Bill Turner wrote:

You can do a pretty good evaluation of a tuner's loss by putting your hand
on the cabinet after running a few minutes. Just imagine a 25, 50 or
whatever watt resistor in there dissipating the same heat.

One needs to calibrate one's hand, of course. :-)

Bill, W6WRT


I disagree.

I'd venture to guess that the average output power of a 100 watt PEP
sideband rig is no more than about 10 watts unless heavy compression is
being used. And I think you'll find that a 10 watt resistor inside a
typical tuner cabinet -- representing loss of all the transmitted power
-- will make a barely noticeable difference in the cabinet temperature.

Add to that the fact that the thermal time constant of the tuner is
probably longer than the typical transmitting session, so the power
needs to be averaged over the receiving periods, too.

If you're running a kW, you're up to 100 watts or so during transmit
only. But can you tell the difference with your "calibrated" hand
between 1 dB loss in the tuner (25 watts), 3 dB loss in the tuner (50
watts), or 100% of the power lost in the tuner (100 watts)?

I'd love to see the results of a double-blind study where a measured
tuner loss is compared with an estimate made using Bill's method. But I
think the chances of that are about the same as finding a double-blind
study of the audio quality enhancement of $1000 speaker cables.

Roy Lewallen, W7EL