At 09:20 3/31/98 +0100, you wrote:
>It would be a terrible waste. Using a UHF tube like a 7213 on HF would
>be like using a high-spirited racehorse to pull a cart.
Well, Ian, I must agree with that statment. However, out here in the middle
of the desert, there is a real lack of VHF/UHF types. Email me direct and
I'll tell you all about it. The tube was originally obtained for use in a
432 amp when I was still doing EME. That project fell by the wayside, and
the tube has been in a drawer for years. I have given up trying to find a
trade for it and decided it would be fun to try it on 1.8 or 3.5.
>Worse than that,
>in triode-connected grounded grid (TCGG) the poor beast would be dead in
>six months.
>
>I don't have the characteristic curves for a 7213, but most of the RF
>drive in TCGG goes into the control grid, and modern ceramic-metal
>tetrodes do not have the control-grid dissipation to handle that - and
>in TCGG you can't even measure the screen and control grid currents
>independently. If experience with 4CXC250s is anything to go by, TCGG is
>a quick, sure way to ruin the tube.
>
I wonder how true that is in this case? My old RCA tube manual only lists
class C operation but does give 0.2 amps as max grid current. Don't sound
real delicate to me.
>The 7213 is rare and desirable for use at UHF, so why not trade it for
>an 8877?
I just checked again, not many folks lined up in the driveway wanting to
trade!
73,
Larry - W7IUV
w7iuv@axtek.com
www.axtek.com/w7iuv/
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