I have started building a 7-MHz AM trasmitter with four suppressor-modulated
803s in push-pull-parallel. I expect to get nearly 400W of carrier power.

My only concern is plate voltage. As a matter of fact I plan to use a power
supply that delivers about 2800V under no-load conditions, which is
considerably higher than the maximum allowed plate voltage (2000 V) and I
have no simple means to reduce it.

My intention would be to increase the negative grid bias, so as to reduce
plate current and stay within the allowed plate dissipation.

Does any one have experience of operating an 803 (or an 813 which is very
similar) at a much higher plate potential?

Thanks & 73.

Tony I0JX
Rome, Italy

Il 12/05/2013 18.21, Antonio I0JX ha scritto:
I have started building a 7-MHz AM trasmitter with four
suppressor-modulated 803s in push-pull-parallel. I expect to get nearly
400W of carrier power.

My only concern is plate voltage. As a matter of fact I plan to use a
power supply that delivers about 2800V under no-load conditions, which
is considerably higher than the maximum allowed plate voltage (2000 V)
and I have no simple means to reduce it.

My intention would be to increase the negative grid bias, so as to
reduce plate current and stay within the allowed plate dissipation.

Does any one have experience of operating an 803 (or an 813 which is
very similar) at a much higher plate potential?

Thanks & 73.

Tony I0JX
Rome, Italy


Tony, go ahead, some time ago ( more than i like to remember... hi ! )
i've built a linear amplifier with 3x813, 2500 volt plate, all ok...

Watch the screen grid current, it is a very good indication for
pentodes.
Do not surpass G2 specified current.

If you wish, mail me directly to : piero.soldi(at)libero.it

73, Piero i5spo.