[BC] Curious

[khcs@juno.com]

Mark observed:

>I recall about 140F on a 25k output 816 Continental, measured about 15"
above the cabinet in a round duct (meat thermometer). Don't qoute me on
the 140, it wasn't the actual number we worried about, but making it as low as possible. 

Part of my lessons on how to tune the radio properly included "tune for
minimum" on the temperature. We didn't measure elsewhere. When you got
desired output and minimum temperature, you were at max efficiency,
basically. 

------------

Quite right.  When I used to work with transmitters that needed to be tuned (<g>) I would use two thermometers -- one in the ouput stack, the other at the air intake.  The difference is what I put on the maintenance log, as just the output temp will vary with the ambient temperature.

I would also use a clamp-on ammeter along with a DVM to calculate the amount of AC power being consumed, and divide that into the RF output power to get the overall efficiency rating.  

If either or both of these is higher than what is normal, you know you have a problem.

Glen Kippel
KHCS
Palm Desert, CA