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[Articles Home]  [Add Article]  

Help, I Need a Cheap HF Amplifier!

James Benedict (N8FVJ) on August 21, 2002
View comments about this article!

Ever try 75 meter SSB early to mid evening with 100 watts? Chances are your 'ham buds' won't even hear you (or do not want to hear you). Hey, 75 meter SSB is suppost to be the easy 'armchair copy' band. Same story on rare 15/10 meter DX. Although a beam antenna helps, the only problem is the 75 meter guys are using beam antennas with the same HF amp used on 75 meters last night and are lined up a mile deep! Perhaps it is time to get a HF amplifier even if you are not loaded with cash. Lets say you can afford $250 to $375, lets look at what is available.

HEATHKIT SB-200 or SB-201: This amp has to be the 'work horse' king of the bands and my first choice- value & cost. 80 to 10 meters (SB-201 is limited to 15M), this amplifier uses a pair of 572B/TL160 tubes. 100 watts input will produce 600 to 700 watts SSB PEP output on 75 meters. The tube replacement costs are still reasonable at less than $100 for two tubes. The 572B tube is fairly rugged with a large carbon type plate. The Heathkit built-in tuned input will present a good SWR match for your solid-state HF transceiver and has ALC control. The multi-function meter measures high voltage, SWR, relative output, plate & grid current. The amplifier is completely TVI shielded as well. The keying relay switches 120 VDC bias thus an interface relay must be used with most of the newer HF transceivers. Operation off of 120 VAC is ok, no expensive 240 VAC distribution is required. These amplifiers cost anywhere from $250 to $350 in good to excellent condition and are a bargain. Breakdowns are rare, perhaps a newer set of late model used B+ capacitors are in order- usually less than $20 for six (6) capacitors (this applies to all older amplifiers, just not Heathkit). Size is 14.75"w x 7.75"h x 14.75"d. The measurements includes extended front 'feet' and control knobs. Yep, got one on the desk in front of me!

AMERITRON AL-811: The AL-811 is a great amplifier and of current manufacture. The bands are 160 to 15 meters with an easy modification to extend coverage to the 10 meter band if not so equipped on the used market. The amplifier uses three inexpensive 811A triode tubes. The 811A tubes cost about $20 each. If the 811A becomes unavailable, three 572B tubes will directly replace the 811A. I mention this as Svetlana removed their 811A from manufacture due to not wanting to market a low profit tube. The 811A plate is much more fragile than the 572B, just pay attention during tune up. I have seen holes burned thru 811A plates, however the tubes still produced good power output! Approximately 70 watts input will produce 500 to 550 Watts SSB PEP. Tuned input provides a good SWR match for your solid-state HF transceiver. 120 VAC distribution will operate the amplifier. The keying circuit is low voltage for all except the IC-706 series of radios that are current and voltage restricted. Two meters measure HV, plate & grid current. The amplifier also has ALC control. Size is approximately 14.5"w x 8.5"h x 15"d (no advertised spec listed). I have found these amplifiers as low as $350 used in good condition. A real bargain with fresh electronics and parts.

Gonset GSB-201: This older 1960s amplifier operates on 80 to meters. Using four (4) 811A tubes, 100 watts input will produce approximately 700-800 Watts SSB PEP output. The meter measures plate current and relative power output. A front panel switch provides reduced output tuning and the power supply is of solid-state rectifier design. The keying circuit voltage is not known, an interface relay may be necessary. The amplifier did not specify tuned input, however four 811A tubes present a 75 ohm cathode input without any circuitry. Perhaps like the older Heathkit Warrier, a broadband design input is used to meet the Gonset advertised 50 ohm input. Size is 8.5"h x 12.63"w x 17"d. This amplifier is very heavy- watch shipping costs. Prices vary from about $250 to $350. Unlike the SB-200, this amplifier is rarely advertised for sale.

DENTRON CLIPPERTON L: This is a reliable 160 to 15 meter (modifable to 10 meters) amplifier. The amplifier uses four (4) rugged 572B tubes for 1100 Watts SSB PEP output with 100 watts input. Early models were without a tuned input. Four 572B tubes have a cathode input of 75 ohms without any circuitry. A real neat feature of this amplifier is a lower plate voltage 'CW' selection switch on the front panel. I have used four cheap 811A tubes with the 1800 VDC on the plates. DO NOT use the 2600 VDC SSB selection on 811A tubes. The output is 800 Watts SSB PEP with 100 Watts drive. As for higher than 811A specified voltage at 1500 VDC plate rating, the Collins 30L-1 applies 2000 VDC no signal dropping to approximately 1700 VDC at 700 Watts output. The amplifier has a single meter for plate & grid current. Low voltage antenna relay switching is used. Operation at 120 VAC is usable, however a 120 VAC 20 amp circuit is best. A cover on the rear panel provides an easy conversion to 240 VAC operation using simple jumpers. I do not have an exact size specification, the amplifier is rather compact at approximately 6"h x 15"w x 15"d. The lowest price is about $375, but this is the only easily obtainable amplifier in the 1KW+ output range.

HUNTER BANDIT 2000B: The Hunter Bandit 2000B is simular to the Dentron Clipperton L. Using four 572B tubes, this amplifier will also produce 1KW output with 100 Watts drive. The amplifier has two meters, one for relative output and the other for plate & grid current. The RF output meter is interesting in that adjustments for different feedline impedances and sensitivity adjustment on all bands has been engineered in the metering circuit. The amplifier does not have a selectable tuned input, however with four cathode tubes the specifications state 50 to 75 ohm input. Like the Clipperton L, 120 VAC operation is available. I would prefer the Clipperton L, but a Hunter Bandit at $300 would be interesting. Size appears simular to a SB-200.

Collins 30L-1: This collectors item is over budget for this article.

YAESU FL-2100B: I do not highly recommend this HF amplifier as arcing is somewhat common on the band switch and the amplifier operates somewhat hot. Perhaps it is a matter of improper tuning or a part upgrade eliminated the issue. With plenty of SB-200s available and usually at better prices, the FL-2100B is not my first choice.

AMP SUPPLY LA-1000, DENTRON GLA-1000: I do not recommend these amplifiers as replacement 6LQ6 or 6MJ6 'TV type' tubes cost about $40 to $50 each. The amplifiers use four tubes and power output is about 400 Watts SSB PEP.

GALAXY 2000, SBE SB2-LA: The Galaxy uses ten (10) 6HF5 TV type tubes and the SBE uses six (6) 6JE6 or 6LQ6 TV type tubes. As with the LA-1000 and GLA-1000, the tubes are very expensive unless your uncle has an old TV shop with NOS tubes. Sell the NOS tubes and buy a high-end amp!

HEATHKIT HA-14 'KW KOMPACT': This amplifier is simular to the SB-200 in that most of the circuitry including a tuned input is available. The tubes used are a pair of 572B. The title 'Kompact' is that the amplifier makes use of a remote power supply that looks and measures size wise like a HP-23 AC series power supply. A DC power supply is available, however I bet the switching transistors squeal like heavy equipment back-up alarms! The amplifier is reliable, however be very CAREFUL with the high voltage cable that travels from the remote power supply to the amplifier. The cable may have poor insulation due to age. The amplifier is only 3.375"h x 12.5"w x 10"d. Plate operating voltage is approximately 200 volts lower resulting in about 500 to 600 Watts SSB PEP output. Prices vary widely, however $300 to $350 with a 120 vac power supply is available on the used market. Much more rare than a SB-200, collectors may cause the price to rise.

This list of amplifiers is about all that is available on a budget. 3-500Z equipped Ameritron, Drake, Kenwood, Heathkit, Henry, AMP Supply and other amplifiers using ceramic tubes are way above the budget limit of this article. So, who cares if the 1500 watt amplifier produces approximately 1/2 to 3/4 an 'S' unit less on the receive side. The above bargains will provide a respectable signal. Good luck.

Member Comments:
This article has expired. No more comments may be added.
 
Help, I Need a Cheap HF Amplifier!  
by WA4DOU on August 21, 2002 Mail this to a friend!
Personally I believe you'll get more bang for your buck if you spend your time and money in the antenna system. And if you're not working all the dx you want, learn and use cw.
 
Help, I Need a Cheap HF Amplifier!  
by KG6AMW on August 21, 2002 Mail this to a friend!
With regards to Ameritron amp, replacing the 811 tube with the 572 is essentially a waste money. You won't put out anymore power and the 572 costs 3 times as much as the 811. Do the math and save your money.
 
RE: Help, I Need a Cheap HF Amplifier!  
by N8FVJ on August 21, 2002 Mail this to a friend!
Read the article. A beam antenna may not be enough. A beam antenna should come first unless 20 to 10 meters is unimportant. Of course, 572B is a waste of money right now, however, like the article stated, if the source of 811A tubes dries up (Svetlana, for example), a 572B is a drop-in replacement. I plan to keep my SB-200 a long time.
 
Help, I Need a Cheap HF Amplifier!  
by KG6AMW on August 21, 2002 Mail this to a friend!
Jim, nice article. I'm guessing that Russian company is no longer making the 572B. They may have a pretty decent size inventory left, but both the 811 and 572B are now made in China under a varity of names with all other brands (non China) consisting of recent inventory or NOS. Lets hope the Chinese stay in the glass business.
 
RE: Help, I Need a Cheap HF Amplifier!  
by W8MW on August 21, 2002 Mail this to a friend!
Jim: Very good info. Threads about amplifiers invariably include remarks about putting the money and effort into antennas instead. That advice is well-meaning but it presumes that you can only choose one or the other. How about both? A good antenna system plus an amplifier equals a high performance amateur radio station. Even a modest HF amp like the ones described here can make a big difference under certain operating conditions.

73, Mike W8MW
 
Help, I Need a Cheap HF Amplifier!  
by KE5V on August 21, 2002 Mail this to a friend!
Nice article. I've considered buying an HF amp but can't justify the cost or the space those things seem to take up. Seems like most stations I hear on 20m these days use amps. What I do not understand is why the current transceivers do not have greater power output. 100 watts seems to be the norm, except for a few Yaesu's. Seems strange that they can get 75 watts out of a small IC-V8000 2m, but the manufacturers chose to limit most of their HF rigs to 100 watts. Don't know why they don't bump that up to 300-500 watts, solid state. Size shouldn't be a factor, considering the wasted space I see inside most HF boxes. Heat? Don't think so, not if they use solid state. I'm looking forward to the day I can buy a nice basic Kenwood 570, Yaesu FT 840, or Icom 718 with 500 watt output. I can dream, can't I?
 
RE: Help, I Need a Cheap HF Amplifier!  
by KE4MOB on August 21, 2002 Mail this to a friend!
Nice article with a good overview of entry level amps. You mention the Dentron GLA-1000. A modification is available to use the Svetlana EL509 in place of the original 6LQ6's--matched quads run $100, and are still in production by the Russians. The application notes are available at:

http://www.svetlana.com/docs/TechBulletins/technoteNO.32.html

So if you find an old GLA-1000 in decent shape at a giveaway price, this might be an option.

Again, nice work.

Steve, KE4MOB

 
Help, I Need a Cheap HF Amplifier!  
by N9AB on August 21, 2002 Mail this to a friend!
Please do not buy a “cheap HF amplifier” and then overdrive it to achieve higher (more competitive) power output. Amplifiers should increase the SSB amplitude, and not increase the occupied bandwidth of the signal. Be especially cautious of any amplifier which uses 811-A tubes. These tubes are rated at ONLY 65 watts of plate dissipation. Replacing them with 572B’s is highly encouraged. Ideally, if you don’t need the full legal limit, you may still want to spend the extra dollars for a legal limit amplifier and simply run the exciter and amplifier at a lower conservative level.
 
RE: Help, I Need a Cheap HF Amplifier!  
by WA4DOU on August 21, 2002 Mail this to a friend!
My advice that one spend their effort and money in the antenna dept. does not presume that you can either do it there OR in an amplifier. It presumes that the greatest bang for the buck is in the antenna because you have to be able to hear them before you can work them. Listen to the pileups. There are often thousands of stations that can be heard but can't quite hear the dx.
 
Help, I Need a Cheap HF Amplifier!  
by K8DIT on August 21, 2002 Mail this to a friend!
Do I need an amp? Refusal, Denial, Anger and finally acceptance. Yes, I need an amp. I want an amp. An amp would be a good thing. Now, what do I know about the guys with amps? Go ask a ham with an amp. As in all things, you get what you pay for. Yeah, I used to have the SB-200, and then a couple of sweep tube amps, but then I found the (insert favorite amp brand here) that cost only (enter the diff. here) more than the other and now if I need a little power, I got it, and if I need more, I've got that too. It sure helps out the old timers hear me. It aslo is great for those times on 20 when I have to absolutely get my message through.
It's nice to be on the radio, when ordinarily I wouldve had to shut down due to conditions. The friend out on vacation has a mobile running 100 watts and I can hear him, but with that mobile whip, he just cannot hear me. If I had a few more db. he'd be able to hear me and complete his telling of whatever story he is able to share, knowing I can respond in kind.
Some guys wear an amplifier like a badge of honor, while some use it to crush the competition. Presuming you are just an ordinary ham who wants the tools to get the job done, pick an amp that complements your
hamming needs. Yes, itll spend most of its time off.
When you need it, its ready to go.
 
Help, I Need a Cheap HF Amplifier!  
by N4MVL on August 21, 2002 Mail this to a friend!
I have to agree with two points - 1) given the choice between an amplifier and a better antenna, go with the antenna so you can hear them, and 2) drop the 572Bs in your 811A amp AFTER you burn up an 811A, because the 572Bs can tolerate much more abuse. Good article!

73 de N4MVL

Lee

 
Help, I Need a Cheap HF Amplifier!  
by W4CNG on August 21, 2002 Mail this to a friend!
Very good article. After the best antenna you can put up, the next step is the getting to the 500 watt power level. That is your best bang for the buck, and there are lots of good bangs in this article. I'm limited to Attic Antennas, so my immediate next purchase was to increase Output power. As to taking solid state rigs into the 300-400 watt level, you increase the DC Current requirement into the 80-100Amp level. It is a little pricy to get 80-100amps at 12VDC whether bought or home brewed. Tubes on 120VAC are the most economical way to get there.
 
RE: Help, I Need a Cheap HF Amplifier!  
by WA4DOU on August 21, 2002 Mail this to a friend!
Some 811's are only rated at 45 watts, it might be the Chinese ones. 3 tubes under those conditions would add up to 135 watts, total plate dissipation. 4 would add up to 180 watts. At a plate efficiency of 65% it would be wise and prudent to only run 300 watts out with the 3 tube models and 400 watts out with the 4 tube models.
IF the 811's in your amp are rated at 65 watts then the combined plate dissipation would be 260 watts and it would be reasonable to run them at 500-550 watts output. Wouldn't it make more sense to run them conservatively and make them last? Do you really need that extra db or 2?
 
RE: Help, I Need a Cheap HF Amplifier!  
by WA4DOU on August 21, 2002 Mail this to a friend!
Some 811's are only rated at 45 watts, it might be the Chinese ones. 3 tubes under those conditions would add up to 135 watts, total plate dissipation. 4 would add up to 180 watts. At a plate efficiency of 65% it would be wise and prudent to only run 300 watts out with the 3 tube models and 400 watts out with the 4 tube models.
IF the 811's in your amp are rated at 65 watts then the combined plate dissipation would be 195 watts for the 3 tube models and 260 watts for the 4 tube models, thus permitting about 400 watts out and 500-550 watts out respectively while remaining within reasonable limits. Wouldn't it make more sense to run them conservatively than press for 1 or 2 db more at the expense of short tube life?
 
RE: Help, I Need a Cheap HF Amplifier!  
by N8FVJ on August 21, 2002 Mail this to a friend!
Correct me if I am wrong, the 811A plate dissipation ratings are 45 watts CCS and 65 watts ICAS. The 65 watts rating is fine on CW & SSB service. The plates can operate a dull red. The thoriated tungston filament is resilient as well- 25 watts filament power! I have viewed four 811A operating at 800 watts PEP output at 1800 VDC on the plates.
 
Help, I Need a Cheap HF Amplifier!  
by N6AJR on August 21, 2002 Mail this to a friend!
I currently own a Clipperton L, 2 Ameritron 811's, a home brew with 4 6lq6sweep tubes, a ameritron 500 watt (mobile) solid state amp, a couple of 300 watt amps by RM of italy and a 600 watt amp by RM of itally (mobile.).

I usuall use the 500 watt ameritron off a 70 amp astron power supply as my "normal" amp. I use the clipperton L when I need a bit more push (on 110v I get about 900 watts). I use the 600 watt RM in my pickup because it has rf sensing and I am running a yaesu FT 840 as a rig and it won't key the amp otherwise. There is no "keyed" output on the ft-840, they used to make a box that plugged into the 7 pin mini din plug, but they don't make the adaptor box any more. Be sure if you buy a rig It has the ability to key and amp. They never told me this when I bot the FT 840 new for almost $700.

I keep an eye on Ebay, and pick up amps Cheap when I see them. I bought one of my 811 amps new at $659 plus tax, the other I got on ebay for $300 plus $25 to ship. I have probably 5 or more 100 watt amps I use with converted cb's on 10 meters, and a bunch of 2 meter and 440 amps too. They run from 30 to 300 watts.

The trick is to keep an eye on ebay every day, have a couple extra bucks available to get a good deal with, and don't be afraid to look after midnite, thats when I usually get my best deals.... if they say " I have no way to test this" it means its broke, if they say " I plugged it in and the lights are on and I can't check it any further" then the lights come on but its still broke.

If they say it works but sold as is, then it probably works and is sold as is due to the the problem that folks will plug 12 volt rigs into 110 and then want their money back cause it broke. I have had good luck on Ebay, better luck than I have had at Hamfest's , but I buy used stuff from HRO too. I usually end up paying between 50 cents and a dollar a watt, used, double that if new. I don't reccommend putting 572's into the 811 amp, you are just wasting your money, and the 811 won't last in an amp designed for 572's. I have also had sbe 33's and sbe 34's , la 1000 nt (no tune) and several others. They all work, and ya' need to keep an eye open for a deal.

If you can't put up more antenna, then you will probably need an amp at some time or other. If you are NET CONTROL for some net its nice if you run a bit of power so everyone can hear you. 500 watt is probably my reccomendation, it will get you up out of the noise level but it doesn't make every light in the house dim. 73 and good luck tom N6AJR
 
Help, I Need a Cheap HF Amplifier!  
by N6AJR on August 21, 2002 Mail this to a friend!
I currently own a Clipperton L, 2 Ameritron 811's, a home brew with 4 6lq6sweep tubes, a ameritron 500 watt (mobile) solid state amp, a couple of 300 watt amps by RM of italy and a 600 watt amp by RM of itally (mobile.).

I usuall use the 500 watt ameritron off a 70 amp astron power supply as my "normal" amp. I use the clipperton L when I need a bit more push (on 110v I get about 900 watts). I use the 600 watt RM in my pickup because it has rf sensing and I am running a yaesu FT 840 as a rig and it won't key the amp otherwise. There is no "keyed" output on the ft-840, they used to make a box that plugged into the 7 pin mini din plug, but they don't make the adaptor box any more. Be sure if you buy a rig It has the ability to key and amp. They never told me this when I bot the FT 840 new for almost $700.

I keep an eye on Ebay, and pick up amps Cheap when I see them. I bought one of my 811 amps new at $659 plus tax, the other I got on ebay for $300 plus $25 to ship. I have probably 5 or more 100 watt amps I use with converted cb's on 10 meters, and a bunch of 2 meter and 440 amps too. They run from 30 to 300 watts.

The trick is to keep an eye on ebay every day, have a couple extra bucks available to get a good deal with, and don't be afraid to look after midnite, thats when I usually get my best deals.... if they say " I have no way to test this" it means its broke, if they say " I plugged it in and the lights are on and I can't check it any further" then the lights come on but its still broke.

If they say it works but sold as is, then it probably works and is sold as is due to the the problem that folks will plug 12 volt rigs into 110 and then want their money back cause it broke. I have had good luck on Ebay, better luck than I have had at Hamfest's , but I buy used stuff from HRO too. I usually end up paying between 50 cents and a dollar a watt, used, double that if new. I don't reccommend putting 572's into the 811 amp, you are just wasting your money, and the 811 won't last in an amp designed for 572's. I have also had sbe 33's and sbe 34's , la 1000 nt (no tune) and several others. They all work, and ya' need to keep an eye open for a deal.

If you can't put up more antenna, then you will probably need an amp at some time or other. If you are NET CONTROL for some net its nice if you run a bit of power so everyone can hear you. 500 watt is probably my reccomendation, it will get you up out of the noise level but it doesn't make every light in the house dim. 73 and good luck tom N6AJR
 
Help, I Need a Cheap HF Amplifier!  
by VK5CC on August 21, 2002 Mail this to a friend!
A good article however the collins 30L1 is still the best 811a amp on the market today.It will do 500w all day long, is super clean with a third order imd around 36db, built to mil spec and can be purchased for 500usd which is great value for a classic piece of vintage gear. If 811a's are operated within spec they will last for years. My 811a's in my 30L1 are dated 1950 and still put out 800w key down!But money spent on the antenna is much better value even if it means buying bigger masts to hold dipoles up higher or using a phasing network to phase verticals etc. Increasing power without increasing antenna performance will only make you an aligator--all mouth and no ears!!

YOU CANT WORK EM IF YOU CAN'T EAR EM!!

BEST 73.
 
RE: Help, I Need a Cheap HF Amplifier!  
by N8FVJ on August 21, 2002 Mail this to a friend!
I noticed on 75 meters at evening hours I hear about every SSB station on a simple dipole antenna- 'I can hear them, just can not work them' is the issue. Problem is the signal output from a station is barely above the band noise at 100 watts SSB PEP output. Although the winter months are far better, not everyone wants to be a seasonal operator on 75 meters SSB. I know a simple, low cost amplifier makes a necessary difference under these conditions. The band requires a few 'S' units increase on the other end. Thus, this is not a weak signal mode, it is a band noise issue. I believe the amplifier is a low cost solution in this application.
 
RE: Help, I Need a Cheap HF Amplifier!  
by N3HKN on August 21, 2002 Mail this to a friend!
Good stuff! For new amps I believe that the max you should pay is $1,00 per watt. Amertiron 811 series fits this well. A used unit should be about 1/2 due to inability to assess the remaining life of the tubes.

Then, why go higher than 500-800 watts. Do the simple percentages.

Double your 750 watt amp to 1500 watts. Double or more the price to at least $2000.
Now just look at what you shpuld have done. For $800 new you can increase your power by "8" times. Now since you flunked math but have money to burn you spend say another $1200 to ONLY DOUBLE your power. That simply does not make sense. Most Hams will never grasp this and stumble onward wasting money and electrical power. Ameritron has the sweet spot with their 811A and 572 amps!!!
Dick N3HKN
 
Help, I Need a Cheap HF Amplifier!  
by VK5CC on August 21, 2002 Mail this to a friend!
TO N8FVJ: Argue for your limitations and you will get to keep them. If you read your last comments carefully you will find the solution. The amplifier is one solution but not the best one. If you can hear them but they can't hear you through the noise then its the antenna primarily that is the problem. Think about solutions to improving your antenna and you won't need the amp for local ragchewing even in noisy conditions.There are many simple antenna solutions to help you increase your signal strength that don't need an Amp.

Cheers from Chris.
 
RE: Help, I Need a Cheap HF Amplifier!  
by N8FVJ on August 21, 2002 Mail this to a friend!
For the sake of my comment, at risk of not being 'a player', I offer the following: A dipole antenna is the most prevalent antenna on 75 meters SSB. Most amateurs can not elevate a dipole antenna to 80-100 feet, and most not for $300. For the best signal in all directions, two dipoles are required. A directional rhomic is not a inexpensive option and most do not have the property. A phase array of four verticals are again, not cheap. A directional beam is not inexpensive either. A full wave loop also is not the best solution, however a great antenna if property is available. Ever hear of a beverage antenna. Excellent for 75 meters receive during high band noise levels, terrible gain- HI! An amplifier is the most cost effective solution for most amateurs.
 
RE: Help, I Need a Cheap HF Amplifier!  
by K1OU on August 21, 2002 Mail this to a friend!
One of the best articles I have seen in a long time.

I did the 572B drop-in when I had an AL811. Combined with a delta loop up about fifty feet, I had no problem swatting flies on 75.

It is all about common sense. A good amount of RF combined with a good antenna makes you louder than somebody running an Alpha into a store-bought trap dipole.
 
Help, I Need a Cheap HF Amplifier!  
by KD6NXI on August 21, 2002 Mail this to a friend!
No what you need is to improve your antenna system or receiver. All an amplifier will do is increase the noise on already noisy bands. I've often thought that anyone who wants an amp should have to homebrew their own. I did, tried it a few times,, determined that it was a fine accomplishment, then put it in the garage and there it sits.

With all due respect you sort of sound like a recent cb'er who never got over the childish fascination with amplifiers....
 
RE: Help, I Need a Cheap HF Amplifier!  
by N8FVJ on August 21, 2002 Mail this to a friend!
Gentlemen, the article is not a request to evaluate my antenna system with regard to having a problem. I recommend using the 'elmer' section on this site for troubleshooting. My antenna system is good by most standards. I have a 3 element five bander that covers 20 to 10 meters. I have four elements on 6 meters and all antennas are at 1500 feet elevation with a view of 300 degrees as far as one can see. My full wave loop is for 80 & 40 meters. Without reservation, 600 watts into any of my antennas will simply outperform 100 watts. I do not use an amplifier when it is not needed. Aurora 6 meter work requires a strong signal, this operation is not a low power mode of operation. The difference on 75 meters is good reports vs 'very difficult to copy' or no copy. Obviously, some of you have not much experience on 75 meters under noisy band conditions. In the south, the band is even more noisy as I operated there as well. For difficult contacts half way around the world, the extra power is the difference between a successful contact and no contact- been there, done that! As for amplifier design, I can design HF RF amps with ease. Studied Richard Measures notes as well on amplifier design. If you prefer not to own an amplifier or to operate QRP, fine. Please do not impose your will on the group of us that prefer amplifier use when required. Ham operators that use 600 watt amplifiers are not of the abusive, CBer mentality suggested. I believe our comments should be an aid to newer hams and hams who have not experienced an amplifier. That is the intent of the article. For the group reading this article with interest, I am well versed in amplifier design and use.
 
RE: Help, I Need a Cheap HF Amplifier!  
by N8FVJ on August 21, 2002 Mail this to a friend!
Mr. Dan Cox, I suggest you read my articles on transceivers on this site over the last 15 months. The articles focus on receiver performance. I am well versed on receiver design and performance. I do not have any receiver performance issues, your comment does not apply in anyway to the accuracy of my obversations regarding amplifier use.
 
Help, I Need a Cheap HF Amplifier!  
by W8CQ on August 21, 2002 Mail this to a friend!
Hi Jim,
Nice article. Just one correction to point out for reference. The SB-200 has -120VDC on the keying line, not +120VDC.

73,
Jeff Weinberg W8CQ
Harbach Electronics
 
RE: Help, I Need a Cheap HF Amplifier!  
by N8FVJ on August 22, 2002 Mail this to a friend!
Thanks Jeff. Always considered cutoff bias to be negative, never positive, thus did not use either a + or - sign. Only positive bias I ever seen was using an 833A in Class A, single-ended as an audio tube with low plate voltage. Cutoff bias does not apply here.
 
Help, I Need a Cheap HF Amplifier!  
by K4JJL on August 22, 2002 Mail this to a friend!
I picked up a Heathkit SB-1000 (same thing as Ameritron AL-80A) for $400 at a hamfest. It obviously was not used much because there wasn't the first speck of dust inside. Definitely not trashed. Uses 1 3-500Z tube and I get about 1100 watts out on good days.
 
RE: Help, I Need a Cheap HF Amplifier!  
by KD6NXI on August 22, 2002 Mail this to a friend!
I've communicated with Australia on 75,, with a tube type ranger transmitter and drifty old tube receiver(don't recall model,, maybe s53a) running around 50 watts...on AM.. You don't need to run "CB mode" to "Get out" 10-4?
 
RE: Help, I Need a Cheap HF Amplifier!  
by WB2WIK on August 22, 2002 Mail this to a friend!
Nice article and chat.

Those interested in "best buy" bargains for good amps would be well advised to keep their eyes peeled for older 3-500Z amps at flea markets and swap meets (and NOT on eBay)...

At the TRW Swap Meet in southern California, only last month there was a mint condition Swan Mark II (pair of 3-500Z's, easily capable of 1200W PEP output conservatively) that got snapped up for $400. I sold my old Johnson Thunderbolt (pair of 4-400A's runs about 1kW PEP output conservatively) a few years back for only $350 simply because the buyer really wanted it, and I really got tired of having such a back breaker (it weighs 140 lbs). Deals like this abound, but I don't see them on eBay. I wouldn't buy a 140 lb amplifier that had to be shipped, even if it were free.

Go to the swap meets!

73 de Steve, WB2WIK/6
 
Help, I Need a Cheap HF Amplifier!  
by KE3HO on August 22, 2002 Mail this to a friend!
Nice article, Jim. I have heard the "If you can't hear them, you can't work them" comments from people who would suggest spending the money on the antenna system. This is good advise if you can do it. Having a station that is "all mouth and no ears" is no good to anyone (except maybe talking to other similar stations). However, that does not mean that there is no place for the amplifier in the ham shack. Yes, on the upper HF bands you would be better off with a 5 element beam on top of a tall tower. But this says nothing about the lower bands. How many people can put up a 5 element beam for 80M (and at a height where it can actually perform like a 5 element antenna)? Not me. Not most hams. I can't even put up a 2 element beam for 80M. For 80M I have an inverted V with the apex up at about 70 feet. I am lucky to have a large enough yard with a very well placed tall tree. Not everyone can even put up an antenna like this. There are times when the amplifier comes in handy, and those are the times when it should be used. I know hams who go into their shack and turn on the amp and the rig at the same time and run 1kw at all times. They shouldn't do that. That is not what Jim is supporting. Yes, a better antenna is a better solution on paper, but the reality is that there are times when the amp is necessary. One should always start with the best antenna possible for your circumstances. Then use the amp only when necessary. Jim has done a good job of pointing out some of the most cost effective options out there. Nice job.

73,
Jim
 
RE: Help, I Need a Cheap HF Amplifier!  
by N0TONE on August 22, 2002 Mail this to a friend!
Yes and no...

At the start of the article, Jim says that on 75 meters, chances are your buddies can't or aren't willing to hear you. I have a major problem with this. If it's true that on 100 watts, your signal is so weak that it's inaudible, then on 600 watts, your signal will be competing with noise, and still won't be armchair copy.

I do use an amp, but as others have said, you need to make sure the antenna is the best you can do in your circumstances. No, I do not immediately say "go work on your antenna first". Fact is, due to a variety of circumstances mainly associates with lot size, CC&Rs or finite budget, it is very possible to have the "best" antenna you can have, particularly on 80 meters or lower frequencies.

Also remember what 160, 80 and 40 are like. The static crashes and other atmospheric noise on those bands are so loud that your antenna can lose 20dB and you can still hear it all. A better antenna on those bands often does not help you hear whatsoever - so it really becomes an issue of tranmit ability not receiving. Those of us operating 160 and 80 for DXing are fully aware of this because we intentionally use very lossy receive antennas, using the ability to null signals as the only way to improve reception.

N8FVJ confesses that he uses a horizontal loop on 40 and 80. If that loop isn't very high, then more than half the power is going straight up and straight down. I'm assuming it's a one wavelength or shorter loop. Any number of NEC analyses have shown that a half wave, or even a shortened, linearly loaded diple, at the same height as a one wavelength loop, sends more of its power the "intended" direction.

To test your 75 meter antenna's effectiveness, make some QSOs on 75 meter phone using 100 watts. If NOBODY hears you, then you need to work on the antenna. If you can make QSOs but the reports suggest that your signal is "copyable" but not very strong, then you can probably improve the antenna, if you have the space, ability to raise it, or money.

Some have said you need two dipoles in order to cover every direction. I dare say this is false for anybody who finds this discussion interesting. Use NEC to check for yourself: an 80 meter dipole at only 50 feet off the ground, at a useful radiation angle of between 10 and 30 degrees, is non-directional. You do not need two dipoles unless you have them at least 3/8 wave off the ground. And, if you really can get that much height (and are using GOOD feedline - RG8 is no good when the run is long, even on 75 meters), then you probably don't need an amp.

BTW, these comments are directed towards the idea of local SSB ragchews. Things are different for DXing, very different.

So, please DO make sure your antenna is the best you can muster given your particular set of restrictions.

My own 75 meter situation is a linearly loaded wire antenna at 65 feet. Almost free, it's held up by indigeonous trees. Only 55 feet in overall length, I made it resonant by adding more wire on each end, folding it back and forth until I achieved resonance at about 3.55 MHz (I'm mostly a CW op, so I tuned for CW). I had it fed with RG-8, about 100 feet of it. On CW, things worked great. I heard well, including most DX that was spotted on the 'net, and on 100 watts, I could work almost anybody I could hear. For DX, I frequently did turn on the amp. But the story up on 75 meter SSB was different. SWR rose to about 4:1. Atmospheric noise was notably quieter, even if I tuned it with a well-designed tuner. There seemed to be a fair number of stations that I could hear well, who could not hear me at all. Something was amiss. I was convinced to switch out the RG-8 to open wire line. I first used ladder line, with good results, but during the rainy season it got lossy, so I homebrewed some open wire and it's doing better. I now have to use the tuner on all frequencies, but my results on CW (if I can hear them, I can work them 90%of the time with 100 watts) were now duplicated on 75 SSB. That's with an antenna less than 1/4 wave long. For me, the trick was the open wire, and the height doesn't hurt. BTW, this antenna's radiation pattern "should be" north-south, but I have equal results all directions.

For amplifiers, my own recommendation is to purchase an SB-200 in semi-hulk mode. As long as it has "useful" tubes and a good HV transformer, it's worth considering. You can get semi-hulks for $100-$150 from CBers who don't know what they're doing. If the amp's been abused, the components that are most likely bad are the three 33 ohm 1 watt carbon composition resistors underneath the tube sockets. Replacements are easily available and take 20 minutes to intall, and no re-tuning is required.

The Heath-supplied input networks are never tuned right, and typical input SWR is 3:1. Spray a touch of silicone lube into each inductor, and use a plastic hex tool to tune. Some bands won't do better than 2:1 but that's better than 3:1.

I've helped quite a few guys get these semi-hulks on the air. If the tubes will light up at all, I've always been able to get 600 watts output with 100 watts of drive. If the tubes are good, then it'll still be 600 watts out, but the drive will be more like 50 watts.

The "suppressors" - the 2 watt resistors with wire wound around them, connected to the plates - seem to be almost irrelevant. I think the inductor does most of the "work" because I've had amplifiers where those resistors were charred black, or burned clean in two, and the amps worked, and did not oscillate. One anp with a clearly homebrew set of suppressors (the wire was not surrounding the resistor, but rather wound completely off the resistor and at right angles, and it had metal oxide resistors instead of carbon) refused to tame itself until I homebrewed stock style suppressors for it.

Searching the 'net shows that the Svetlana 572B tubes should be avoided. It seems that Svetlana's goal for the 572B tubes was audio - they make the tube with and without a plate cap. Audio nuts don't use the plate cap version. Audio amps use lower plate voltage. The RF-rated versions were audio tubes with a plate cap, and could not handle the higher plate voltages ham amps used. I've had excellent results with Chinese tubes, branded by National or others. But one caution, you only get 30 days warranty on the cheaper tubes. Sometimes they are DOA, so even if you're buying tubes only as spares, definitely pop them into the amp and make certain they work.

The FL-2100B looks like a poor clone of the SB-200, and I'd avoid it.

Most of the older amplifiers do use high voltages for keying. If you're on a budget, you might already be using tube type HF rigs, like the Collins or Drake. Those rigs use relay contacts to key the amps, so they're fine with the high voltage keying. But if you're using more modern gear, then you definitely have to look into a keying interface. Amplifers are a part of ham radio where a willingness to do a little homebrewing can save major dollars. Do a web search for "amplifier keying interface" and you'll find a number of sites with designs that can be built for $5 or so. Otherwise, you'll have to purchase such an interface for $50 or more.

QSK is possible, but you'll DEFINITELY be homebrewing your solution for it. Vacuum relays are $30 or more and the drive circuit timing is critical. So you'll have to build the QSK circuits, then use a good RF-capable scope to make sure you got the timing right. If you are otherwise an electronics geek, then you may have enough test equipment already, but if you're an appliance op who's just getting his feet wet in homebrewing, then QSK is not a good choice of projects. Yes, I have fitted many amps with QSK - I'm a CW hound, and consider QSK a requirement.

The other major absence in cheap amps is 160 meters, probably the only HF band where you really need power most of the time (unless you REALLY like just local chit-chat!). Again, it's a challenging project to add 160 to an existing amp, although you could sacrifice an existing band and make it a bit easier. In my case, I just bought another semi-hulk SB-200 and turned it into a monoband 160 meter amp.

I'm known as one of the local "amplifier" gurus (or nut-cases as is more accurate). So, I get lots of guys just giving me non-functional amps. I'm definitely a low-budget ham, but you wouldn't know it to look at my amplifier collection. But seriously, I may have as much as $100 total invested, since they mainly came to me as dead hulks. Overall, the SB-200 is the nicest of the amps I've worked on, if you want something easy to get used to, rugged enough for almost anything, light on the wallet and AC power requirements (120VAC is just fine) and small enough to not overload your operating desk. I have a couple of Alphas too, and while they are distinctly high end, they're not for someone who isn't ready to get serious about a 240VAC outlet, and an operating table that can take the weight.

Regarding the SB-220 - it's sort of a mixed bag. The power supply in the SB-220 is only a little bit bigger than the one in the SB-200. But with two 3-500Z tubes, hams do try to get 1.5kW from it. At that power level, the cooling system has no overhead and the power supply is really being pushed hard. You can get SB-220s in modest condition for $300-$350, and they'll need a full restoration of switches, etc. And most SB-220s have had inexpert mods done to them, which would need removal. The SB-220 runs much hotter than the SB-200.

Another way to look at the SB-200 versus the SB-220 is this: The SB-200, with its tubes rated for 320W of dissipation max, is a small amp with a power supply and cooling system that keeps things operating in an OK state. You CAN abuse it, but you have to work at it. Some hams refer to the SB-200 as a "puny" amp. Some would claim that the tubes are too small for the power supply, so you CAN cook a tube. The SB-220, though, has a power supply that is utterly incapable of cooking the tubes, and a cooling system that works, unless you push the amp to full power for any length of time. It's easier to abuse an SB-220 because the margins in it are much smaller. However, if you're mainly an SSB op who doesn't use a lot of compression, an SB-220 will be durable enough. The SB-220 is a bit harder to work on, particularly tuning the input networks, which requires removing the front panel and either fabricating a new one with the right holes, or exposing yourself to dangerous voltages.

Most SB-200s that come across my bench are in better condition than most SB-220s.

Amps are fun, but I do echo the sentiment of those who suggest getting the antenna right first. And you definitely need an amp if you're the sort who wants to work stations who are right at the noise level, and you're on 80 or 160 meters. Quite often, those DX signals that are barely audible are coming from stations who have several elements (wire beams on 80 are common) and an amp - and they WON'T hear you on your 100 watts and attic-mounted loop. But as I said before, DX is a different subject than ragchews!

73 and have fun,

AM
 
RE: Help, I Need a Cheap HF Amplifier!  
by W7UIV on August 22, 2002 Mail this to a friend!
Everybody knows "you can't work em if you can't hear em". But that isn't the problem Jim started this thread with. Read again and see. He asks; "Ever try 75 meter SSB early to mid evening with 100 watts? Chances are YOUR HAM BUD'S won't even hear YOU".

So now we tell him the solution is to put up a better antenna because; "you can't work em if you can't hear em"(?) But he can already hear em. He can hear em fine. The problem he is having is this; "you can't work em if they can't hear YOU".

We don't know the antenna but we assume it is something conventional as a dipole or inverted vee dipole, and it's already up the best he can do for that location. If not, it needs to be. But this alone probably won't be enough.

Someone said the best bang for the buck is a 500 watt amplifier. From several years of amplifier building and on-air tests at various power levels I concur with that.

The best bang for the buck is going to be had in the FIRST 500 watts. And as with many things over the long range it's not found in the cheapest, nor in the most expensive. Sweep tube amplifiers do the job and so do those with commercial grade tubes. But to me the 572B is the sweet spot. Either two or four of them, depending on whether one is going to be mostly ssb and cw, or wants to run at the same power level with RTTY.
 
RE: Help, I Need a Cheap HF Amplifier!  
by W5HTW on August 22, 2002 Mail this to a friend!
What a surprise to see the Hunter Bandit mentioned! It seems to be the "forgotten amp." It makes a great desktop kilowatt, with low-noise fans, and it loves 220VAC. It will run on 120 VAC but with heavy AC line, short runs, and heavy breakers. Mine has been kicking around for probably 35 years, and though it has quite a few cosmetic problems, it still does a fine job. I picked it up five years ago at a ham fest for $300, brought it home, plugged it into 120 VAC, turned it on, and it has always worked ever since. I did, though, switch it to 220 shortly afterward. What I really like about it, is the three-position power switch (mounted internally, so never, ever, ever reach in there without watching the voltage bleed off to zero and even then wait another couple of minutes!) I run mine on Low most of the time, which is 1800 VDC, and about 600 MA on Tune, which translates to a nice 450 watts output on SSB. Yeah, it will do a whole lot more power on Medium, or on High (plate voltage around 2500) but I don't drive my car at the speedometer peg either.

Then again, the amplifer is turned on about once a month just to let it sit and blow the moisture out. I'm like many of the others here - need a better signal? Try CW. 100 watts on CW will get just about any job done. With wire antennas, I seem to work those I need, so I guess it could be said I don't need much, or I don't know if I need much! In other words, it works, and I don't fix things that work (not any more -- been there, done that!)

Anyway, thanks for the mention of the Bandit. Great little amp. Puts out key down 1200 watts if I run additional cooling (external boxer fan, just lying on top, on bushings, pulling the air out) on high power, but I only try that once in a while to be sure it still has the ooomph. About the only time I ever use it is on a net where I may not be quite making it in with the 100 watts.

73
Ed


 
RE: Help, I Need a Cheap HF Amplifier!  
by W8CQ on August 22, 2002 Mail this to a friend!
Hi Jim,
The SB-220 does use +120VDC to bias the tubes off during stanby. During transmit, it use the zener diode (or string of diodes) to develope the bias for the resting plate current.

73,
Jeff W8CQ
 
RE: Help, I Need a Cheap HF Amplifier!  
by K3WA on August 22, 2002 Mail this to a friend!
For all the comments that talk about improving antennas instead of buying an amp... many of us live in areas with CCRs and/or don't have trees. For one reason or another, we're stuck with a basic antenna. An amp is a reasonable way to make us heard, if not competitive.

73... Bill K3WA
 
RE: Help, I Need a Cheap HF Amplifier!  
by WB2WIK on August 23, 2002 Mail this to a friend!
It is surely true than an amp is sometimes the only answer because the law of antenna reciprocity doesn't take into account some undeniable variables.

Example: Stations with huge antennas used for both TX/RX operations hear lots of noise that stations with smaller antennas do not. Yes, they get out great, but could be plagued with so much sun/lightning/other noise that unless a received signal is S9 (possibly 50 uV), they can't hear it. Now, a "little" station using a small, low-noise antenna like a magnetic loop, calls in with 100W. There's far more than an 11.7 dB disparity (the difference between the "big gun's" 1500W and the "little pistol's" 100W), because the little guy has an S0 noise level, and the big gun has an S9 noise level. That might be 50dB, not 11.7. Unless the little station runs 1500W output, there's little chance he'll be detected above the big station's noise level.

DSP and active noise cancellation techniques, and using low-noise RX-only antennas like Beverages and magnetic loops, help level the playing field -- but 50dB is a rather huge difference to make up, and most stations using 75 or 80m don't even have separate receiving antennas (most big contest stations do).

Unfortunately, for the same reasons that many "little pistol" stations don't have enormous antennas, they risk horrendous RFI problems when running high power. CC&R's often (not always) imply "close living," where neighbors are sharing the same building, or living in structures quite close to the amateur. This can be a recipe for disaster when the ham attempts to run QRO without regard for potential interference problems. But if he's careful, and escalates power slowly while monitoring appliances that might be RFI-prone, and solves each problem specifically before raising power more, it can be done. I ran 1500W output on 80 through 6 meters from a townhouse for 1-1/2 years, using stealth antennas...it's possible, but takes a serious investment in debugging the RFI problems.

WB2WIK/6
 
Help, I Need a Cheap HF Amplifier!  
by W9CW on August 23, 2002 Mail this to a friend!
I've owned several amps in the past 40 years, from very small homebrew amps to a Collins 30S1. But, I prefer the smaller amps such as the Heathkit SB-200 or the Collins 30L1. Don't discount the 30L1, as it can be had for a reasonable price and has wonderful engineering and build-quality. Yes, the antenna debate always raises its ugly head when discussing amps, but not everyone has the space these days for antenna farms. In fact, it's difficult for some of us to get up a dipole on 80 meters! Thus, one sometimes has to work with what's available. And, this is the paradox: when living in a typical subdivison or on a city lot, antenna space is generally quite limited, but then again, lighting off an amp to compensate for the marginal antenna system can create havoc with neighbors with TVI or BCI problems. Maybe this explains the tremendous resurgence in QRP operation today. But, here again, this places even more demands on the antenna system.

An excellent article, with viable information on all of the listed amps, especially the Hunter Bandit - real workhorse! Buy a SB-200 and install the Harbach mods -- keying, soft-start, power supply board, etc. --(if still available due to the death of Mr. Harbach) and you will have a cost-effective and rugged amp which does the job well for the "average" operator.

73,
Don Allen W9CW
 
Help, I Need a Cheap HF Amplifier!  
by K9KJP on August 23, 2002 Mail this to a friend!
Good article, the amp/antenna debate has been beat to death many times. I used to operate 75m quite a bit, unless you are part of a 'group' you can pretty much forget 100watts in the summer unless you have one heck of an antenna. I recently moved to a restricted subdivision and I have tried several hidden, folded, loaded dipoles and have had -0- luck with 100 watts. Sure it would be nice to have a 200' ladder line fed dipole at 60' but thats not going to happen here :( I have a full length 75m coax fed inverted V thats about 50' in the center and while it works, 100 watts (even 500) with the static crashes on 75m makes me repeat myself way too many times for comfort. Its fine for hit and run contacts if thats what you are into..

Its nice to sit back with a couple acres and say 'well son you CBers need a better antenna instead of an amp' but an amp is a fact of life for most on 160 and 75 in the summer if you want a decent conversation that lasts more then 45 seconds - unless you are talking to your neighbor.

People are worried about splatter from overdriving small amps, no worst then a guy with his speech compressor cranked to the max and his 'tweaked' output to 150 watts because he has to (or thinks he has to) do it to get heard.

I challenge anyone to come to my house and build an antenna that will get me heard comfortably to the upper midwest on 75m in the summer with 100watts that the antenna police wont see - in the meantime I'll just run an amp and wont be holding my breath...

BTW, the FL2100 isnt a bad amp, isnt as heavy duty as a SB200 and a bear to work on but they work well if tuned carefully and the plate choke/suppressors havent been melted away by a CBer. Plus its not green and its quiet :)

Also be careful of amps like most dentrons and older amps without a tuned input, although they can be used with an internal tuner going 'straight in' with a solid state rig usually doesnt work well. Your signal will not be as clean w/o the 'flywheel' effect of a tuned input but how much that makes in reality a difference is debatable..

Also most older amps are going to be needing filter caps and other minor work and do not include 160m or the warc bands. Best bang for the buck is the AL-80A/B or AL-811H, yes they cost a couple hundred more then a SB200 or clipperton but they are fairly new and will be plug and play with newer tranceivers. I recently bought an AL-811 for 300.00 - I could have swore it was new, not a powerhouse but a nice little amp.

Dont forget the little Henry 1KD5 (1x3-500), its usually cheap (assembled offshore) and is a GREAT little amp if you dont need 160. Last one I bought for 400.00, very well made.. The amp supply LA-450 single 3-500 is another decent 'cheap' amp.
 
RE: Help, I Need a Cheap HF Amplifier!  
by N0TONE on August 23, 2002 Mail this to a friend!
There are always a few misperceptions that need to be reconciled on these threads.

To the ham who referred to "big" antennas as being noisier - that's not, strictly speaking, correct.

Under the normal 160, 80 and 40 meter conditions, the atmospheric noise comes in from virtually all compass directions. In that condition, if your 80 meter dipole is high enough to actually have any directivity, will you hear more noise, or less? The answer is - you'll hear the SAME amount of noise. If the antenna has directivity, then it has gain. So, let's say your 80 meter dipole exhibits 2dB gain in some direction at 100 feet high, compared with the same antenna at 30 feet. You will hear noise from that one direction (two directions, of course with a dipole), but you will hear less noise from the direction of the antenna nulls. This is always true for broadband, omnidirectional atmospheric noise.

I can't do so on my present lot, but I've often used wire beams on 40 and 80. Even if they're not erected very high (25 to 40 feet is workable), they produce dramatic improvements in RECEIVED signal to noise ratio. Because the signal I'm aiming at has grown by the gain of the antenna, yet the noise level stayed the same.

The other little thing about high versus low antennas is the angle of radiation, aka take-off angle. A low horizontal antenna has major lobes fairly high. A high antenna has major lobes fairly low. Depending on band, you may want one or the other. Realistically, on 80 meters, anybody with any limitations at all cannot possibly have too low of an angle of radiation - we can get the antennas that high. On 40, it's possible. From one of my west coast locations, I can erect a 40 meter dipole at either 60 feet or 20 feet. The dipole at 20 feet hears JA stations much better than the dipole at 60 feet. On 40 meters, JA stations come in at a surprisingly high angle.

40 meters, in fact, has an unusual characterist that favors low antennas. The major source of QRM in the US is foreign SW stations. If you erect a very low antenna - in my case a dipole at only 5 feet high - you kill the ability to receive low angle propagation. With a dipole 5 feet high, I hear the same amount of atmospheric noise as with a high dipole, but the foreign SW is reduced to that noise level. And I can hear the US hams quite well. Everything is down some, but the SW broadcasts are down the most. It's a poor TX antenna, but for that, I use my shortened dipole at 65 feet. I think every HF transceiver these days has a separate RX jack. So it's always worth experimenting with antennas.

I have a small lot, but no CC&Rs. I have built two-element end-loaded 80 meter beams. The results suggest that even in Yagi configuration, I successfully lowered the angles of radiation, even if they're only mounted 30 feet high. I've made them successful with element lengths and spacings roughly equal to a full size 20 meter beam. It can be done.

Some turn to verticals for low angle radiation. A vertical over good ground is vastly superior, for low angles, over almost any antenna that can be practically built for 40 and 80 meters. However, a vertical over bad ground, is inferior to almost anything you can name, except a dummy load. The whole equation changes with elevated-feed verticals which do seem to demonstrate useful efficiency even with no radials.

Again, I'm not anti-amplifier. But we can all do things with our antennas. I've been in three situations with heavy CC&Rs. One of them was a two-story house. I did my own landscaping, having purchased the house new. Before laying the sod, I rolled out chicken wire, bonded it all together and made sure it was available near the house. Then, later, I built a walk-out deck on the 2nd floor, coming from the master bedroom. That deck was built with 4 X 4 posts supporting it from ground level. Those 4 X 4 posts rose much higher than the deck. They not only supported a roof over the deck, but they protruded another full 8 feet over the roof. The total length of those 4 X 4 posts was 24 feet off the ground, and they were about the same distance apart. I ran #12 gauge brown-insulated wire up each one, used a little matching network at the base, fed against the buried chicken wire, and phased the two. I had a resounding signal into Europe, the direction this driven element was aimed. That was on 40 meters. I used it some on 20 meters also.

For contesting from that house, I had an attic-mounted loop, and an attic-mounted short dipole. I later added a loop snugged underneath the shingles on the roof; this one could comfortably tune 80 meters. Further loops populated the separate attic over the garage. For contesting, you want a lot of switchable antennas, not just one big high one.

In another CC&R restricted home, I had the glory of three-level tiered landscaping in the back. At the back of the property was a wood fence that ran along the neighborhood. An insulated wire, stapled to the back of that fence, facing the open field, running for some 1000 feet, did marvels on many low bands.

In the third CC&R restricted neighborhood, my house had a chimney for the fireplace on one end, and the other end was where the furnace vent was located. I strung a visible wire between the two, telling the neighbors that I wanted to put the Christmas lights up before the snow fell. This horizontal wire, because it was a two-story home, was at about 20 feet in height. I fed it with open-wire line down the back of the house, and handled the lousy SWR with a tuner. It was about 45 feet long, going from one end of the roof to the other. On 75 SSB I never felt the need for an amplifier with it. Had I used coax, I'd have been dead meat.

For antennas, it comes down to this. If it's not working well enough to be heard on 100 watts, change it. Do anything to it. If it's a flat top dipole, add 10 feet to each and and let them hang down. Or move the feedpoint 10 to 20 feet off center, maybe it will tune better. If it's not resonance, and provides a poor SWR, get any form of non-coax line in there. Standard 300 ohm TV twinlead can handle full power, and has far less loss than RG-8 and costs less, and neighbors are less likely to object to it, since they know what twinlead is for. If you are forced by circumstances to use a vertical, then some radials are better than none. If you can only use a few radials, they are better (MUCH better) if elevated. If you cannot use any radials at all, then center-feed the vertical. That's a good idea anyway unless you can have a solid metal sheet for ground.

I know one ham whose condominium is a one floor unit. The adjoining unit is two stories. He snuck a vertical wire up the neighbor's chimney (standing on his own roof) and ran a radial wire down each side of his own roof. He fed it with open wire line. He managed DXCC in about 6 months, mainly on 40 and 20.

Don't be put off by old amps because they don't have WARC bands. There is no need for an amp on WARC bands. The 30 meter band has a legal power limit of 200 watts anyway (in the US). The 17 and 12 meter bands are like the other high bands, where propagation either exists or doesn't. Very few contests are allowed (if any) on the WARC bands, so you don't need an amp to battle the big guns, and the Big Gun DXers generally don't have much going on 17 and 12. The only real feature drawbacks to old amps are the high voltage keying issue and the absence of 160, where you really do want an amp. I agree with those who advise replacing the electrolytic caps on the SB-200 and other older amps. They do tend to drop in value as they age. Soft start is not required on either the SB-200 or SB-220. The transformers have enough series resistance to keep the tube filament inrush below the manufacturer's specs. All ham amps of that era used power switches that wear out with or without soft start, so the threads you read about using soft-start to protect the switch are meaningless.

As I said in my prior posting, in the amplifier area, you can benefit a lot from a very small amount of homebrewing.

The only amp company today that's building smaller amps is Ameritron. At their price, they are doing things to cut costs, but my view of the amps while at Dayton suggests that they're using components of equal or better quality than the old Heathkits, so they're probably quite functional. Plus, they'd have 160 built in and already be equipped for low voltage keying. The designer of the amps, W8JI, is no slouch. Just gaze at his webpage w8ji.com to see for yourself. My only caution is that if the AL-572 comes with Svetlana tubes, I'd opt to buy the amp tubeless, and purchase some Nationals or other Chinese brand. I'm not convinced Svetlana is past their tube problems.

AM
 
RE: Help, I Need a Cheap HF Amplifier!  
by KA3POY on August 23, 2002 Mail this to a friend!
Jim: thanks for another thoughtfully written article on a timely topic. I hope that you soon post a follow up article on the next grade of amps, the 3-500Z etc.

With regard to the controversy that popped up about amps vs. antennas, I hope that we can all agree that every ham should constantly work to optimize system gain, starting with his antennas. In my case, Home Owner Association rules are inhibiting my ability to raise a 60' tower with stacked monobanders, etc., so I have to live with semi-concealed wires and a Force 12 vertical dipole, the wire antennas get changed every week or two in an effort to get the best result. Clearly, there is a large and growing group of suburban amateurs for whom the old saw about needing better antennas rather than amps isn't very helpful.

The other argument is the old "you don't need an amp you just need better operator skill". On cw, I partially agree with this. As the years go by I do find it easier to "crack" cw pileups using 100w and a dipole that I would never have been able to get through before. If I never used an amp I would still collect a reasonable amount of dx on cw.

However, on HF SSB, with all due respect to the doubters out there, I do see a role for a modest amp in my shack. To work phone contests in the hi-power category, for instance, it would seem logical to use an amp. Also, the cluster-created dx pileups on 20m at night are very tough to get through on 100w and a wire - your mileage may vary, but that's my experience.

When I move into my next home, I'll try to pick a place where I can put up a big-gun tower/beam combo. Then, when I'm wielding all that rx/tx gain, I'll try not to condescend to the rest of the masses who are stuck with their verticals/dipoles/zepps/doublets.

:)

73

N5IIT
was KA3POY
 
RE: Help, I Need a Cheap HF Amplifier!  
by N0TONE on August 23, 2002 Mail this to a friend!
K9KJP, I'm surprised your inverted VEE at 50 feet isn't working any better than you say. One of my primary locations is in the Northern Bay area of California. We have very lossy soil. There's a California Traffic net nightly on 75 meter SSB. The vast majority of the stations who check in are running 100 watts to antennas no higher than yours. The net routinely has checkins from the northern part of the state to the southern part of the state, about 800 miles. I don't know how far the "upper midwest" is from you, so you'll have to do that comparison.

Feeding an inverted vee with coax is not a tragedy, but must be carefully considered. Any imbalance in the VEE will result in coupling to the coax. There's no tragedy in having the coax radiate, BUT - now you've turned your coax into a vertical radiator, probably with no radials. So it's a dreadfully inefficient radiator, and approximatly 90% of the power coupled to the coax will be sent earthward. If the vee angle is fairly narrow, the SWR is probably high. If the VEE is at 50 feet, then the coax run is longer. The SWR measured at the shack is always better than the SWR at the antenna feedpoint. If your un-tuned SWR at the shack is 3:1 or worse, then I'd encourage you to switch to any form of parallel line, even 300 ohm TV twinlead.

To prevent the coax coupling, you need baluns at the top and bottom of the run. Not just at the top. If the VEE is truly balanced (each end equally far from ground, trees, buildings), then one at the top is sufficient. Choke baluns are essentially lossless - it's just a one foot hunk of coax with ferrite or iron powder cores around it.

Several of the hams in Northern California routinely work 75 SSB ragchews on 100 watts using a G5RV at 30-40 feet height. That's 102 feet long - shorter than an 80 meter dipole. Fed with 34 feet of open wire, then coax with or without a balun, and a tuner in the shack. These guys have signals indistinguishable from a full size dipole at the same height.

As I said in another posting, it's always worth changing something, even if the results are not predictable, about a wire antenna. Every change will provide some benefit, and some drawback, and frequently you won't know which is which until you try it.

When I lived in the midwest (northern Ohio), I did well on 80 meters CW with 25 watts, and a loaded dipole at about 20 feet in height. I was a kid with little income, and at first fed this antenna with RG-58. Realizing how bad RG-58 is with poor SWR, I built a little tuning network in a coffee can, and put it right at the antenna feedpoint. That helped a lot. My rig was a homebrew tube unit with pi matching network, so it could work a wide SWR range. Yet, with this combination, I still could not work everybody I could hear, and it was obvious that many times, the other guy didn't hear me at all. One day, my dad decided to replace the ten year old 300 ohm twinlead on the family TV antenna on the rooftop. He gave me the old stuff. It was cracked and split pretty badly. And, based on how much better our TV recpeption was with the new stuff, the RF performance of the old stuff was, in fact, deteriorated - at least on TV frequencies. Yet, when I replaced my RG-58 (35 feet or so) with it, I was able to hear better and be heard better on 80 meters. I QSOd regularly with stations from Canada to Florida, and all the way to the east coast and as far west as Kansas on 80. Winter time was better, and I even snagged California once. Of course, that was CW, and SSB is quite more difficult.

Also, it's worth noting the use of compression. A compressor, when used correctly, prevents flat-topping. On early solid state radios, I like to set the mic and gain adjustments so that the ALC meter doesn't move, except on the very loudest peaks. This often won't happen during an entire transmission. But most hams set it so that the ALC meter is swinging around a lot, and they're content if the ALC meter rarely exceeds the "max" point on the meter - bad news. In that case, though, you can turn on some compression and at least reduce the maximum peaks. I find I can turn on the compressor, and now run with ALC meter bouncing a little more often. If you have adjustable compression, one target is to compress about 10dB at the peaks. I haven't done the careful study, but several others have, and a compressor, when used carefully, can make your signal's "readability" improve by about the same amount as adding 6dB to your power - or just 1dB below using a 600 watt amplifier. My rig has no compressor, so I built an external RF clipper (mic in, then upconvert to 455kHz, clip with Schottky diode, feed through a cheap 455kHz filter, then downconvert using the same LO back to audio). On-air adjustments with a friend who knows my voice in person helped me set it for better readability without any traces of muddiness. He kindly tape recorded the session, so I could at least hear how I sounded.

So, I'll meet your challenge. Try some open wire line. If you save 3dB in loss, then you've bought yourself half of an amplifier.

AM
 
RE: Help, I Need a Cheap HF Amplifier!  
by K9KJP on August 23, 2002 Mail this to a friend!
Open wire line is not an option, I have to run it up the side of the tree so it cant be seen from 3 sides and and it just wouldnt work if it rained. Plus I have a long run into the house. I could use coax to that point but the run inside the house is longer then the run up the tree.. The key here is being hidden from the antenna hating little old ladies that walk by here twice a day.

I have a balun at the top, I have little/no feedline radiation.

Maybe I'm just a little spoiled from my old ladder line fed dipole/kw matchbox/legal limit setup. I never had a problem at all on 75m phone, I guess I got used to having a 'big' signal on 75.. I'm in knoxville, tn right now and making it to wisconson, illinois, indiana, michigan and minnesota isnt like it was in chicago. I could get away with 100 watts in the winter with good band conditions, unless of course someone moved in 2.5Kcs away with a TS-870 or pro on full bandwith 'wide audio' TX and you disappear into high fidelity audio - or an AMer fired up 4kcs away with with a modified splatterbox. I also had no restrictions in chicago where I lived and a bigger lot.

30 over static crashes are not uncommon here, its a noisy mess - as it was in chicago. Maybe I'm just in a bad spot to work the people I used to work every night for a few years.

I know i can work 25 watts CW and make contacts, I have, I still do (I can do it with 5 watts) but my main enjoyment comes from rag chewing with a group of friends every night in a 1000 mile radius. Like my first post said, its just not merely being 'heard,' its being able to keep up with the big signals in a conversation - not going to happen with 100 watts 99% of the time. Not everyone's bag, but thats my favorite ham thing to do :)

I have pretty much worked the same group on 75m for 4 years now almost every evening and have tried every combination of antennas at my old house but here I am very very limited what I can do, I already had two 'fines' for antennas in 3 months. They watch me like a hawk, its really a shame to be looked down on by your neighbors like a common thief in a fairly expensive subdivision - thats my biggest complaint but not relevent to this post..

Tnx for the nfo,
Kevin


 
Help, I Need a Cheap HF Amplifier!  
by W1SYA on August 23, 2002 Mail this to a friend!
I am replyng to the article. I used an SB200 for 20 years on all bands except 160 meters. Both 572B tubes lasted until I sold the Amp. I purchased an Al811H and later changed the (4) 811 to 572B. I got about 20% more power and a better plate power. The SB200 costs about $350.00 . A good AL811H can be purchased for $650
to $700.00.I wanted 160 meters. Red W1SYA
 
RE: Help, I Need a Cheap HF Amplifier!  
by W8CQ on August 23, 2002 Mail this to a friend!
Hi Don,
Harbach Electronics is alive and well. I took over the business from Allan before he passed away. I moved the company to my home near Indianapolis. Everything is at is was (except it takes a little longer to get items as I work a full time job and buld in the evenings).

Regards,
Jeff Weinberg W8CQ
Harbach Electronics
http://www.harbachelectronics.com
 
RE: Help, I Need a Cheap HF Amplifier!  
by N0TONE on August 23, 2002 Mail this to a friend!
Kevin,

Sounds like you should switch to 300 ohm TV line. I have stapled that stuff directly to a tree, and measured the loss to still be 1/5 that of coax. I have also run it (and open wire with 2 inch spacing) inside the house, through walls etc.

Sorry to hear of the CC&Rs, but as you already imply, you chose that house, so you can't complain about the CC&Rs. I have relatives in K-Ville, and I know there are LOTS of neighborhoods, even with relatively new homes, that don't have CC&Rs. Suffice it to say that you obviously had higher priorities than ham radio. That's probably as it should be, since your kids, your church, and whatever else led you to that neighborhood SHOULD be higher priority than ham radio.

If you think the elderly women wouldn't notice 300 ohm TV line, try it. Smaller width than RG-8 and lower loss. And you haven't tried it yet.

AM
 
RE: Help, I Need a Cheap HF Amplifier!  
by N0TONE on August 23, 2002 Mail this to a friend!
I think a lot of the posters on here are missing what it's like to consider RX antennas on a noisy band.

80 meters has such a hgh amount of atmospheric noise that I can hear EVERYBODY on a 10 foot telescoping whip stuck in the back of my old Hallicrafters receiver.

Just because you can hear everybody on the band does not mean you have a good antenna. True on 20 meters, it's such a quiet band that a better antenna always gets you better reception.

But on 80 meters, a better antenna serves exactly the same purpose as an amplifier - only to get your TX better.

Here are some tests:
1) What's the background noise level at night in the winter on your 80 meter antenna? Should be 50mV RMS or more. That's "true" S9, but shows up as about 20dB over S9 on most Japanese radios - with the preamp switched off.
2) Disconnect your rig. Connect a 1.5 volt penlight bulb to the antenna. Turn off all the lights and let your eyes get used to the dark. You should see occasional glimmers from the light bulb.

If you fail either #1 or #2, then there's probably something about the antenna that can be improved.

There's an exception to #2, though - if your antenna is so far from 50 ohms that you must have a tuner, and you have it inline, then you won't get enough power to light the bulb. You only get that much power if the antenna is allowed to provide broadband power. The tuner limits that.

It is true that you may have the best antenna that fits your lot or budget. But do not think you're there just because you can hear everybody on 80 - we ALL can hear everybody on 80!

As I said before, no matter what you have, try changing it. Make your goal to deliver the best possible signal from 100 watts that you can. Not to avoid an amp, but to make sure that when you DO use the amp, you'll be able to cut through that much more QRN.

The better you make that antenna, the longer the band will be open for you, and the further into summer you can work your buddies,with or without the amplifier.

Yes, I use an amp.

Actually, this thread got me thinking of them again, and I pulled out my old Alpha 76. Sweet little amplifier. Got it in trade for a homebrew Yagi, but had to re-tube, and switched it over to 3cx800s, and QSK'd it at the same time. My favorite amp, but it does need 240VAC. Since it's getting close to 160 meter contest season, it was time to dust it off.

Lately I've been thinking that this amp, and a K2 might possibly be the best 160 meter station one could get. If only the K2 were cheaper....

AM
 
RE: Help, I Need a Cheap HF Amplifier!  
by KO4NR on August 26, 2002 Mail this to a friend!
I use a Heathkit HA-10 Warrior with four Svetlana 811A tubes. Works great for about 600 watts out. 17 meters tunes up just fine with the amp in the 15 meter bandswitch position. I added a T/R relay with a 12vdc power supply and a Negative Bias power supply(Acopian NX-25 with a voltage divider). While not ideal I use the autotuner in my Kenwood 850ATS to tune the input to the amp. I get out fine that way. I only drive it with about 60 watts in. I sat a 12dc muffin fan on top the amp to help draw out the hot air. This amp weighs 90 lbs!!

Also use a Swan Mark 1 with two 3-400Z tubes in Zero Bias. Great amp with 1kw key down. The Tank Circuit components are of high quality and capable of handling more voltage. It runs 2900vdc resting and 2500vdc keyed. I really like mine and would not part with it. It weighs 60 lbs!! The only draw back is that the 3-400Z tubes are hard to find and are expensive. They are the predecessor to the 3-500Z and are about 1/2 inch shorter than the 3-500Z tube. This means you can't replace the 3-400Z with 3-500Z tubes unless you cut a hole in the top of the amp or relocate the tube sockets underneath the chassis. Bummer!! If anyone knows where I can get a couple of full output 3-400Z tubes at a reasonable price let me know. Used is FB!!

As far as the "Sweep Tube" amps I have converted several of the Dentron GLA-1000 series amps to use the Svetlana EL-509/6KG6 tubes. My last purchase of these tubes cost me $13.50 each and they were all new. Got them from KWTUBES. He's on the web and very honest guy to deal with. Never have had a problem with any of these tubes. They are Russian military surplus tubes. The Dentron GLA-1000B has a Tuned Input. Be prepared to experiment with different component values to obtain the best match, especially if you go with the Svetlana tubes. The power supply in these amps is whimpy key down but the amp is a compromise. It is very small but has everything under the top cover and can be carried without the help of a forklift!! I got 550 watts out on SSB with about 70 watts of drive. Key down power is miserable because the plate voltage drops so much. Several of the amps I got were given to me and I even found one on a street corner awaiting the garbage man!!

FAR Circuits offers up new circuit boards(RF Board, Power Supply Board and a copy of the Tuned Input Board used in the GLA-1000B) for the Dentron GLA-1000 series amps as well. They offer as is orginal boards or newly designed boards for using Svetlana EL-509 tubes or a new Power Supply board for use with radial type electrolytic capacitors. If anyone needs a good source for the 500vdc electrolytic capacitors let me know. Less than $5.00 each and they are all new. With these boards you can make these little amps new again.

Amps are needed sometime no matter what antenna you have!!
73,
Bill
 
Help, I Need a Cheap HF Amplifier!  
by N3BF on August 27, 2002 Mail this to a friend!
I owned the Clipperton L with 10 meter capability for several years. I purchased it in 1988 for $450. It was a very reliable work-horse on CW, SSB, and RTTY. If using the Clipperton with 572B tubes, protect your finals by not exceeding 600 mA plate current on transmit.
 
Help, I Need a Cheap HF Amplifier!  
by VE6XX on August 27, 2002 Mail this to a friend!
Hi Jim: Thank you for a well presented & informative article. The responses were many,
& ranged from the logical to the silly. I do not run or own an amp for a variety of reasons, but a number pass through my hands each year for repair. It has been my observation that especially on the "low bands" the in-band noise in the U.S. phone bands is far higher than in the "dx" (Canadian ) portion of the band. Atmospherics are atmospherics and are not respecters of geographical location, but I believe that the proliferation of kilowatt sigs exacerbates an already difficult situation. No, I am not suggesting that amps be banned or power levels lowered, I merely make an observation fior what it is worth.
The comments regarding antennas are of course, correct. Since roughly 80% of our population is now urban(exactly the reverse of the pre WWII situation) competent antennas are difficult to erect on city lots.
The 500 or 600 watt amp, as has been stated by others, represents a reasonable solution to the dilemma
without attempting to equal VOA. Jim, I look forward to seeing further objective submissions from you, like this one or your receiver articles. Thank you & thanks to all who posted rational responses.
CHEERS! Brian, VE6XX
 
db's any way you get 'em  
by KA1EZE on August 27, 2002 Mail this to a friend!
The way I see it is hams will get the db increases they want either way! The only advantage to getting the antenna situatio better is hearing, I agree.

I don't think high power gets you a signal better than anyone else, but it may get you a signal more consistant.

In my experience, by listening, there isn't any way I can tell what a ham's power is, other than it remaining at a consistant level over time vs lower power.

BTW my concern isn't with restrictions, but radiation. My antennas are not far away enough to put anything of high power out and meet fcc regs!

rick
 
Help, I Need a Cheap HF Amplifier!  
by WB9GKZ on August 28, 2002 Mail this to a friend!
Cheap Amplifier? What have us hams evolved to? A hoard of appliance operators, yessiree! Back in my time, we stripped out old color TV's and mounted components on pine boards. We wound coils with copper tubing on coffee cans. We toiled for hours to re-weld the filament in that 250TH. Ameritrons and Heathkits....BUNK! A real ham can MAKE his own "cheap" amplifier in a few hours in the basement while the wife and kids are crying for new shoes and milk to drink! I'll give you a cheap amplifier...you
*&%%$$$!
 
RE: Help, I Need a Cheap HF Amplifier!  
by N8FVJ on August 28, 2002 Mail this to a friend!
I can also build RF amplifiers. Repaired a lot of vacuum tube equipment. One issue now, the individual parts cost more than complete amplifiers for sale now. Even Fair Radio Sales can not sell you a plate xfmr. Also, hams are also busier than ever now. Until the old stock dries up, it is a matter of time and economics! Being a cheap Ham, I'll buy the SB-200 & read technical books & articles. Signed, 'Not retired in Michigan'.
 
RE: Help, I Need a Cheap HF Amplifier!  
by NZ5L on August 28, 2002 Mail this to a friend!
Also, don't overlook the possibility of increasing intelligibility by proper audio processing. An old VOMAX split-band processor did as much for my signal on 75 as the SB-200. Couldn't use the amp with the processing so sold the amp. (Personally, I now feel that if I need an amp to "compete" with my fellow ham I'll just try another band, time of day, mode, or just pull the plug and watch the tube.)
 
RE: db's any way you get 'em  
by N0TONE on August 28, 2002 Mail this to a friend!
KA1EZE, I'm not sure I understand your radiation concerns. If you look at the FCC radiation limits calculation, you will notice that the lower frequency is, the closer it allows you to be to the antenna. My 160 meter vertical is base-fed, ten feet from the shack. The FCC equation says I can operate up to 5kW in it before I exceed the radiation limits. Of course, I don't run 5kW.

However, if I choose to feed that antenna on 20 meters, I am now restricted to 100 watts.

We really only encounter radiation limits on 10 meters and above, unless we're attempting to load our operating chairs!

AM
 
Help, I Need a Cheap HF Amplifier!  
by DK3QN on August 31, 2002 Mail this to a friend!
Hi All,

From my experience with amplifiers over the past 33 years, the first 400 watts or so make the difference. This already gives you a one S-unit or 6 db increase in signal strength over your barefoot 100 watt TRX.

If you would want to get another S-unit or 6 db increase, you'd need to output some 1500 to 2000 watts already!

Not only is that a lot more radiated energy with all the side effects which accompany such a power level.
Additionally, it increases the price for a purchase significantly as well as it does increase the cost for spares (tubes, switches etc.) substantially in case you need to repair the unit.

My favorites are single 3-500Z amps or dual 572B's.
Driving it with a modern TRX (i.e. transistor finals) requires an input matching network provided by the amp. Otherwise the high input SWR on some bands will fold back your transceivers output power resulting in low overall output.

If the amp does not provide an input matching network you still can overcome the related problems by using your TRX's internal tuner or adding a small manual or automatic tuner between your TRX and the amp.

Where to Buy:

I would recommed to visit some flea markets and get the deal from there.

On eBay, prices go up towards the end of an auction. On flea markets, it's the other way around, much better suited to get a bargain deal. And you can at least visually check your amp before buying.

73, Klaus, DK3QN
 
Help, I Need a Cheap HF Amplifier!  
by W5LZ on September 1, 2002 Mail this to a friend!
Just a word to the wise about substituting 572B's for 811's. It
can be done, but it isn't as simple as just pulling one tube and
sticking in another.
An 811 tube uses a lower plate voltage than the 572B. This lower
plate voltage results in the 572B running 'soft'. That means that the
tube will not be as efficient, and your signal's bandwidth tends to
get broader than normal. It also means that you will not get the
'normal' full output from the 572B.
One common 'cure' for this low plate voltage, at least with an
Ameritron AL-811 amplifier is to use a lower AC plate voltage tap
on the 'buck/boost' transformer. That does increase the palte
voltage, but it also increases the filament voltage (very bad news!).
Even a slight increase in filament voltage shortenes a tube's life
by quite a bit. So, that isn't exactly the 'best' way to do things.
There is another problem too. The heat generated by the 572B's
is going to be even more than the 811 tubes. That increase in heat
can do some 'odd' things in the Ameritron amplifiers. The plate
coil is constructed with plastic spacers, and that plastic spacer
tends to melt/distort in high heat. When it distorts enough to make
contact with anything else in the amplifier, it's enough to ruin your
whole day!
Substituting a 572B for an 811 is 'doable', but it's a little bit more
envolved than just a simple 'pull -n- replace'.

Paul / 'Doc
 
SB200  
by N1YRK on September 1, 2002 Mail this to a friend!
I remember reading somewhere that the SB200 has its tubes mounted sideways, which causes the filaments to sag over time and break. Is this true? Is it really that much of a problem?
 
Help, I Need a Cheap HF Amplifier!  
by KG6AMW on September 2, 2002 Mail this to a friend!
Ok, I need clarification here. If the power supply in the Ameritron 811 amp is rated at 1700 volts and 550mA, and it runs close to its limit with 811 tubes, then why would putting in 572 tubes generate more heat?
 
RE: Help, I Need a Cheap HF Amplifier!  
by AB5Q on September 2, 2002 Mail this to a friend!
Nice write up, bottom line is to stick with amps that dont use sweep tubes. Im going to deviate from the subject and jump on my soapbox for a minute.....

Homebrewing an amplifier is cheap IF one has a nice stash (junk box) or access to inexpensive components. Building an amp is relatively simple; finding the right parts cheap takes time and is becoming harder. Attitude regarding homebrew is, I got the cash, need the amp yesterday and who cares how it works as long as it does. When it breaks, call it mint and sell it for a premium on eBay, right? Oops another forum, sorry.

On some modes and bands (80m/160m) there is no low cost substitute for QRO. An amplifier is fine as long as it is used only when necessary. Its the attitude and mentality of the user controlling the amplifier I worry about the most these days.
 
RE: SB200  
by N0TONE on September 3, 2002 Mail this to a friend!
N1YRK, the SB-200 and Yaesu FL-2100B both mount the tubes sideways. There were some brands of tubes which could not survive this operation well, but the original spec Cetron 572B tubes were rated for horizontal operation, and all the tubes that I am aware of that you can purchase today are rated for horizontal operation. The SB-200 and FL-2100B probably represent 75% of all the 572B applications out there, so a manufacturer who doesn't rate the tubes for horizontal use is silly. It should be on the tube's data sheet.

AM
 
RE: Help, I Need a Cheap HF Amplifier!  
by WA2JJH on September 3, 2002 Mail this to a friend!
So true. Have used more than 100W maybe a few times. I built a greifkit SB-2000 amp. 1KW. conduction cooled. No fans. The worst part of the construction was tighting the bolts on the berrylium oxide tube heat dissiapator. If Berrylium oxide chips...The dust can be a health hazard.

I noticed no great difference between 100W and 900W PEP.

The inverse square law states that in order to double the distance, you have to square the power.

To double distance from 100W into a non gain antenna, one would have to use 10KW. So with 2KW PEP out, you maybe increasing range by 50%.

So yes, one can do much better with a beam antenna with just 100W. Like you said if you cant hear them well, you will not be able to blow your way though with power.

Also a good RF SPEECH PROCESSOR, not a cheap audio compressor type will help. I notice on my Kenwood TS-850SAT when I set my watt meter to average power a great change takes place. Without the processor my watt meter reads 15 watts average(not PEP) RF processor on, high boost on,and heil mic set on DX mode, My average output power shoots up to 60 watts average. In the PEp mode the chsnge of course is not as dramatic. Also Audio with the high end extended helps.

I am amazed what pile ups I break though using only 100W. I am competing with those using the legal or maybe not so legal power.

 
RE: Help, I Need a Cheap HF Amplifier!  
by WA2JJH on September 4, 2002 Mail this to a friend!
I actally do have to retract a little. After seeing another hams artical. He said put a 1.5 volt pen light bulb accross your antenna line in noisy conditions. Turn off the lights, and in a noisy band condition you will see the lamp glow very slight.

Actually I saw this trick 25 years ago, using a neon bulb. Put it across your antenna line. If the bulb seems to be on all the time...Fire up your amp!
You have your justification for QRO. Otherwise I still go by physics, to double your range, you must square the power. In other words you need 10KW to double the range of 100W. The magic number of 600 watts will not double your range, but will give you the extra S unit to make the contact.

I believe the biggist bang for the buck is 500 watts, with the best RF SPEECH PROC, YOU GOT. The kenwoods always had the edge on RF procs. Also if you can boost your high end TX audio, great. Do not waste time with audio speech procs. The amount of distortion
makes them useless. I have a watt meter that does average as well as PEP power. Without RF proc and high boost mod, I get 20W average. Kick in RF proc. 10db compression, high end boosted, I get 60watts average.
On PEP mode you do see that needle hang around the 100W mark as opposed to the 50W mark.

A good RF proc will make your 500W amp really do it's job. Just hope your power supply and tubes can handle it! I do agree going the legal limit is a waste of money. I agree with Steve Katz that I would not take
in a legal limit amp for free, just because of the weight and shipping. I have had 2 abdominal hernia surguries as it is.

I do not think those with the bux and the abdominal strength should be branded as a CBer type mentality.
Hey..they past the ham exams we did. If they want to run the legal limit all the time, they do have the ticket to do so. They should be nicely enlightened instead. The inverse square law applies to just about everything that deals with power and distance. Just ask any hollywood lighting guy.

BTW the neon bulb across the antenna line trick also makes a cheesy lighting alert detector. You can detect lighting very well. You can just use a long wire instead of your antenna. Hook the long wire up to one end of the neon bulb. Ground the other lead to anything. If you see the bulb almost completly on and you hear thunder less than 30 seconds later, you might want to disconnect your coax from your rig.


I also agree CW rules for noisy conditions. Worked japan a few times with 100W CW.
 
RE: Help, I Need a Cheap HF Amplifier!  
by N0TONE on September 4, 2002 Mail this to a friend!
A neon lamp across the antenna terminals tells you something completely different than a penlight bulb. A neon lamp is high resistance until it fires. The antenna can build up static discharge until there's enough to fire the bulb. I can make a neon lamp fire even when bands are dead, if the current weather is low humidity with wind.

The penlight bulb has a low DC resistance, so it drains the static charge. It can only be illuminated by a "notable" amount of power being recieved.

Also note, the inverse square law applies to a point source radiating into free space. When you view the globe, and consider that the volume available for radio propagation is bounded by the few hundred miles of the ionsophere, you can see that we're actually considering a curvilinearly mapped boundary layer, and not free space. This is equivalent to a line source radiating into free space, and the relationship is inverse, not inverse squared. That's why it's entirely possible to be audible only 100 miles away on 1 watt, yet at 10 watts, audible on another continent.

Yes, CW is a wonder. West coast to Japan on 40 meter CW is a nightly occurrence with 1/2 watt and a dipole at 30 feet. I own an amp, but on CW, have only needed it on 160, where my antenna is a major compromise. However, even though I'm a CW hound, I recognize the great wonder of ham radio is in the variety, so I also operate SSB, and am glad there are so many who do.

AM
 
Help, I Need a Cheap HF Amplifier!  
by W9GB on September 7, 2002 Mail this to a friend!
A nice review of "what's available on the market. I would like to make some follow-up comments:
[Removing the "urban legend" and replies I read that were "misinformed"]

Harbach Electronics
The original company has been split into 2 separate companies (both owned and managed by amateurs)

Jeff Weinberg, W8CQ, purchased the Amplifier business. Still providing quality replacement parts for the SB-200 and SB-220 owners.
http://www.harbachelectronics.com

The Antenna business was purchased by N0BD.
The Antenna Parts division is now known as DX Engineering at: http://www.dxengineering.com
-------------------
Parasitic suppression is required for some of the amplifiers mentioned. Harbach has the kit for the SB-220.

I would "highly" recommend that any amplifier read the articles by Richard L. Measures, AG6K. The "arced" band switches photographs submitted by other amateurs are very revealing of the problem.
http://www.vcnet.com/measures/

SB-220 specific comments:
http://www.vcnet.com/measures/sb-220.html
-------------------
Anyone thinking of using 572B tunes in the Yaesu FL-2100B amplifier MUST read the required circuit changes for proper operation.
http://www.rfparts.com/technical.html
-------------------
In general:

1.) Sweep tube amplifiers which were cheap beginner amplifiers in the 1960's and 1970's are going the way of the "Dodo bird" (extinct). Many have been badly abused with CB and "free" band usage. [Look at the junk sold on eBay as "amateur equipment" - since eBay will not allow these units to be sold in the CB auction section. Quality units found should not be abused, if using US sweep tubes or converted to the Svetlana EL509 (eastern Europe) sweep tube.
I agree with Jim's suggestion - sell the tubes to the other poor guy who has one and strip the unit as a parts unit for auction / hamfest sale OR other projects.

2.) While glass RF amplifier tubes will be around for a couple of more decades, they are a declining market -- as metal/ceramic tubes are now the norm. The price difference will decrease over the next few years.

3.) Large sources of parts of the Heathkit SB-200 & SB-220 series exist. Complete replacement front panels are available on eBay .. Restorations and repairs are easily with the capabilities of many amateurs [remember this was a kit]

4.) I have seen quality Collins 30L-1 units within the price range mentioned here. A number of these units are surplus from government and military. Many units will require a "recap" and replacement HV diode board.

5.) Dentron is a mixed bag of quality and "eras", with a variety of units - some better than others.

6.) I chuckled when I saw the Hunter Bandit mentioned. It works, but I have yet to see one that was not in bad shape or belonged to a heavy smoker [low resale value without heavy cleaning]. An excellent quality unit may qualify as a museum piece - with appropriate eBay price.

73 de w9gb
 
Help, I Need a Cheap HF Amplifier!  
Anonymous post on September 8, 2002 Mail this to a friend!
At this point, I think buying any amplifier, new or used, is becoming a crap shoot. The day of the demise of the power tube is alot closer than most think and solid state amps aren't going to be a good alternative. Most of the traditional buyers of power tubes are quickly disappearing. Broadcast stations, government, industrial users are abondoning tube equipment. The commercial buyers that are still buying keep the few tube manufacturers in business. It sure isn't the ham market that keeps Eimac, National, ect. going. It never did. Ham radio always, with few exceptions, got good tubes developed mostly for goverment contracts.

As time passes the desireable tubes are going to get even more expensive than now. 572's, 3-500's, 811's, ect. are going to keep going up. Forget the 8877, 3cx800, ect., they will become (if not already) out of site.

Other factors like power transformers, chokes, other parts that are hard to replace will transform what appeared to be a good used purchase into a true piece of junk if they fail.

So what is there to buy? If I were in the market for a "cheap" amp I would be considering those amps that were very plentiful (junk units for parts); amps that used the most easily replaced tubes like the 811, 572, 3-500, 4-400, 4-250, ect.; this list would include a lot of amps that may not be under $300, but in the long run it may be cheaper to buy a L4b than some amp using sweep tubes or a Heath sb230 that uses a $600 tube.

 
RE: Help, I Need a Cheap HF Amplifier!  
by N0TONE on September 8, 2002 Mail this to a friend!
I repair a lot of amps, and have done a more thorough investigation into them than most people have equipment to do. Someone used the phrase "urgan legend", and there are definitely urban legends in amp lore. I won't try to dispell any, but rather, will present some information I have gathered, either through professional contact, or via measurement.

First, off, tubes. What's going to be available? What won't? The Eimac company began life as a supplier of tubes to the ham market, and only later began their foray into commercial tubes. Two of their tubes, the 3CX800A7 and the 3CX1200A7 were aimed directly at the ham market, with only secondary thought given to commercial uses. However, it is true that a major manufacturer can not survive on the ham business alone. Fortunately for Eimac, their metal/ceramic tubes are built with a certain commonality of components and techniques, so they can afford to keep tubes in production for a while. Here's a "short list" of tubes that are or once were built by Eimac, and the sort of usage/availability to expect:

4CX250B series - These tubes and their variants are found in hundreds of thousands of broadcast transmitters as drivers. They were manufactured by several different companies. The new sales of these tubes continue at a brisk pace, and they'll be around a long time. However, be advised that unless used carefully, they have a very fragile control grid, and they are famous splatter generators. If you have an amp that uses them, for the sake of your on-air brethren, keep the power below 200 watts per tube. In commercial use, they were ALWAYS used class C (FM rigs, mainly, plut plate-modulated AM) and really weren't intended for linear service.

3CX400A7/8874 - Also used as drivers in many broadcast rigs, they could have been plentiful. The price, however, kept them from replacing the 4CX250B in pairs, so they're not so plentiful. Production still continues, but the price is dear. Electrically the same as the 8875, which bolts to a heatsink and is impossible to find.

3CX800A7 - This tube was intended for hams. However, its ease of drive, freedom from parasitics and amazing robustness meant that it found its way into a lot of commercial and industrial applications. It's often used as the pre-final in broadcast FM transmitters, and there must be tens of thousands produced annually for medical and industrial uses. Eimac recently proposed that all users of this tube switch to the 3CPX800A7. That's the same tube, but with a slightly larger anode-to-grid insulator spacing, to allow the use of higher voltages. It will drop into any application designed for the 3CX800A7, and exhibit fewer arc incidents.

3CX1200 series - there are a few tubes in this series. I have rarely seen them in commercial applications. Eimac claims they'll be around for a long time, and the best news is that this tube is so rugged that you rarely have to replace one. There may be a bigger market than is obvious though. One tube in this series is pin-compatible with the old 3-1000Z used in broadcast rigs. As that glass tube becomes unavailable, many of those old rigs will be refitted for the 3CX1200A7. So there's a definite re-tube market.

3CX1500A7/8877 - Possibly more popular than the 3CX800A7. This tube is used all over the place in medical, broadcast, industrial. They'll be around a very long time.

Summary - you won't go wrong with the 3CX800A7/3CPX800A7, 3CX1200A7 or 8877, in terms of future availability. Pay particular notice to the fact that the 3CX800A7 and the 8877 have both been produced by companies other than Eimac, attesting to their popularity.

Russian tubes - This could be a mixed bag. ALL of the tubes with labels like GS-35, or GU-74 come from the Russian military. A tube with a number like 4CX800 is of recent, known manufacture. When I have purchased 4CX800 tubes, they've arrived with mil surplus numbers. So far, I have not seen a recent manufacture 4CX800. On the other hand, I HAVE seen recent manufacture 4CX1600B tubes - but they were hard as hen's teeth to get. The Russian supply is not as yet stable.

If you're a homebrewer, by all means go for a Russian tube. On the upside, since they're mainly tetrodes, you'll be building an amp with a spare supply in case you have to switch later to a triode. Homebrewers have it easier, since they can modify the amp later for "other" tubes.

Sweep tubes - basically, avoid them. The original reason for using sweep tubes was because they were cheaper. They were intended for us in TV sets. Nobody makes TV sets with sweep tubes any more, and people who have sets that old are throwing them away when they blow a tube. They were never used in broadcast transmitters and virtually not used in any commercial RF gear. Because of the scarcity which they already exhibit, the prices are no longer cheap. You can purchase a single 572B tube, which has 8X the plate dissipation of most sweep tubes, for $35. Most sweep tubes will set you back $20. Today, they are not cheap per watt. Also, any prior design which used sweep tubes did so to avoid higher prices, so that gives you a clue about the quality of the components used in the rest of the amp. I've seen a lot of smoked power transformers in sweep tube amps, and not many in amps with transmitter tubes.

Glass tubes - This is not the mixed bag that some have claimed. The "golden era" of broadcast transmitters used 3-1000Z, 4-1000Z, 3-500Z, 4-400A, 4-400C, 4X2500 and on and on and on. In the US, many of those transmitters still serve small markets, and when a tube dies, they want to replace it. Sometimes they'll opt to replace the glass tube with a ceramic/metal equal, and sometimes not. BUT, there is a third market out there and it is HUGE. Third-world countries operate broadcast facilities, and to them, price is a major object. Many of them are operating old "surplus" US-built transmitters or even "homebrew" transmitters. They mainly use glass tubes in grounded-grid. Have you ever wondered WHY there's more than one company making the 572B? Or why there's more than one company making the 3-500Z? Or why ANYBODY is still making 866s? It's because there's a big market. Don't also forget the "industrial" market. In the world of plasma etching, semiconductor sputtering, LCD display sputtering, there is a need for cheap RF power. The Henry company serves a lot of customers in this industrial market, and they want watts per dollar. The 3-500Z is found all over the place, and so is the 4-1000Z. Don't discount glass tubes yet. In fact, when I look at my price comparisons of tubes, the "cost benefit" for going with glass tubes in terms of dollars per watt has never been better than today. The glass tube prices have stabilized, partly because there are so many suppliers, while the metal/ceramic tube prices have continued to climb.

The 572B requires a note: The Svetlana version of this tube began life intended for audio. That's why its cutoff bias voltage, when repackaged as a transmitter tube, isn't what it should be. This causes grief in the Yaesu FL-2100B. As long as you avoid Svetlana tubes, the 572B is a fine tube. The current Svetlanas might be OK, but the data sheet characteristic curves do not suggest that it's been redesigned.

When buying a used amp, which glass tubes are OK? The 3-500Z is a good choice, although many amps designed around it are "iffy". The 572B is a good choice. The 811 found itself in a few amps that were marginal, but the tube's fine and available. The 4-400A/C can be replaced with a 3-500Z, so no reason to steer away from it. Lots of hams like the 4-1000Z, and supplies seem acceptable. The 4PR1000 is a drop-in replacement that's used in a lot of industrial gear, so it should be available, although it's getting pricey.

With respect to "all those modifications" that are out there for amps.

1) High voltage arc protection isn't a bad idea. Most amps with 572B tubes used a design which incorporated "accidental" arc protection in the grid circuits. Most 3-500Z amplifiers used a grid circuit that grounded the grid better, but did away with the "accidental" arc protection, so one should seriously consider adding such protection, in the form of series resistance in the HT supply and diode protection across the meters.

2) Most oscillating amplifiers don't have a parasitic suppressor problem. The absolute exception to this generalization is the Kenwood TL-922, a beast that's hard to tame. Some of the Heath SB-220s, if built with poor attention to lead dress under the tube socket, can have problems, too, but the better cure is to redress the grid and cathode lead arrangement. Unfortunately, the SB-220 design makes it hard, and even dangerous, to work around parts of the cathode circuit, so a more aggressive suppressor may often be the cure.

The SB-200s that I've seen oscillating all had damaged grid resistors. Those are the various one watt 33 ohm jobs under the tube socket. If they rise in value above about 60 ohms, the amplifier will oscillate. If you're going to use carbon composition resistors to replace old resistors, definitely measure the "new" units first. Carbon composition resistors drift upwards in value as they age, whether they have current flowing or not. A recent box of resistors I measured, which was still in the original manufacturer's sealed box from 10 years ago, had not one resistor in tolerance. This box of 47 ohm 2 watt resistors all measured 90 ohms or more. There is a new ceramic composition resistor available that solves this problem, and since it's a bulk resistive material, it should also have the benefits of carbon comp - low intrinsic inductance, and high instantaneous overload capability.

The SB-220s I've had on the bench never really suffered an oscillation condition due to the normally-accused suspects. In many of them, what I found is that the bandswitch contacts had gotten dirty with age. This resulted in the contact not quite being made. There was some small arcing right at the switch, between the two pieces of metal that were SUPPOSED to be in contact with each other. That arcing caused voltage and current transients in the tank circuit, which led to things like arcing tune capacitors, and "big bangs" caused by dielectric breakdown from things as non-obvious as tank coil-to-chassis. It is amazing how many direct arcs I have visually witnessed that left no arc marks at all.

3) Bandswitch damage: The SB-220 is one of many twin 3-500Z amps where some components are "on edge". The circulating current in the tank is too high for the bandswitch. The burned bandswitches on AG6K's website clearly shows the pattern. The current through the closed contacts is too high. As a result metal heats, and deforms, ultimately losing contact. The RF circuit is completed by a small arc, which is so quiet you don't hear it over the amplifier's fan. The metal continues to deteriorate until there's not much contact left. About the time the contact you're interested in (say you're mainly a 20 meter operator, and it's the 20 meter contact) is gone, it now arcs over to an adjacent contact. In most of the photos on AG6K's website, the major damage is between switch rotor and the intended contact, not an adjacent contact. This indicates that the "made" contact set deteriorated first.

Also note that it requires a lot of long term arcing to create the level of damage shown. I have intentionally arced a bandswitch by using high Q networks following a 10kW amplifier. If I arced the switch for 5 minutes, followed by a cooldown of 25 minutes, then arced it again, I could do this for weeks, and not have the damage shown on AG6K's website. However, if I intentionally melted a contact with too much current, I could create the amount of damage shown in 15 minutes. You don't get that much carbon damage until you've melted some metal, which requires current.

Summary of damaged bandswitches for any amp, not just SB-220: Clean them periodically with CAIG's DeOxit. I prefer a bottle, not a spray, and the use of Q-tips for application. As long as you're not running a twin 3-500Z amplifier on keydown RTTY, you should not be able to damage a clean bandswitch.

I've drifted off on tangents, obviously. Many of us are amplifier addicts. I just love tinkering with them. But, for the purposes of this thread, here's the summary:

1) A list of ceramic/metal tubes of Eimac origin was presented that is likely to be in good supply for the foreseeable future.

2) A caution was presented for any tube sourced exclusively from Russia

3) Sweep tubes were strongly recommended against

4) Glass transmittering tubes were suggested as being low risk, particularly the 811, 572B and 3-500Z.

5) Encouragement of arc protection was given, for early amplifiers with twin 3-500Z tubes

6) The automatic installation of parasitic suppressor "upgrades" was discouraged, except for the TL-922. Instead, it was recommended to consider checking/replacing all resistors in the grid and cathode sections, and to carefully and thoroughly clean the bandswitch.


And one final note: I've had exactly three Collins 30L-1 amplifiers on my bench. After cleaning switches and tube sockets, they all performed flawlessly. Nobody built tube gear like Collins.

AM
 
Help, I Need a Cheap HF Amplifier!  
by W6RLF on September 9, 2002 Mail this to a friend!
Jim,

Thank you for an excellent post. A lot of interesting comments, though some make me shake my head, especially those who continue to harp on the antenna issue, as if the answer to every problem is a better antenna.

I guess I'm sensitive to this, as I've always had to make due with simple antennas (dipoles, wires, and a vertical for 20/15/10); and I've always lived in one valley or another. The lot configuration is such that I can't get anything too high, and I have other compromises.

I use 100W whenever I can, and never more than 100W on CW; also do a lot of CW QRP. On a quiet band, when conditions are hot, you can work anywhere with just about any power and any antenna; we all know this. (In last year's All-Asia contest, I worked a couple of Japanese stations with 2 watts out.)

But on a noisier band, and/or conditions are not optimal and/or against "competition", you may need something more especially if you CAN'T do anything more with your antennas. I check into a West Coast net on 75 SSB; I run my Ameritron ALS-600 at about 350W out (cut back because of the nature of my wire antenna situation.) With that, I'm still not heard by everyone on the net up and down the coast; if I'm barefoot (and I've tried), very few hear me.

I also use the amp on dx chasing/contests; with my antenna realities, and typical (not super hot) conditions, on SSB the amp is often the difference between being in the noise and not being heard, even calling in the clear, and getting through. And before someone asks, my vertical is in perfect condition, well situated, with perfectly tuned radials.

Many have summed it up well: Do the most you can with your antennas; and if at best you have some site/location limitations, going from 100 to 400-600 watts out is a godsend at times.

Paul W6RLF
 
Help, I Need a Cheap HF Amplifier!  
Anonymous post on September 9, 2002 Mail this to a friend!
I love the internet....Full of bad information. Power grid users may find this information of interest.
The last 2 tubes Eimac made for Ham radio was the 3-400z/3-500z and the 3cx1200d7. The pre 3-400z was Eimacs answer for a tube for the 30l1 amp. Collins went with the 811 instead mostly from time limitations that Eimac could not work with. Eimac ended up making the prototype/idea into the 3-400z.

The 3cx1200d7 was developed for Henry Radio. The 3cx1200a7 was too tall to fit into a table top amp Henry wanted to build so Eimac made an oem special version of the 1200a7 which later became the generally available 3cx1200d7. The 3cx1200a7 was developed for a commercial application. But note this. The 1200d7 is not electrically the same as a 1200a7. It is different internally and the d7 does not have the 15 - 20 mc instability problem that the a7 does have. If you have a choice, buy a d7. Filament voltage is also different.

The 3cx800a7 was developed for a US Marine Corp linear amp. It found a very small commercial market when made available for the general public.

The 8877, 8873, 8874, 8875 were originally developed as an experiment. Eimac wanted to make a triode version of the 4cx1500b which used the focus cathode and worked very well but screen grid tubes were dangerous in the hands of users who like to blow the screen grid. The oxide stripped cathode tubes found a market AFTER they were developed.

FOR THOSE WHO BUY NOS OXIDE CATHODE TUBES ON THE INTERNET......PAY ATTENTION!!!!

Oxide cathode tubes (thoriated tungsten to a smaller extent) will start to deteriorate in as little as a year on the shelf. Legit distributors of Eimac tubes buy tubes a year or more in advance and time the deliveries over the year to meet buying habits of their customers. Eimac gets calls all the time from people who bought NOS on ebay and got a dead or half dead tube. Sorry no warranty from Eimac for these tubes.

Also, don't replace a 4-400 tube with a 3-500z in an amp made for 4-400's. The bias and screen supply won't like that.

This information came from an applications engineer who still works for Eimac CPI.

 
Help, I Need a Cheap HF Amplifier!  
Anonymous post on September 9, 2002 Mail this to a friend!
As an aside to my previous posting, one could say that no Eimac tube in the last 55 years was developed from the beginning to be an amateur tube since the 3cx1200d7 and 3-400z were derived from tubes that were not initially intended primarily for the ham market. It depends on how you consider a 30l1 amp. Also, this information is offered "AS IS".
 
Help, I Need a Cheap HF Amplifier!  
by WA2JJH on September 26, 2002 Mail this to a friend!
After all I have been reading, I am going to build a solid state 500W out amp. Motorola has been selling 250W power bricks for land mobile/navitime for a while.

Two bricks in a high power combiner. To avoid a hefty suppy. I am going to use A TODD High frequency switching supply. 13 volts @60 Amps. weighs 5 pounds!
I bought 20 of them at a ham fest. Even at retail cost
they compare well with the conventional 12volt boat anchors. This one, I powered a ts-850, ts-50, and a 150 watt VHF amp,all at the same time. No problem. The supply is rated for 750watts continous. I will look for thier 1kw supply to power the two 250W bricks.

I know the more pikyune will attact my method.
I hate tubes. The ceramic used in ceramic tubes is BeO
berrylium Oxide, a known carcinogine. If you chip BeO,
hold your breath.

Also after reading much about questionable sources of glass tubes, I know going solid state is the answer for me.

In broadcasting most Transmitters under 25KW are solid state. Guess what many solid state modules combined. One module goes south, you loose a miniscule
amount of power. You can HOT SWAP the module.

500W solid state, with a high frequency switching supply is the way I AM going to go.

I do not care what feedback I will get from know it all, OCD-AR's DSM-IV look it up
 
RE: Help, I Need a Cheap HF Amplifier!  
by RADIOWEENIE on November 25, 2002 Mail this to a friend!
So you need an HF Amp, do you? While i certainly do sympathize with the author of this article as far early evening 80m is concerned, i do not believe that such power levels are at all necessary or even desirable. My "big rig" is 50W with an inverted Vee. Sometimes i run QRP with that antenna. And I have never (repeat NEVER) run more than 100W. Most of the countries in this world limit output power to 400W and it is an extreme rarity to find a country that permits even 500W. That certainly does appear to be more than ample. The most frustrating aspect of Ham Radio is not that my station has too little power. The most frustrating aspect is that i cannot get thru on 20m because some loudmouth in TX is running 3000W and doesn't want to acknowledge that there is anyone else on the band but him. If the power output here in the US were limited to, say 400W, then we would not need to be thinking about KW amps because there would be much less QRM to cut thru. QRO is a vicious circle: The more the other station has, the more we want, and the more I think I need. Obviously then, it has to stop at some point: so why not stop at 400W? Good luck, fellow hammies!!
--R.W.
 
RE: Help, I Need a Cheap HF Amplifier!  
by W7ITC on March 30, 2003 Mail this to a friend!
I really like my SB200, pairs are easily to find. Go here http://www.harbachelectronics.com/ I like what these Heathkit amp's SB200, or SB220 are called in some parts of the country "Green Pigs" you key them and they keep on squealing.
 
Help, I Need a Cheap HF Amplifier!  
by WA2JJH on May 2, 2003 Mail this to a friend!
I want to go solid state. I just want about 400-500 watts PEP. I have access to 60 amp 13 volt light weight
switching power supplies cheap.

So I have the power supply. I know motorola sells
solid state 250W 2-30 mhz modules. I could use a power combiner and two modules.

Anyone know of any places that sell these modules?

TNX MIKE
 
RE: Help, I Need a Cheap HF Amplifier!  
Anonymous post on May 16, 2003 Mail this to a friend!
Communications concepts sells kits of parts including boards. I built 2 1.2kw amps using their parts and they work well.
 
RE: Help, I Need a Cheap HF Amplifier!  
by KB2SDR on June 13, 2003 Mail this to a friend!
WA2JJH,


There is an amplifier that is made by an Italian company, RMITALY. They make a 600w amplifier for HF mobile, kl-500. I have heard people talking about it on 80mtrs and they say they work pretty good. I would imagine that you would have to put better filtering on it. For $215, sounds like a good deal. Look at the following link, these mps are always on sale on ebay.

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=4671&item=3029124376

73
Jason
KB2SDR
 
Help, I Need a Cheap HF Amplifier!  
by WA2JJH on June 20, 2003 Mail this to a friend!
I just purchased a heathkit HL-2200 on ebay. There seems to be no info on it. I paid $550, did Iget ripped off?
 
Help, I Need a Cheap HF Amplifier!  
by K7KQ on September 10, 2005 Mail this to a friend!
TRy a RMItaly Linear Amplifier - HF with preamp. Covers all bands up to 80 meters. and dose not cost you more than $280.00.
 
RE: Help, I Need a Cheap HF Amplifier!  
by K5MO on September 24, 2005 Mail this to a friend!
The RM amps with receiver preamps, appear to be nothing more than cheap dirty CB broadband amps, that flood Ebay.

I do have an one of their solid state ham models (HLA150), which is very nice. Auto bandswitching, multi-pole filtered output on each band...they're nice amps.

On THIS model (HLA150), the only think likely not meeting FCC type acceptance, is its coverage of 10m and the low drive requirements. Apart from this meaningless requirement (which has done exactly ZERO in getting junk CB amps off the marketplace) the ham band RM solid state amps, are quite nice, and a great accessory for a QRP rig. My K2 easily drives mine to 120W out on 20m CW.
 
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