[Amps] GS23B Plate load resistance for HF

[Bill Turner]

ORIGINAL MESSAGE:          (may be snipped)

On Mon, 28 Oct 2013 22:29:53 +0100, N8ZFM wrote:

>
>Using a spreadsheet I got from G3SEK. I am using the following values, 3000V
>on Anode, max of 1A DC anode current and planning on getting 1500W output,
>using a K factor of 1.5. So the implied efficiency is 50% and a plate load
>of 2000 Ohms, all well and good but 50% seems low and I would think I would
>be closer to 60%. 

REPLY:

For what it's worth: I have built two amps using the GS35b and had the same
low efficiency you indicate above. Several European hams have reported the
same. It appears that 50% is all the tube is capable of. If you can tolerate
that, otherwise it works well and is very inexpensive. Going to a much more
expensive tube gains you only about 10%.

As to what causes the low efficiency, I can only guess. I suspect the grid
structure does not have complete control over the electron flow and allows
some current to "leak" past it. That's just a guess, I am willing to stand
corrected if someone has a better answer. 

73, Bill W6WRT