[Amps] Need Smarter Than I Am Help.

[Bob D.]

Is IMD higher at higher plate voltage? From the 73 Eimac data sheet, for
AB2, it's worse at 2.5kV than at 1.5 or 3.5.

Then there's context.
CW?
For an amp originally designed for 1kW/2kW CW/SSB input with a transformer
good for 800 W, when replacing it with one good for 1400 W CCS, it makes
sense to raise the plate voltage at the same time. I picked up a fast
vacuum relay for my 'new' L7. It seems sensible to upgrade the power supply
and re-work the tank while it's on the bench for QSK. Plate dissipation
should be about 250 W per tube at 1500 W output. With Morse code duty cycle
it will be about half that. So no need to upgrade tube cooling.

Set it up to switch to half voltage on occasion for some plate glow...

Anyway, that's what I'm considering for the L7.

If running heavy speech processing and long winded, an upgrade makes even
more sense.

73, -bob ah7i



> Message: 1
> Date: Mon, 11 Oct 2021 04:49:48 -0500
> From: Rob Atkinson <ranchorobbo at gmail.com>
> To: "amps at contesting.com" <amps at contesting.com>
> Subject: Re: [Amps] Need Smarter Than I Am Help.
> Message-ID:
>         <
> CALWD7Z6btHYiqxbS4gJ4w_Dsmg2iFGf4-jQ-3v7HBnYznTsnNg at mail.gmail.com>
> Content-Type: text/plain; charset="UTF-8"
>
> Why do some of you guys want to jack up the plate v. on your 3-500s?
> The power difference won't be noticed and you'll create a cascade of
> problems.  You still have the same plate dissipation and plate current
> limits.  The pi network won't work, the DC blocking caps may become
> marginal, the power supply filter cap bank may get stressed and the
> IMD spec. gets worse.  If you want to jack up the B+ get a 3-1000Z.
>
> 73
>
> Rob
> K5UJ
>
>
> ------------------------------
>
>