Call Search
     

New to Ham Radio?
My Profile

Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question

Operating
Contesting
DX Cluster Spots
Propagation

Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net

donate to eham
   Home   Help Search  
Pages: Prev 1 2 3 4 [5] 6 7 8 9 10 ... 12 Next   Go Down
  Print  
Author Topic: Which amp to start with?  (Read 46945 times)
KB1SNJ
Member

Posts: 139




Ignore
« Reply #60 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.
Logged
KK4YDR
Member

Posts: 673




Ignore
« Reply #61 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.
Logged
W6GRD
Member

Posts: 14




Ignore
« Reply #62 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.
Logged
VK3BL
Member

Posts: 1790


WWW

Ignore
« Reply #63 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.
Logged

J.D. Mitchell BA  - VK3BL / XU7AGA - https://www.youtube.com/ratemyradio - Honesty & Integrity
VK3BL
Member

Posts: 1790


WWW

Ignore
« Reply #64 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.
Logged

J.D. Mitchell BA  - VK3BL / XU7AGA - https://www.youtube.com/ratemyradio - Honesty & Integrity
KB1SNJ
Member

Posts: 139




Ignore
« Reply #65 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.
Logged
KB1SNJ
Member

Posts: 139




Ignore
« Reply #66 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]
Logged
W6GRD
Member

Posts: 14




Ignore
« Reply #67 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.
Logged
W8JX
Member

Posts: 13268




Ignore
« Reply #68 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.
Logged

--------------------------------------
Ham since 1969....  Old School 20wpm REAL Extra Class..
KB1SNJ
Member

Posts: 139




Ignore
« Reply #69 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


Logged
W6GRD
Member

Posts: 14




Ignore
« Reply #70 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 Huh 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.
Logged
W8JX
Member

Posts: 13268




Ignore
« Reply #71 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.
Logged

--------------------------------------
Ham since 1969....  Old School 20wpm REAL Extra Class..
VK3BL
Member

Posts: 1790


WWW

Ignore
« Reply #72 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.
« Last Edit: January 19, 2017, 07:52:54 PM by VK3BL » Logged

J.D. Mitchell BA  - VK3BL / XU7AGA - https://www.youtube.com/ratemyradio - Honesty & Integrity
W8JX
Member

Posts: 13268




Ignore
« Reply #73 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.
Logged

--------------------------------------
Ham since 1969....  Old School 20wpm REAL Extra Class..
K4RVN
Member

Posts: 261




Ignore
« Reply #74 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
« Last Edit: January 20, 2017, 08:22:43 AM by K4RVN » Logged
Pages: Prev 1 2 3 4 [5] 6 7 8 9 10 ... 12 Next   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.11 | SMF © 2006-2009, Simple Machines LLC Valid XHTML 1.0! Valid CSS!