[Amps] GS23B Plate load resistance for HF

[Bill Turner]

ORIGINAL MESSAGE:          (may be snipped)

On Wed, 30 Oct 2013 21:18:51 -0500, Jeff wrote:

>Bill,
>
>Did you use a tuned input on those two amps?  The reason I asked is that I 
>saw quite an interaction between the efficiency of my gi7b and the tuned 
>input trimming that I was never really able to figure out.
>
>Also, what tank Q did you build the design around?
>
>I'm planning to build a GS35b amp for the higher bands this winter.
>
>73/jeff/ac0c
>www.ac0c.com
>alpha-charlie-zero-charlie

REPLY:

Yes, I always use a tuned input on my amps. Design Q for the output tank was
12 per the G4AXX spreadsheet. 

You might be interested to know that in both amps, I replaced the GS35b with
an 8877, changed the cathode zener and filament transformer and immediately
got into the 60%+ efficiency range. The HV and input and output circuits
were the same. The only conclusion I can come to is the tube itself just
isn't as efficient as others. 

As I said, if you can accept the 10% or so reduction in efficiency,
everything else about the tube is good. Especially the price. 

When you build your amp, you can use a Coleman lantern replacement glass for
the chimney. It fits perfectly and can be fastened to the chassis with a few
dabs of silicon RTV, which is easily removed with a knife if you ever have
to. And of course, it needs no socket, just some careful metal work and some
simple home made clamps. 
Have fun!

73, Bill W6WRT