[Amps] GS-35b 10M+6M dual-band

[Steve Wright]

Bill,

Thanks for your tips!  I did seem to me that 10M would just be a few 
more turns on the tank, and it seems now that 12/15 is just a few more 
turns!  I doubt I'd try for 40M as well - it's just not that sort of amp.

If I understand correctly, the L match is just a normal pi network, but 
missing the input capacitor.  I am not sure how that is tuned in 
operation, or if I'm on the right track at all there.

It seems the task will be to build a 6M amp, and see how many bands I 
can add without wrecking 6M operation.


Steve


On 04/11/15 06:00, Bill W6WRT wrote:
>> GS35b dual-band 10/6M amp?  Any comments?  Google can't find me a good
>> example of one of these, which is surprising..
> REPLY:
>
> That's a pretty simple amplifier. You don't really need a specific
> schematic, just follow good design principles. The ARRL handbook is
> your friend.
>
> Just three comments:
>
> 1. Use the "L" matching design to compensate for the output
> capacitance of the tube, which is too high for a "normal" pi network
> out tank circuit, especially on six meters. Details are in any recent
> ARRL handbook in the amplifiers section.
>
> 2. For best efficiency, use a plate voltage of about 4 kV. Running it
> at about 3 kV will cost you about 10% in plate efficiency. 4 kV is
> more than the specs allow for but it works fine anyway.
>
> 3. A replacement Coleman lantern glass makes a great chimney because
> of its modest cost and high heat resistance. Hold it in place with a
> couple of dabs of silicon RTV and put a few temporary spacers between
> the glass and the anode fins to position it while the RTV dries. If
> you even need to remove it the RTV is easily cut with a knife. Measure
> the diameter carefully to be sure you get the right one, since Coleman
> makes several different models. The right one will have a gap of about
> 1/8 inch between the glass and the fins, which is perfect.
>
> Sounds like a great project. Have fun.
>
> 73, Bill W6WRT
>
>
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