[AMPS] 3-500Z Grid Current Rating

[M.J.Willis]

I have a single 3-500Z amplifier. When I run it at 2.4kV EHT at the rated 400mA
of anode current, I get 450W out with 130mA grid current and 60W drive. This
is on 50MHZ. The problem with this is the low efficiency and subsequent 570W
anode dissipation.

I can make the amplifier more efficient my letting the grid current increase - I have
a low EHT after all, but at 175mA Grid current and 350mA anode current I get the same
power out - 50% efficient and within ratings at 450W anode dissipation.

How can I calculate the grid dissipation ? Is 175mA Ig really too much?

It is easy to get the grid current down by increasing the EHT. Much more output can
be had as well - I know as I have put 3kV on the valve. As our power limit is 400W at 
the antenna, 2.4kV (on load) is adequate if the grid dissipation is OK and is easier on 
the PSU. Drive is not a problem as I have 100W available.

Mike


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