[Amps] cavity temperature

[David and Wendy Dodds]

Hi all.

I'm almost finished putting together a 23cm cavity amp - just a single 7289 round cavity, similar to N6CA's design.

My concern is cooling. I'm using forced-air cooling, which seems pretty effective in that the exhaust air never gets dramatically hot, even when running cw for a protracted period of time. What does get hot is the anode tuning control, presumably due to convection along the shaft (which is only 1.5 inches long) The Eimac spec sheet for the 7289 shows a safe maximum operating temp of 250 degrees celsius, so I guess it's ok for the cavity to be pretty hot!

Should I be worried that this is an indication that the cooling isn't sufficiently effective or am I worrying too much?

I haven't come up with a safe (and cheap!) way of measuring the temperature of the anode fins. I could probably get to them down the exhaust chimney, but as they are at 1100v I don't fancy poking a thermometer down it (even if I had one that went up to 250 deg!)

Any ideas, thoughts, suggestions?

Tnx es 73

de David GM4WLL


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