[1000mp] al-1200 plate voltage

[Ron Weaver]

Well I seem to have generated a lot of interest on the al-1200 plate =
voltage. oops. The al-1200 is designed to operate at about 3600 volts. =
In my version there are separate plate and filament transformers, with =
adjustable taps to compensate for differing line voltages. The real =
advantage is getting the filament voltage correct. Eimac states that =
running a tube over the stated filament voltage will dramatically reduce =
the tube's life (ww.eimac.com see care and feeding)

You can use a lower tap to increase the plate voltage, at the risk of =
the capacitors, rf-choke and bandswitch.
I would not recommend this unless your plate voltage is less than 3600 =
no-load.

A cw carrier of 100 watts should produce about 800 mils plate current at =
3300 volts (2640 watts input) and at 66% efficiency that's about 1742.2 =
out, into a pure 50 ohm resistive load (less if reactive), and plus or =
minus your watt meter's accuracy, typically 10% unless you have a high =
dollar meter. plenty plenty.

My comment was really directed at the tube, which will really bark at =
5kv, Eimac's max rating, and output about 4kw with 250 watts of drive. =
Eimac's typical operating condition is 3600 (coincidence ?)

I have driven my 1200 with 135 watts of drive from my mk iv, into a =
dummy load of course, briefly, just to peg the watt meter :), but I =
typically run the mk iv in class A mode, let the amplifier coast, and =
make 1200 or so watts. very cool.

apologies for the noise and confusion,
KB8ELK


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