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+1 on the blocking cap. I have a 2xGI7B project on the go for 144MHz with a very similar set up, and the looming possibility of thermal drift is a great concern. I thought about employing one of those

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G'day Tim. Check (physically and electrically) your plate blocking/coupling capacitor very carefully. John, VK6JX, had the exact same problem with his GS35B model 2m amp, using what looks to be the

Thanks for that information Lou and thanks to Doug for the leg work. Carl, along with Rich, Tom, Ian White, Tony King, yourself, Jim and lots of others are the ones that have fed me with knowledge,

This amp was made in 2001 indicated by 11-01 all over the inside of the amp. No Heat on the Plate Choke. Looks bright red all over. I see no cracked caps at all neither. I just had time to take it

Hi Everyone, I built this little 2m amp a couple of years ago, it works perfectly in every way..... except for the thermal drift. Tuned up with key down, 300W out with 12W drive, within a few seconds

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With 3 phases anode voltage will be completely different as will be the rectifier stack. 73 Peter, DJ7WW -----Original-Nachricht----- Betreff: Re: [ham-amplifiers] Building my first amplifier. Where

Ummm... before you settle on that monster, you might want to fire her up and measure the idling current, no-load. Then again, with some temporary load resistors across the secondary. The results just

First thing I'd do is copy the spreadsheet and revise the dropped Ep to no more than 2500V, perhaps 2550 at most, then design for that reduced value. Unless you're in a commercial establishment, with

GI0UTE. Thanks des

Hi Desmond, What is your Ham Radio Call Sign? Thanks, Walter KR4HV Sent: 26 December, 2023 12:48 PM To: [email protected] Subject: Re: [ham-amplifiers] Building my first amplifier. Where to

Hal, I might message g(m)0sek if I struggle,thanks for the advice. I have a 3 phase transformer with various taps. It's rated 20kva. I have tried single phasing it, and it runs ok. Less capacity

Peter, Thanks for the advice. Ok, I understand the issue can be stray capacitance and inductance? I see this project happening in stages, eg build with what I have and some extra pieces to prove the

Des, GM3SEK relocated to Scotland some years ago. I believe he will still correspond with amateurs who face design complications. I still would like to know what your power supply might consist of.

I would use capacitors as small as possible, not those monsters. You want all connections within the tank circuitry as short as possible. I have good experience winding coils by using the program

Hal, Yes, one of concerns is "committing" to a tube that dries up by way of availability.? That's why the GS35 and Gu43b are on my radar,as they seem so plentiful.? If i do get an amplifier up and

Was discussed some years ago on the amps reflector: <http://lists.contesting.com/_amps/2007-10/msg00036.html> Its a low ? generator tube with poor iMD and high drive requirements. 73 Peter, DJ7WW

Dear Des, Some years ago I invested money into whar was then a seemingly up-and-coming amplifier that used a GU-78b. The first thing I did when setting the amplifier up was to seek out a spare tube.

Jim, I found a reference on the net to someone who has build an amplifier around the GU5b some time agai and he stated gain was low and required 200w drive to maximise output. Here is a link to the