[Boatanchors] Ranger and a 4X1
Mark Shaum
k9tr at dtnspeed.net
Tue Mar 11 07:11:36 EST 2008
Jeff asks:
>Also, how silly would it be to drive a homebrew 4X1 amp with the TX? Any
>thoughts on the best amplifier plate voltage / power out? I'm sure purists
>will be be up in arms on the architecture of not modulating the final, but
>realistically ... this should provide a respectable signal? I doubt I'd
>want to run more than about 400 watts out.
I have a couple 4-1000A's on the shelf with sockets and chimneys awaiting
time for the big bottle project. A grounded grid class B 4x1 might be a
pretty good match for the Ranger, The tube may deliver the 375 watt maximum
AM carrier out with plenty of headroom for 100% modulation peaks up to 1500
watts with the 40+ watts or so carrier level that the Ranger will provide.
But to get reasonable efficiency with the 4X1 in grounded grid you are going
to have to put a LOT of B+ on it. 4kv miniumum, probably more if you are
aiming for the maximum legal output. Drive requirements go way up with
lower plate voltage. Some folks run 5kv or more, that kind of voltage
floating around the shack makes me nervous.
An option might be to wire up the 4X1 in a passive grid driven arrangement
and run it class AB2. I may go that route, with a 1:4 balun at the input
feeding a 200 ohm non-inductive resistor to get the grid drive swing up from
a low power exciter. That way I can likely get by with a more reasonable
3kv or so on the plate.
Mark K9TR
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