[Elecraft] Perplexing output power behavior for K3(s)

[Jim Brown]

On 3/17/2025 2:36 PM, Bob McGraw wrote:
> Now the reason for stressing known good 50 ohm load, I have 3 different 
> brands, and power dummy loads.    Although all say "50 ohms" they are 
> not!  One is 57 ohms (air type load),  one is 48 ohms cold and 53 ohms 
> hot (Cantenna) , and the third is 50.5 ohms (Bird 100 watt load).

Great advice. There are "dummy loads" and precision dummy loads. I own 
about seven, two of which are VERY high precision for calibrating my 
vector network analyzer well into the UHF range, and rated for about 1 
W. The others are professional loads, intended for use with 
transmitters. One is rated 500W continuous, and I saw its twin on the 
bench where my KPA1500 was been tested under load. The others are rated 
for lower power. All of those transmitter loads measure within 1% cold, 
and all of the transmitting loads were bought for pennies on the dollar 
at ham flea markets.

A dummy load is a precision resistor, constructed in such a manner that 
parallel capacitance and series inductance are quite small, so a rough 
measurement of its precision, especially at low HF, can be achieved with 
a high quality, high precision, and well calibrated Ohmmeter.

73, Jim K9YC