[Amps] tetrodes operating VHF, common grid

[Ian White]

K5PRO wrote:
>
>4CX5000A isn't a great VHF tube, Eimac 4CX3500A is better due to lower
>cathode lead inductance and shorter height. I did a comparison of the
>4CX3500A in grounded grid (with bias) and grounded cathode, at 100 MHz.
>Built both circuits and tested them. It got published in one of the old
>NAB handbooks, as well as an app note from Broadcast Electronics in the
>early 1980s. I may still have a copy if anyone asks.
>

Eimac tubes are far less common in Europe than in the USA, so we tend to
use whatever is available.

But as it happens, three 4CX5000As and a socket are available in Europe
right now, from the estate of a SK friend who was still planning "The
Next Big Amp" until his very last days...

Two of the tubes are as-new rebuilds, apparently unused (I think they
had been spares for GPK) and there is also a new and unused socket by
EEV. I have tested the tubes 'cold' for HVDC and heater continuity, but
I am not able to test them at RF. 

In the same box, I also found two sockets for the Russian GU84B
tetrodes.


Anyone interested, please contact me direct.


73 from Ian GM3SEK