[Amps] GS-35B

[David Smith]

Hi John,

The GS-35b is designed for G-G use (the grid ring doubling as a chassis
mounting point), and for a reason.  If you try to use a GS-35b (or any
triode) in a grid-driven configuration on 2m, you'll almost certainly end up
with a nice 2kW oscillator suitable only for cooking the Christmas turkey
:-)  The reason is that the feedback (output to input) capacitance within
the tube is much higher in that configuration.  In grid driven, this
capacitance is formed by inter-electrode capacitance between grid and anode,
which is of the order of 5pF.  In G-G, the grid acts as a capacitance
shield, so the output-input capacitance (anode to cathode) drops
substantially to around 0.1pF or less.

So, for VHF-UHF use (and, I would say, HF), G-G is really the only option.
However, it is a very good tube.  I use one on 70cm and it performs
extremely well - around 13dB of gain in G-G.

Perhaps you need to build a 4CX250 driver for it (with extremely well
regulated screen supply) ;-)

Regards,
Dave
VK3HZ