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[Amps] 4CX1500 QSK

To: Amps Reflector <amps@contesting.com>
Subject: [Amps] 4CX1500 QSK
From: Mark Hill <g4fph@mjha.co.uk>
Date: Tue, 02 Nov 2004 12:09:43 +0000
List-post: <mailto:amps@contesting.com>
Rich,
Karl-Arne,

Many thanks for the suggestions. Having looked at the circuits for the amplifier section, I think leaving the screen Voltage present at all times and switching the grid bias would be easiest. Prompted by your circuit idea Rich, I have dug out a suitable power FET and OPTO that should handle switching duties.

Rich, it seems as though this particular TX /amplifier has been optimised for very low IMD at the 1 kW level - probably because there were lots of them in close proximity to one another. The manual quotes IPs as better than -36 dB on either of two tones (CCIR 326-2). The operating parameters seem to be taken more or less straight from the Eimac data sheet for the valve. I noted you point about the valve being capable of producing more Watts. I may try just a few more Volts on the screen out of curiosity, but the low IMD probably betters my triode units and will be good for local rag chews and digital modes.

Karl-Arne, the Collins sounds like an interesting unit. I hope I don't come across one at a bargain price - it would be terrible to have to choose between a lovely wife and a 'tube with handles'!

Regards.

Mark.


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