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

[Vic Rosenthal 4X6GP/K2VCO]

It's a regular PI network with a small coil between the blocking 
capacitor and the tuning capacitor. So it becomes an L-C-L-C network.

73,
Vic, 4X6GP/K2VCO
Rehovot, Israel
http://www.qsl.net/k2vco/

On 3 Nov 2015 19:57, Steve Wright wrote:
> 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