Maybe it's a combination of the dainty 4W grid and the small physical size.
It's not a very big tube. Those numbers came straight from the data
sheet so I'll bet they contain some institutional
"fudging" of the numbers to keep people from running it flat out.
I've seen designs around the net that say they are getting 1 to 1.2 KW
SSB out of a single 3cx800A7.
If that's true then Eimac must be De-rating the tube a little bit like
small aircraft engine manufacturers do their engines, so they've
actually got a chance of making the TBO (time between overhaul) rating
of the engine.
Expensive tubes, expensive engines.
On 8/24/2015 5:21 AM, Bill Turner wrote
REPLY:
That's interesting. At 2250 VDC and .6 amps, the DC input is only 1350
watts. At 60% efficiency, the RF output would be 810 watts and the
plate dissipation would be 540 watts.
The tube's rated plate dissipation is 800 watts, yet in class AB with
max Vp and Ip, you come nowhere near that rating. Most tubes will put
out RF well in excess of their dissipation rating. For example, a
3-500Z with only 500 watts plate dissipation will put out 750 watts
and still be within ratings.
The question is, why would a tube have such a high dissipation rating
if it is not capable of reaching that in normal class AB operation?
Perhaps it is intended for use in class A?
Seems strange to me. Your thoughts?
73, Bill W6WRT
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R. Kevin Stover
AC0H
ARRL
FISTS #11993
SKCC #215
NAQCC #3441
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