Especially if you're only looking for 1500watts of CW, why not 4CX250B's? 4
of them, 2kV at an amp or so, and you're there. You should be able to pick
them up reasonably cheaply with sockets. Over here, I'd reckon to get
sockets and 4 tubes for under $150. You could probably get away with 3 of
them if you pushed the HV to 2500v. According to my book, they are rated at
1500v in plate modulated service, which gives a peak plate voltage (crest of
modulation, crest of RF waveform of around 4500 to 5000 volts, so pushing
them to 2400 or 2500volts in CW should be OK. And if you really are CW only,
you don't need anything too fancy by way of screen grid supply.
Do you really need instant on?
The big advantage of 3-500Zs to my mind is that the blower requirements are
such that it's likely to be reasonably quiet.
73
Peter G3RZP
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