Re: Building my first amplifier. Where to start?
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You don¡¯t say where you are located or provide a call sign so those of us replying don¡¯t know where you are for parts recommendations.
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The Eimac book ¡°Care and feeding of power grid tubes¡± book has a lot of good information.?
This book should be in all Amplifier Builder¡¯s and Modifier¡¯s libraries.
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There is a copy on-line from CPI (owners of Eimac) in six sections.
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Start by looking at Section-3 ¡°Electrical Design Considerations.?
For instance, In section 3 it has sections on Lead Length, Filament Bypassing, Keying, and more.?
Section 3 also talks about Class A, AB, B, and C amplifier characteristics.
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If you find it useful.?
I¡¯d suggest buying a book on-line.?
eBay USA has several for sale. ?
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73,
Dave, w6de
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From: [email protected] <[email protected]>
On Behalf Of desmond auld via groups.io
Sent: 23 December, 2023 10:56
To: [email protected]
Subject: [ham-amplifiers] Building my first amplifier. Where to start?
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Hi guys, I have been subscribed to this list and reading messages for some time, but I believe this is my first message, so hello all. I am a ham based in the UK and have been interested in amplifiers for some time. I have a somewhat basic
understanding of their operation if I'm honest, and currently own a linear amps UK 811 hunter. It uses 4 off 811 tubes, and runs very well. I understand 811's are somewhat delicate, and so I tread lightly with them.
I have always had a notion of building my own hf multiband amplifier covering 80 to 10 ideally.? I have been gathering parts that might someday be useful such as hv transformers, power supply hv capacitors, door knob caps of various values and some big vacuum
caps etc. I don't have everything, but I guess I'm on the way. This approach makes things seem less expensive :) .
When it comes to tubes, I have also managed to collect some "interesting" items. I have a 3cw 30,000 and some gu5b's. The 3cw30,000 is clearly way too big (is there such a thing :) ) but the gu5b's might be about right.?
With the power supplies I have I can supply options. 2.8kv DC, 4.7kv DC, 5.5kv DC. All from a 20kva rated transformer, and voltages quoted are bridge rectified at zero load, not voltage doubled, so I have plenty of supply capacity.? I could tweak things to
get intermediate voltages if useful. I am yet to collect filament supplies, and the thought of a 6.3v or similar high amp supply puts me off so I guess that rules out the 3cw30,000 or similar.
I have been told to start with a triode amplifier as a tetrode is a much more complex beast, which with it's screen supplies etc I can understand.? I have good metal working tools and equipment (Bridgeport mill and welding kit etc) and some electrical test
kit including HV probes and a nano van and an old scope.?
Anyhow, I'm keen to learn as much as I can before I start off on this adventure, can you recommend any good books that are practical in their approach to hf amplifiers? I don't mind maths, I'm an engineer , but practical examples helps set context in my mind.
I have seen this diagram (attached) to an amplifier based on 2 off gu5b tubes. Obviously input circuits aren't described, but I guess it's a start?
Goal is something that will easily do the new 1kw UK limit. 2kw might be a nice max power rating. Am I mad??
Seasonal greetings all, des.?
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