a roughly 1 inch diameter, 1/2 inch radius?     I did not notice in the chart or details
if you wrap the coax loose around the FT240 core so that it maintains a 2 inch diameter?

Does anyone else have experience making these?   Do you use 2 inch diameter turns
through the core to meet the coax specified bend radius?   If not, I would think that at
power, as the cable heats up, the center conductor would migrate and short out?

Thanks,

Neal


Title: RE: Which amp to start with?
Post by: W9IQ on January 24, 2017, 04:05:26 PM
Neal,

You will often see baluns made with larger loops on the outside of the core for this reason. It isn't quite as "pretty" looking but it works.

- Glenn W9IQ


Title: RE: Which amp to start with?
Post by: KB1SNJ on January 24, 2017, 04:11:39 PM
I feel you are making a mistake somewhere. You need to consider coax feed line and antenna separately. On one side, you need to make sure that coax is all good. For that, connect resistor of 450 ohms to output terminals of your balun instead of antenna wires. Then use analyzer to check how it all looks like from your shack. You should have SWR below 1.2 and very small X value. If it is not the case, then problem is with coax line or balun. When this is cleared, connect wires back to balun and now use analyzer to measure antenna impedance at input of balun. That will show you how antenna really works at different frequencies.

475K Ohm resistor in place of antenna after 9:1 UNUN and choke.

(https://c1.staticflickr.com/1/625/32468574626_8585034d7f_n.jpg) (https://flic.kr/p/Rt8W3N)475ohm 20170124_184826 (https://flic.kr/p/Rt8W3N) by Chris P (https://www.flickr.com/photos/143794395@N08/), on Flickr

(https://c1.staticflickr.com/1/530/32468574646_5ee73e6f1f_n.jpg) (https://flic.kr/p/Rt8W49)475k resistor 20170124_185423 (https://flic.kr/p/Rt8W49) by Chris P (https://www.flickr.com/photos/143794395@N08/), on Flickr

(https://c1.staticflickr.com/1/364/32387258731_0a194dbd8f_n.jpg) (https://flic.kr/p/RkXaEB)475k resistor 20170124_185403 (https://flic.kr/p/RkXaEB) by Chris P (https://www.flickr.com/photos/143794395@N08/), on Flickr

(https://c1.staticflickr.com/1/734/32387258781_efb2fe8ec6_n.jpg) (https://flic.kr/p/RkXaFt)475k resistor 20170124_185341 (https://flic.kr/p/RkXaFt) by Chris P (https://www.flickr.com/photos/143794395@N08/), on Flickr

(https://c1.staticflickr.com/1/657/32468574746_3ae1a7e7a7_n.jpg) (https://flic.kr/p/Rt8W5S)475k resistor 20170124_185453 (https://flic.kr/p/Rt8W5S) by Chris P (https://www.flickr.com/photos/143794395@N08/), on Flickr








Title: RE: Which amp to start with?
Post by: VK3BL on January 24, 2017, 04:26:37 PM

475K Ohm resistor in place of antenna after 9:1 UNUN and choke.


Hey Chris,

It looks like you've done very extensive testing - good job!

Did you try adding radials and moving all the excess feed line to the ground?  You may be surprised by the results RFI wise. 


Title: RE: Which amp to start with?
Post by: KB1SNJ on January 24, 2017, 04:30:49 PM
thanks, I followed with what was suggested by AC2RY, but not sure what he means by "very small" X value and I only think X value is reactance. Certainly the SWR is nowhere near what he was looking for!  Hoping some more comments will build a consensus from this result. The post implied there is an "issue" with the feedline somehow if the numbers werent as expected. I dont know what "very small" value is on reactance though as this is all brand new to me.


Title: RE: Which amp to start with?
Post by: W8JX on January 24, 2017, 04:35:22 PM

I have never heard of someone being killed by a tube amp ~snip

...oh really ?

Name  one....


Title: RE: Which amp to start with?
Post by: W9IQ on January 24, 2017, 04:54:05 PM
Chris,

Was that a 475k ohm resistor or 475 ohms?

- Glenn W9IQ


Title: RE: Which amp to start with?
Post by: KB1SNJ on January 24, 2017, 04:58:45 PM
475K... oh... OOPS!!!!!!!!!!!!!!!!!!!!!

stand by!    :o


Title: RE: Which amp to start with?
Post by: KB1SNJ on January 24, 2017, 05:23:53 PM
450 OHM in place of antenna, results way different!

(https://c1.staticflickr.com/1/369/32131295870_3e5d854dc0_n.jpg) (https://flic.kr/p/QXkhPQ)20170124_201037 (https://flic.kr/p/QXkhPQ) by Chris P (https://www.flickr.com/photos/143794395@N08/), on Flickr

(https://c1.staticflickr.com/1/767/32510109865_0a24db2f9c_n.jpg) (https://flic.kr/p/RwNP2B)20170124_200831 (https://flic.kr/p/RwNP2B) by Chris P (https://www.flickr.com/photos/143794395@N08/), on Flickr

(https://c1.staticflickr.com/1/722/31666632974_d737b65fe7_n.jpg) (https://flic.kr/p/QfgLJA)20170124_201118 (https://flic.kr/p/QfgLJA) by Chris P (https://www.flickr.com/photos/143794395@N08/), on Flickr

(https://c1.staticflickr.com/1/563/32131295830_1a37eb9f80_n.jpg) (https://flic.kr/p/QXkhP9)20170124_201108 (https://flic.kr/p/QXkhP9) by Chris P (https://www.flickr.com/photos/143794395@N08/), on Flickr

(https://c1.staticflickr.com/1/696/31666633044_591a5d8d25_n.jpg) (https://flic.kr/p/QfgLKN)20170124_201056 (https://flic.kr/p/QfgLKN) by Chris P (https://www.flickr.com/photos/143794395@N08/), on Flickr

(https://c1.staticflickr.com/1/596/32510109525_f89fc7113a_n.jpg) (https://flic.kr/p/RwNNVK)20170124_201137 (https://flic.kr/p/RwNNVK) by Chris P (https://www.flickr.com/photos/143794395@N08/), on Flickr



Title: RE: Which amp to start with?
Post by: W9IQ on January 24, 2017, 05:28:29 PM
Chris,

Everything looks good!

- Glenn W9IQ


Title: RE: Which amp to start with?
Post by: KB1SNJ on January 24, 2017, 07:46:17 PM
Chris, Everything looks good!
- Glenn W9IQ

With the feedline at least! I wonder if I suspend the G5RV higher than spec so its steeper, but broadsided to the East/West, what that configuration would to to the propagation takeoff angle and pattern, and what the gain would be? My upper pulley is around 53ft, and the ladder line center section calls for 32ft of height. Other than that I'll have to scroll back and look at the various small-lot suggestions in this thread.


Title: RE: Which amp to start with?
Post by: AC2RY on January 24, 2017, 08:36:18 PM
Chris, Everything looks good!
- Glenn W9IQ

With the feedline at least! I wonder if I suspend the G5RV higher than spec so its steeper, but broadsided to the East/West, what that configuration would to to the propagation takeoff angle and pattern, and what the gain would be? My upper pulley is around 53ft, and the ladder line center section calls for 32ft of height. Other than that I'll have to scroll back and look at the various small-lot suggestions in this thread.

You should not worry about take off angles yet. Just make antenna more or less working at bands you want to use. I still strongly recommend remote tuner. For me it makes almost miracles. I do not see why it should not work for you. Here are my results with remote tuner on and off - I use ZS6BKW (longer version of G5RV) after 150 feet of LMR400. I had similar results with 47 feet vertical and ground provided by 5 rods within few feet from each other - just not as good on 80 meters.

(https://lh5.googleusercontent.com/eXhZmLNDVCFdh4w2afsmTu27KzjtLfboAlvRiefSNN_sEtuej_vKVB4qjzaKWp3HHHBHPMDl=w1855-h951)

(https://lh6.googleusercontent.com/IXK3fSX_7NVKtjbGQs1dbVOC0CT5dCRqT6C8obbCspnzazYCKdTs6XyIB9eWEzK8Ze6zWFi3=w1855-h951)

(https://lh4.googleusercontent.com/Q_5r5W1VqK2nGZuSOb0XFvNXRUZtqJLLfDTCRRdoufC6gWkF1EsUvr_oJMkDK-Tv9LP_5JPd=w1855-h951)

(https://lh4.googleusercontent.com/WLqXea5oAiG8CSpoIocNkiCVIWcVnbtc8xS8KQ9dYzCw-iuw6cCFiHwOvkjULUcTR4DBHBfK=w1855-h951)



Title: RE: Which amp to start with?
Post by: KOP on January 24, 2017, 11:54:53 PM

I have never heard of someone being killed by a tube amp ~snip

...oh really ?

Name  one....


https://apps.fcc.gov/edocs_public/attachmatch/DOC-338447A1.pdf

Last page ...

"
On September 13, 1938, Ross Hull, Editor of QST, died after being
electrocuted in his home. He had been working on a homebrew TV receiver.
Ross was a native of Australia and held the call 3JU while living "down
under". He did not hold a U.S. license because his citizenship
application was not finalized. Despite his lack of American Amateur
privileges, Ross Hull was instrumental in early VHF/UHF developments.
He designed practical and inexpensive 5 meter stations, and greatly
contributed to the knowledge of VHF/UHF propagation. His death
dramatically pointed out the dangers of working on live circuits and,
for months thereafter, QST ran articles on how to "switch to safety".”

http://billingsgazette.com/news/state-and-regional/wyoming/wyoming-engineer-electrocuted-at-transmitter-site/article_935c0815-a742-5fbf-a473-d188c542d815.html

commercial but dead none the less


http://www.qsotoday.com/podcasts/4x1tq

4X1TQ a near miss ...

John , there are others but I’ll leave due diligence to the curious or the unwary .

Dennis 


Title: RE: Which amp to start with?
Post by: KB1SNJ on January 26, 2017, 11:09:11 PM
Just a quick update, I tossed that coil of extra feedline that was on the fence post to the ground the other day. Made no other changes. And I just tuned up and greatly reduced interference with the monitor (almost gone) nor the audio in the mixer unit (I can use it again). Thats at full 100w output, 80m and 40m so far. I should remove the new choke tomorrow and test it again without.

EDIT: 160 will no longer tune up with the internal tuner, SWR is above 5:1  - it used to tune above about about the halfway point in the 160m band. I wonder how I can get that antenna to cooperate again there?


Title: RE: Which amp to start with?
Post by: KC8KTN on January 26, 2017, 11:41:42 PM
Take from me a good amp to start with is a kenwood tl-922 look for a good one in good shape.Contact lou@qroking.com his name is Lou he can help you out.Tell him chuck sent you kc8ktn with the ken wood tl-922 .He helped me . Awesome guy awesome amp he will not steer you wrong.Long live ham radio.My Email is kc8ktn@hotmail.com.


Title: RE: Which amp to start with?
Post by: VK3BL on January 27, 2017, 12:16:48 AM
Just a quick update, I tossed that coil of extra feedline that was on the fence post to the ground the other day. Made no other changes. And I just tuned up and greatly reduced interference with the monitor (almost gone) nor the audio in the mixer unit (I can use it again). Thats at full 100w output, 80m and 40m so far. I should remove the new choke tomorrow and test it again without.

EDIT: 160 will no longer tune up with the internal tuner, SWR is above 5:1  - it used to tune above about about the halfway point in the 160m band. I wonder how I can get that antenna to cooperate again there?

Sometimes, its the simple things that make all the difference with RFI.

Most likely it used to tune up due to interaction between the driven element and the feed line, which has now been solved.  Ergo, it never really tuned up on 160M; not in any usable sense.

I've never had an antenna that would tune up on 160M at QRO Levels, so others may be in a better position to comment.  That said, I would suspect with a 50ft radiating element, quite a stout tuner would be required - just have a look at some of the matching components on 160M verticals, they're huge.



Title: RE: Which amp to start with?
Post by: W9IQ on January 27, 2017, 03:21:58 AM
Chris,

If 160 meter operation is a goal for you, you will probably find that a large airwound inductor at the base of the antenna will put it in range for your tuner. The inductor can simply be shorted out for the other bands.

If you take the R and X readings for 160 meters at the base of the antenna, these can then be used to calculate the parameters for an appropriate inductor.

It is great news that you are working your way through the RFI problems. Don't forget to make air coil chokes out of your excess coax. There is no downside to "too much" choking.

- Glenn W9IQ


Title: RE: Which amp to start with?
Post by: KB1SNJ on January 27, 2017, 09:13:11 AM
OK something is very bizarre here with regard to the RFI. It was always jamming my monitor, often knock it offline or at a minimum, severe shimmering.  Now it is barely touched when keying up with the same 100w on the same antenna on the same bands (80/40).

I was excited to think it was this new choke I made from the advice in this topic, which had no effect initially but after dropping the extra feedline to the ground, monitor issue went away.

Well I just put the feedline somewhat back on the fencepost as it was, no RFI. Removed the choke, no RFI! Then I remembered I had reconnected the ground to the radio chassis, so I popped that back off, no RFI.

As far as I can tell, the bad RFI scenario has been replicated and yet the monitor is now 95% unaffected. So is my ROLLS headphone mixer which I previously could not use. Now its useable again.

FTDX3000 => 3ft coax => AlphaDelta 4-way Switch => long bunched up feedline => choke and 9:1 UNUN => 50+ ft vertical wire, and 8ft ground rod with two odd radials on ground.

Feedpoint is about 5ft off the ground with single solid 14ga wire down to ground rod/radials.

I still get some moderate screen shimmering and mixer interferance on 20m.

More experimenting to do I guess!

As to the reactance on 160M question:

(https://c1.staticflickr.com/1/757/32402203342_138f6799f8_n.jpg) (https://flic.kr/p/RngLbj)160M at feedpoint 20170127_114129 (https://flic.kr/p/RngLbj) by Chris P (https://www.flickr.com/photos/143794395@N08/), on Flickr



 






Title: RE: Which amp to start with?
Post by: AC2RY on January 27, 2017, 09:29:56 AM
OK something is very bizarre here with regard to the RFI. It was always jamming my monitor, often knock it offline or at a minimum, severe shimmering.  Now it is barely touched when keying up with the same 100w on the same antenna on the same bands (80/40).

I was excited to think it was this new choke I made from the advice in this topic, which had no effect initially but after dropping the extra feedline to the ground, monitor issue went away.

Well I just put the feedline somewhat back on the fencepost as it was, no RFI. Removed the choke, no RFI! Then I remembered I had reconnected the ground to the radio chassis, so I popped that back off, no RFI.

As far as I can tell, the bad RFI scenario has been replicated and yet the monitor is now 95% unaffected. So is my ROLLS headphone mixer which I previously could not use. Now its useable again.

FTDX3000 => 3ft coax => AlphaDelta 4-way Switch => long bunched up feedline => choke and 9:1 UNUN => 50+ ft vertical wire, and 8ft ground rod with two odd radials on ground.

Feedpoint is about 5ft off the ground with single solid 14ga wire down to ground rod/radials.

I still get some moderate screen shimmering and mixer interferance on 20m.

More experimenting to do I guess!

As to the reactance on 160M question:

(https://c1.staticflickr.com/1/757/32402203342_138f6799f8_n.jpg) (https://flic.kr/p/RngLbj)160M at feedpoint 20170127_114129 (https://flic.kr/p/RngLbj) by Chris P (https://www.flickr.com/photos/143794395@N08/), on Flickr



 






Well, now analyzer shows what it should at 160M - your vertical is unusable at that band. You need to have at least 100 feet (could be inverted L) at get decent transmission, and even that will only be able to do with external tuner or tuning coil at the base of antenna. I suggest forget about 160M for now. Make your antenna working on higher bands first.


Title: RE: Which amp to start with?
Post by: W9IQ on January 27, 2017, 11:50:06 AM
Chris,

It sounds like you have some more work to do on the basic antenna yet to determine the ingress mode of the RFI. It would be good to get that all squared away before making any other changes.

Your antenna may not be very efficient on 160 meters although it would work to some degree. Using the numbers from your analyzer, if you have an inductor of approximately 8.6 uH in series with the center conductor and a 0.004 uF capacitor from the center conductor to the braid on the transmitter side of the inductor, you would have an SWR very close to 1:1 on at 1.8 MHz. Remember though this is not an indication of the efficiency or effectiveness of the antenna.

A nice inductor could be fashioned from winding 1/4 copper tubing around a scrap piece of 4" schedule 40 PVC pipe. The tubing is self supporting when done so it doesn't require a form to keep it in shape. Drill a hole at one end of the pipe to hold the beginning of the tubing. Start winding and space the turns 1/2" apart. Wind 12 turns (or more) in total - this will take about 8 feet of tubing and result in an inductor of 6 inches in length. Remove the 4" pipe after winding the coil. When you take the coil off the pipe, it will expand a little bit. You can experiment with where to tap off the coil to get the lowest SWR. You should find it at a spot around 10 turns depending on how much the coil expands after removing it from the pipe.

If you get more serious about 160 meters, then you will want to plan a better antenna for that band in the future.

Have fun.

- Glenn W9IQ


Title: RE: Which amp to start with?
Post by: KB1SNJ on January 27, 2017, 06:03:00 PM
Thanks Glenn! I went to home depot and bought 10ft of 1/4" copper and a short piece of 4" pvc and wound it around. But I only got 8 turns, and the final diameter is 5" (the pipe is almost 4.5" OD and the coil expanded slightly when released). According to an online inductance calc, this produces 6.95uH when squished down to 3.5" length. Can I work with that perhaps by changing the capacitor value? Alternatively, would that possibly get the SWR within range of the tuner (3:1 or less)?

i know this wont be an efficient radiator but neither is a screwdriver antenna on 80 or 40 and those are used all the time. Can the radiation efficiency be calculated? (Still have *no clue* on using EZNEC demo, just tried again!)

Chris

Chris, Using the numbers from your analyzer, if you have an inductor of approximately 8.6 uH in series with the center conductor and a 0.004 uF capacitor from the center conductor to the braid on the transmitter side of the inductor, you would have an SWR very close to 1:1 on at 1.8 MHz. Remember though this is not an indication of the efficiency or effectiveness of the antenna.

A nice inductor could be fashioned from winding 1/4 copper tubing around a scrap piece of 4" schedule 40 PVC pipe. The tubing is self supporting when done so it doesn't require a form to keep it in shape. Drill a hole at one end of the pipe to hold the beginning of the tubing. Start winding and space the turns 1/2" apart. Wind 12 turns (or more) in total - this will take about 8 feet of tubing and result in an inductor of 6 inches in length. Remove the 4" pipe after winding the coil. When you take the coil off the pipe, it will expand a little bit. You can experiment with where to tap off the coil to get the lowest SWR. You should find it at a spot around 10 turns depending on how much the coil expands after removing it from the pipe. Have fun.

- Glenn W9IQ


Title: RE: Which amp to start with?
Post by: KB1SNJ on January 27, 2017, 07:16:07 PM
like this?

(https://c1.staticflickr.com/1/362/32521274766_0c113b14f3.jpg) (https://flic.kr/p/RxN2XU)vertical antenna board (https://flic.kr/p/RxN2XU) by Chris P (https://www.flickr.com/photos/143794395@N08/), on Flickr


Title: RE: Which amp to start with?
Post by: W9IQ on January 28, 2017, 05:02:35 AM
Hi Chris,

The diagram isn't correct. The capacitor should go between the bottom end of the coil and the braid of the coax at that point.

You can experimentally check the SWR with your coil and capacitor by using your antennalyzer. I can run the numbers for you later this weekend to let you know what the model predicts.

- Glenn W9IQ



Title: RE: Which amp to start with?
Post by: VK3BL on January 28, 2017, 05:12:20 AM

It is great news that you are working your way through the RFI problems. Don't forget to make air coil chokes out of your excess coax. There is no downside to "too much" choking.

- Glenn W9IQ

Glenn,

This isn't strictly true.  As Steve G3TXQ points out on his website, "ugly balun" / air wound coax chokes are often highly reactive, and can make problems worse. 

As a general rule, the only time coax should be coiled is on a roll in the store; there are much better ways of building chokes. :)



Title: RE: Which amp to start with?
Post by: W9IQ on January 28, 2017, 05:28:40 AM
Jarrad,

Your point is well taken. If the design does not present an RS that is greater than XS than it may do more harm than good.

- Glenn W9IQ


Title: RE: Which amp to start with?
Post by: AC2RY on January 28, 2017, 07:55:19 AM
like this?

(https://c1.staticflickr.com/1/362/32521274766_0c113b14f3.jpg) (https://flic.kr/p/RxN2XU)vertical antenna board (https://flic.kr/p/RxN2XU) by Chris P (https://www.flickr.com/photos/143794395@N08/), on Flickr

This does not look right. Going from feedline you should have choke first, then balun, then coil. But generally, if you do not want to use external tuner (I still do not see why - this is less than $300 to try), you need to build something like matching circuit described here http://www.ad5x.com/images/Articles/Match43footerRevA.pdf


Title: RE: Which amp to start with?
Post by: KB1SNJ on January 28, 2017, 11:27:30 AM
Thanks, I need to get this right (If I really want to dabble in 160M with my vertical, and there is a local net on 160M if it's still active, that I was invited to a while back) and build a rebust implementation of the above once I get it right.


As to the external tuner, I'm not up with that yet as it's quite a lot of money and the antenna is not sorted yet. Also, my next tuner should be able to handle an eventual amplifier so I'm thinking that will be more than $300 unless I find one used.  My receiver has a modest internal tuner that handles this vertical on all (I think) but 160 right now, and on the shelf I have that MFJ auto tuner, not to mention a manual tuner - all 100 watt tuners.

Originally when I started the amplifier question, it was about boosting this 50+ ft vertical because its not efficient and I have few options due to very small lot. So if I could match it and add power then 20% efficiency becomes like 40% or whatever, on transmit.

The sidetrack came from the RFI issues (which for some bizarre reason seem lessened). I may be able to swing the base of the wire a little more away from my shack although that will take the wire off vertical.

This thread provided some ideas on choking, at that G3TXQ web page in particular, gave me some good amp ideas, reminded me I will need a higher power tuner, and some antenna ideas. Already have made Glenn's coil but needed more copper tubing, maybe if he chimes back on that I can still use it to at least try 160.

I can lay down a couple more vericals but they will really only be in two directions East and North.

One benefit of the 50ft vertical wire is that it's simple and takes almost no space.

I also read about a 30ft 160M vertical made of pvc pipe wrapped with 1/2 wave on 160 with a simple cap hat, could always try something like that and pull it up via the pulley. Can even go 40ft (4 sections).  I wonder if a single wire antenna could be in the middle for the other bands on its own feedline and switch them? Would the RF simply be "captured" by the coiled outer antenna even if it's switched out?















  


Title: RE: Which amp to start with?
Post by: W9IQ on January 28, 2017, 11:39:57 AM
Chris,

My description is correct. The capacitor is across the coax cable just before it heads to the radio. The inductor is between the capacitor and the vertical element. I do agree that the choking balun should be on the radio side of the coax.

It is a busy weekend for me but I will post a sketch later this weekend just to clarify.

- Glenn W9IQ


Title: RE: Which amp to start with?
Post by: KB1SNJ on January 28, 2017, 03:42:18 PM
OK I winded 15turns air choke per the G3TXQ page, reinstalled the antenna without the new choke.

Now the RFI affecting the monitor again BUT it could tune up on 160M. Hmmmm. 

I reinserted the fancy new ferrite choke and it seemed to lessen the RFI modestly but it still distorts the monitor on 160/80/40/20.  But with the ferrite choke it will no longer tune up on 160!

I cant figure out why there was no RFI effects on the monitor yesterday and now there is. Perhaps the way the feedline is bunched up???  Cant think of other variables that have changed.

Hopefully I can learn enough working with this wire to get some antenna control and then set the stage for adding an amplifier.


Title: RE: Which amp to start with?
Post by: W9IQ on January 28, 2017, 05:28:36 PM
Chris,

Based on your description of on-going RFI issues, I strongly encourage you to fix these first before you move onto 160 M operation. The reason is that it is likely that the changes you make to get rid of the RFI will also affect the matching circuit needed for 160 M operation.

What is the brand and model number of that grey coax in the photo? How old is it? How much excess coax do you have wound up?

Some thoughts to help with your RFI:

1.) Add more radials. The more you get down, the better - especially if they are very short.
2.) Build another ferrite balun and install it just before your coax enters the house.
3.) Shorten your coax cable run to the length that is actually needed.

With regard to the 160 M matching circuit we have been discussing, the schematic is below (I didn't show your 9:1 balun that should be considered part of the vertical element). This design is an "L matching circuit" specific to 160 M. You would need to remove it to work other bands. I would suggest building this with a PL-259 on the antenna end and an SO-239 on the coax end. Very short lengths of coax cable to make this is OK. This way you can just open the connection between the antenna and the balun to insert this circuit when you are operating 160 M.

Again, I recommend you solve the RFI first before starting the work with this circuit. Once the RFI is solved, retake your antennalyzer readings at the base of the antenna to confirm the design of the 160 M matching circuit.

(https://c1.staticflickr.com/1/630/32200173550_d1c3223acd_z.jpg)

I hope that helps.

- Glenn W9IQ


Title: RE: Which amp to start with?
Post by: VK3BL on January 29, 2017, 01:13:15 AM
OK I winded 15turns air choke per the G3TXQ page, reinstalled the antenna without the new choke.

Now the RFI affecting the monitor again BUT it could tune up on 160M. Hmmmm.  

Chris,

As Glenn said, you need to approach these two problems separately.

If I may stress this, it is that your 50ft element alone (without matching components at the base) WILL NOT tune up on 160M when properly choked.  Period.  If it is tuning up on 160M, it means you have an issue with common mode appearing on your feed line due to inadequate choking.

What is happening is the feed line is becoming part of the radiating element, and your "real antenna" is much larger than 50ft.  Thats why it tunes.

The problem with the feed line becoming part of the radiating element, is that it radiates in the shack, and you get RFI.  That is not a trade I would make to have 160M operation, and as such, no station I have ever built has operated on 160M to date.  I just haven't had the real estate for a proper sized 160M antenna, nor have I had the motivation to build a proper matching network at the base of an electrically short element.

If you must have 160M operation at your station, my advice would be to build a seperate 160M antenna, using the coil loading Glenn has advised.  You may also use the same antenna on 80M, if you substitute your lumped components.

Bear in mind, all of the problems you're having now get much worse with QRO.  Thats the challenge of QRO and why us QRO types do it.  We know our antenna systems are working within design parameters, because if they aren't, it causes very noticeable issues.  As you have found, those issues are often not easy to solve without a sacrifice.  With all certainty, the dream of a DC to Daylight all band super antenna is one of them.

  


Title: RE: Which amp to start with?
Post by: W9IQ on January 29, 2017, 09:09:31 AM
Chris,

I forgot to answer your question about the inductor value. If in fact your inductor is 6.95 uH then it cannot be used for the matching circuit. It would be better to wind too large (long) of a coil and find the right tap on it for 160 M matching.

- Glenn W9IQ


Title: RE: Which amp to start with?
Post by: KB1SNJ on January 30, 2017, 09:52:57 PM
thanks a million guys, glenn for the diagram and calc on the coil. I will get 10 more feet and a couple and add that on. jarrad thanks for the explanation of the 160 match with no choke.

by working with this piece of wire I am starting to get the fundamentals just a bit.

I will try to add a couple more radials (really can only go in one more direction), and later apply the diagram and longer coil etc. and another choke. the monitor distortion is a good "tool" for seeing RF in the room. I suppose that could also be from the radiating element itself. not sure how to tell the difference just yet.

it seems that 50ft of wire straight up should be able to do something when little screwdriver antennas work for people down to 80M

I also found a youtube vid that steps through using EZNEC, so now I can try to get used to that!

btw I stumbled onto this talks about using smaller verticals on 80/160. key takeaway is use radial system and expect low net ERP. (Although 5% of 600W is 30W)

http://www.eham.net/ehamforum/smf/index.php?topic=81071.0;wap2 (http://www.eham.net/ehamforum/smf/index.php?topic=81071.0;wap2)





Title: RE: Which amp to start with?
Post by: VK3BL on January 31, 2017, 06:08:10 AM

it seems that 50ft of wire straight up should be able to do something when little screwdriver antennas work for people down to 80M

btw I stumbled onto this talks about using smaller verticals on 80/160. key takeaway is use radial system and expect low net ERP. (Although 5% of 600W is 30W)


Thanks for the kind words Chris.  Its been an enjoyable thread, and I think you're doing a great job learning about things.

The only thing I will add is that it isn't necessarily as simple as just settling for a low ERP, especially if you wish to use an amplifier one day.  The thing you have to understand, is that if you're only radiating say 5% of the power, that means the other 95% is being lost somewhere.

Now, at 100 watts, losing 95% of it in a little screwdriver probably isn't a huge deal, especially in SSB / PEP modes.  However, if you were to run 1000 Watts input into the system, suddenly it has to deal with 950 watts of essentially heat; thats going to demand some serious sized components.

50ft is a nice sized radiator, don't get me wrong, but on 160M, its about 1/10th of a wavelength; well and truly on the electrically short side.

I'm not trying to discourage you - its definitely doable, just don't underestimate the power handling required of the matching components. 

It sounds like you're on the right track with the 1/4 inch copper.  Most of the loss will be in the coil, and 1/4 inch should handle it just fine.


Title: RE: Which amp to start with?
Post by: W9IQ on January 31, 2017, 06:18:18 AM
I would view the losses on 160 meters coming primarily from ground losses due to an inadequate radial system.

- Glenn W9IQ


Title: RE: Which amp to start with?
Post by: KB1SNJ on January 31, 2017, 12:13:08 PM
hi glenn what does that mean?  lets say 900 watts being "lost" and under your post thats "ground losses" what does that really mean, that electrical energy is going down into my ground rod, and the 3 radials? or a percentage thereof, with the rest converted to heat in the "loading coil" (if thats what the copper coil is properly called)?

by the way just to keep this on track, 160m is not a priority here at all. not looking to do much radio with it but making that coil and capacitor setup etc, and discussing it is the real benefit as the principles apply to any situation of running an antenna electrically shorter than the 1/2 wavelength (I think). it seems from this recent posts that if the wire is 1/10 wavelength, then building a loading coil creates a nonradiating section that absorbs (and converts to heat) the radio frequency rather than just reject it back the other way?  but then there's the ground losses aspect which glenn mentioned.

which then (sorry) makes me wonder if there was no ground or radials at all, just the wire and loading coil, what happens to the radio energy situation then?



I would view the losses on 160 meters coming primarily from ground losses due to an inadequate radial system.

- Glenn W9IQ


Title: RE: Which amp to start with?
Post by: W9IQ on January 31, 2017, 01:11:42 PM
Chris,

The earth under our feet is really a poor conductor of RF energy. For a vertical antenna this means that if there is not a sufficient ground plane or counterpoise that a part of your RF transmit power is heating the earth as it tries to find a return path. This also means that the RF energy will search out other lower reactance paths. In your case it has found the shield on the outside of your coax to be one of those paths so as a result, you have common mode current. The balun that you built puts a high reactance (specifically high resistance) into the outer shield to discourage this as a return path.

There will also be other losses due to the resistance of the antenna components, the inefficiencies of your unun, etc. Some of these will become much more apparent if you apply high power to your antenna. Things that have sufficient resistance will melt and things that cannot handle the higher voltage will arc. This is why several respondents, including me, on this thread have recommended getting everything cleaned up first before you consider going QRO as this will tax everything in your antenna system.

Specific to the 160 meter coil, in itself it will not represent any significant percent of loss of the overall antenna system. But consider that your radials will become even more inadequate at those lower frequencies so the effects mentioned earlier could become worse.

- Glenn W9IQ



Title: RE: Which amp to start with?
Post by: N1ZPY on February 02, 2017, 03:48:38 PM
If you don't mind going out to the base of the ant to change bands some ideas from this ant might help. .http://www.arrl.org/files/file/Technology/tis/info/pdf/7806016.pdf


Title: RE: Which amp to start with?
Post by: KM1H on February 03, 2017, 08:21:01 AM
Chris, you have received a wide range of ideas, from excellent to useless.

Here are a few of mine that are far from unique but well proven.

Single 3-500Z Amp:

Ameritron AL-80A or 80B. The original 80 is OK if it was factory updated.

Heathkit SB-1000, needs a few simple mods for 160 and WARC bands and is an almost clone of the AL-80A; Ameritron supplied most of the parts.

Amp Supply LK-450 Rugged and reliable

Several other single 3-500Z amps that were relatively low production but do show up at times. Im another who has no use for the AL-811 series until the friggin' Chinese stop shipping garbage.

Any amp that is 20-25 years and older should have the PS filter caps replaced and their are complete replacement board and parts kits available for many.

Several other vintage amps are fine but you should be aware that PM, repairs, and mods are often required. I use an old Dentron Clipperton L and DTR-2000L strictly as AM linears on a separate bench devoted to vintage "hollow state" gear from the 30's to 60's.

Carl
KM1H
Ham since 1955


RFI

Read and digest the info in these links, there is nothing better available and used by the serious hams who will not tolerate RFI while in a contest DXing, and otherwise dont want to be bothered by family or neighbors when on the air.

http://audiosystemsgroup.com/RFI-Ham.pdf    The latest update from K9YC

http://www.audiosystemsgroup.com/K9YC/K9YC-old.htm  Hours of good reading

Even the best of common mode suppression does not fully eliminate what radiates directly from electronics in your home and neighborhood. Snap On ferrites are by far the least effective and cost the most. I had to spend a lot more for ferrites on all sorts of power cords around the house as well as toss all the small switching PS wall warts and go back to old fashion linear versions. My Comcast modem and TV box plus a few larger switching supplies were the hardest and required being wrapped in aluminum foil where it wasnt blocking ventilation plus ferrite. A portable AM radio is best for noise hunting as is shutting off all but one circuit at a time at the main panel. Or shut all off and what remains is not from you but do all the feedline work first.



Baluns and ferrite cores:

Most of what is on the market is overpriced, junk or both. Especially stay away from Amidon and Palomar along with the big color ads in the rags which cost a lot of $$ to run and you are paying that premium. This is one area when homebrew is usually the best.

The 52 mix is 3X the price of 43 and offers very very little extra except on paper.

I always shop Mouser first and their Fair-Rite 2643803802 and 2631803802 are the best choices. If you really need the best at 160 use the 31 mix and you can also stack one or more of each mix for full 160-10M coverage. Most of my antennas are monoband or HB 2-3 band verticals so I use 31 for 80/160 and 43 for 30-6M.



Power Rating:
I would never use RG-58, 59, 6 or equivalent at even 600W since the voltages and currents may be excessive on chokes AND baluns and you wont know unless you try them. Any of the similar size Teflon coax is far superior in that application even if it does require an adaptor to go to the regular RG-213 or LMR-400 (or equivalent) feedline.


Title: RE: Which amp to start with?
Post by: KB1SNJ on February 05, 2017, 10:53:16 AM
OK a few dumb questions, as I make my way through the reading and resources above:

1) how to design (build) a 1.5 or 2kw (robust) unun thats 9:1
2) will a remote tuner unit do better job keeping the RF at the antenna and not coming back into feedline than inside tuner, or is that all a function of the chokes?
3) if I were to hoist an inverted vee by using 100ft of wire instead of 50 and bringing the other leg down say 35ft away, would that radiate better than a single wire, and what kind of impedence would be seen at feedpoint? (the broadside if applicable would face WSW which would be very good from New England)



While I make my way through the resources posted above (thank you!), I have a couple basic questions:

I now understand what the ratio is in my 9:1 UNUN, it reduces impedance by a factor of 9:1. So my wire must present an impedance of around 9 times 50 or 450 more or less depending on length and maybe other factors.

My question is that if I wanted to build a heavier duty (for more power) 9:1, how can I scale that up? I do know that Balun Designs sells a 2kw 9:1 but I'm going to guess that ferrite size and formula and also the gauge and number of wraps of the three wires affects the final results. I wonder how to measure a unun anyway? The post a few posts back told me to put a 450OHM resistor on the antenna size and check the coax input side ahhhhh that must be how to do it. So resistance is resistance whether it's a straight 50ft wire against ground or shunted through a resistor on the antenna side of the unun?


Title: RE: Which amp to start with?
Post by: AC6CV on February 05, 2017, 01:44:06 PM
If it were my shack I would first make sure my present antenna was properly matched and no RF in my shack or in nearby equipment. Then possibly think about an amp. I don't have any problems with working nets on 75 in my RV with my home brew  23 ft vertical and loading coil. However, it is properly matched and the load is resistive.


Title: RE: Which amp to start with?
Post by: K6AER on February 05, 2017, 01:54:34 PM
A 9:1 Balun, that will handle the RF voltage of 1.5 KW, will have to with stand 2500 volts on the output not to mention the heating of the toroids.  This assumes the antenna is somewhat resonate at that output impedance. This is a recipe for disaster. You need a more resonate antenna for the low bands when running power.  Not all locations will accommodate 160-80 meter operation. Most hams have multiple antennas to cover most of the bands. I addition you have never mentioned what local noise sources are in the area. Having a working antennas on the lower band will be a moot point if your noise floor is a non-workable level.

I noticed that we are up to almost 160 posting on this subject, 41 from yourself going back three weeks. I suggest you do some reading with the ARRL Antenna Handbook. It is not fair to ask the ham community to spoon feed you with knowledge when you have not taken the time to understand the basics. 


Title: RE: Which amp to start with?
Post by: N1ZPY on February 05, 2017, 02:29:47 PM
I would also suggest buying or borrowing an antenna analyser to help you with your antenna.  As many others have said you need to fix it before you add an amp. 


Title: RE: Which amp to start with?
Post by: AC2RY on February 05, 2017, 06:32:45 PM
I would also suggest buying or borrowing an antenna analyser to help you with your antenna.  As many others have said you need to fix it before you add an amp. 

He has a good one already. The problem is he does not fully understand how to use it. This is time for CHRISDX to seat and read BOOKS, not posts on forums.


Title: RE: Which amp to start with?
Post by: W9IQ on February 05, 2017, 06:34:18 PM
Chris,

A few thoughts on your questions.

You should determine if you even need the 9:1 unun. Take your antennalyzer out to the base of your antenna. Take and record measurements from all of the bands from which you intend to operate, with and without the balun.

The purpose of putting the tuner at the base of the antenna is to reduce the extra loss in the coax due to high SWR. It will do little to nothing in the way of reducing stray RF in your shack.

The inverted V is a good idea. It is a balanced antenna so this in itself should reduce the RF coming into your shack via the coax shield. Do install your homemade choking balun at the apex of the V. Do not guess at a length for the legs of the V - look it up or model it for the primary bands on which you wish to operate. The primary direction of a V antenna is out the opening of the V when the antenna is 1/2 wavelength long.

- Glenn W9IQ


Title: RE: Which amp to start with?
Post by: WW8X on February 07, 2017, 11:41:50 AM
Your lot sounds like mine. Very small city lot with virtually no room for a decent antenna. On my 2-story house, I roof-mounted a Hygain 5BTV vertical trap antenna using a tripod mount and two radials for each band spread across the roof shingles fastened with some clips to the shingles. I put a 6" x 10 turn coil in the coax at the feed point. I live in a valley of sorts, with hills on 3 sides – yet, on all 5 bands (10, 15, 20, 40 and 80) I can usually work any station I can hear with often surprisingly great signal reports. I use a Drake MN-2000 tuner and have had no RFI problems since day one. As others have said: you shouldn't consider an amp until you get your antenna and RFI issues solved.


Title: RE: Which amp to start with?
Post by: VK3BL on February 07, 2017, 04:03:40 PM
The inverted V is a good idea. It is a balanced antenna so this in itself should reduce the RF coming into your shack via the coax shield. Do install your homemade choking balun at the apex of the V. Do not guess at a length for the legs of the V - look it up or model it for the primary bands on which you wish to operate. The primary direction of a V antenna is out the opening of the V when the antenna is 1/2 wavelength long.

- Glenn W9IQ

Another thing I would add to Glenn's advice is do not be concerned about antenna pattern just yet. 

Whilst its 'sexy' to talk about patterns, and several manufacturers tout verticals as a solution, you have to be mindful of the overall Effective Radiated Power of any given antenna.

Eg, there is no point gaining 1dB at a lower take off angle using a vertical, if its Effective Radiated Power is 3dB down over a dipole.

With my own suburban block, I have never been able to install a vertical that has managed to outperform a dipole for DX.  99% of the time, the Inverted-V dipole is just as good with DX, but much, much stronger for local rag chews.

Its fun to play around with EZNEC etc, but the most important thing you should be paying attention to in your (our) situation is how easily the antenna can be fed on the bands we wish to use.



Title: RE: Which amp to start with?
Post by: KE4LJH on February 08, 2017, 06:47:40 AM
There are many very good comments here to consider. I have used many antennas over the years both HB and store bought. I now use HB wire antennas exclusively as I have learned over the years that one can make there own antennas more efficient by tuning feed line lengths and other elements of the "SYSTEM" to make the system as efficient as one can.

I believe you have a little ways to go before you purchase an amplifier. Don't get in a hurry.

Consider this, a few years into getting my license I wanted an amplifier. My Elmer's told me to wait. That it was more important that I spend time building my knowledge and experience and learning how to make an efficient antenna "SYSTEM". I waited sixteen years to buy an amplifier because the more I learned about building antennas and building my knowledge about grounding and efficiency the more efficient I was able to make my antenna systems and the happier I became without an amplifier.

Based on your comments, I would recommend investigating the efficiency of your antenna system and why you are having challenges with it. To the extent possible, try other vertical antennas. My experience with vertical antennas is both HB and the GAP Antenna. I loved the gap antenna for over 15 years. It is simple to maintain and will last. Mine did not wear out, it was stolen out of my yard when away on vacation. One cannot go wrong with a Gap Antenna. Call Gap Antennas. Talk about your issues with them. Let them know where you are and you want to learn. Do the same with other antenna manufacturers.

My thoughts, invest in a well thought out and designed antenna HB or purchased. Then tweak your "Antenna System" until you are satisfied with the efficiency. Stick with 100 watts for a little while longer.

Experiment Idea. If real estate area is an issue, pull out the magic wand. What kind of multi-band wire antenna would you use if you had the room. Find a park or the place of a friend where you can set up other wire antennas and experiment as a portable station. Consider a wire antenna that uses 450 ohm ladder line or 600 ohm parallel line as the feed system. These are the most efficient systems for multi-band wire antennas.

Consider: A 40 meter vertical ground plane antenna constructed of 450 ohm ladder line or heavy gauge wire. Feed the antenna with 450 ohm ladder line. This antenna is suspended in the air. No ground radials needed. It does have four ground planes.
This antenna would require a tree or other non metallic support. A fellow ham has this very antenna system in use in Oregon. He lives on the coast and has two hundred foot conifer trees on his property near a cliff. His antenna is designed for 160 meters. It is a simple quarter wave 160m ground plane fed with 450 ohm ladder line. 160m DX. this is his transmit antenna. His alternate receive antenna is a 160m dipole fed with 450 ohm ladder line. He switches to the horizontal antenna for most receiving as it is more quiet and less susceptible to QRM and other noise.

There is a great deal to learn. I hope my thoughts, thinking and ideas may be of use to you. Best wishes, see you on the bands. KE4LJH


Title: RE: Which amp to start with?
Post by: KB1SNJ on October 07, 2017, 04:40:26 PM
I know this is a half year old, but I had "life" get in the way. I now have a big roll of copper tubing with which to make the 160M add-on coil for the vertical.  I'm expecting no miracles but I should, by following the excellent advice in the preceding posts, get it to match on 160m.  The huge amount of QRM that seems to be around may make that the end of the story but we'll see.

As an aside, I almost purchased a 4 acre property in Foster, RI on a high elevation. It was a square lot, with a clearing in the center where the house is and lots of trees. I think it would have been a dream for radio hobby, but wasnt the right time (according to my CFO). Next spring may be another story.

Anyway thanks again to all the GREAT info posted here and I am re-reading it all.

73


Title: RE: Which amp to start with?
Post by: LUCYAJONES on October 07, 2017, 10:46:50 PM
I know general question but I've seen numerous options in the classifieds, just looking for ideas and experiences.

I have a very tight lot, with a 50ft vertical above a 9:1 unun running 100watts. I really do not have much antenna options, no space for a ground plane array either.

A lot of stations that I can hear, cant hear me. So I think an amplifier may help compensate for the antenna deficiency.

Thinking that 1000 watts would be good. I have had issues with RF in the house tripping GFCI, etc but when I went to the vertical it seems to have gotten better (although my computer monitor still goes wonky with 100 watts)

Anyway, I'd need a robust amplifier because I am going to make mistakes operating initially. Budget is also a big issue.

ideas? experiences?




Well, unless you wanted to start with a full stack and 100 watts of pain. It's a happily different situation for beginner ax slingers today