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

To: Amps group <>
Subject: Re: [Amps] GS-35b 10M+6M dual-band
From: Bill Turner <>
Date: Mon, 2 Nov 2015 13:30:41 -0800
List-post: <">>
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On Sat, 31 Oct 2015 19:46:39 +1300, Steve wrote:

>GS35b dual-band 10/6M amp?  Any comments?  Google can't find me a good 
>example of one of these, which is surprising..


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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