I have an older K3 that is producing excess power at the higher requested
power settings. It has had the gold pin modification done to it and has
worked well for years. I have calibrated the wattmeter and Tx Gain. Things
track very well until about 90 watts. When requesting power above 90 watts,
the K3 power sensor stays at 90 watts, and the actual output goes up to over
120 watts. I've attached a plot of the internal and external power
indications vs. requested power.
Here is a link to the plot (tested at 14.175 MHz):
K3_SN00728_Power_Curve
<
https://1drv.ms/b/s!AokL5oqT_SkggZdv5V2W_l6aR4yfvA?e=tIWT4W>
Other info (in anticipation of comments and questions):
1. External measurements were taken with an LP-100A wattmeter and
corroborated with a calibrated scope and spectrum analyzer.
2. Transmitter was connected through the LP-100A sensor to a Bird 30dB
attenuator, and additional 30 dB attenuator, and then terminated in a 50 ohm
input on my spectrum analyzer.
3. The PA temperature varied from about 35C to 45C during the test. I
started at the highest and lowest power settings and worked inward towards
50W which is why that temperature curve looks the way it does.
4. The problem is repeatable.
I wouldn't squawk about this except that it appears that something is broken
in the K3 power sensor. It tracks beautifully through the 5W and 50W
calibration points, but then has issues at the higher power levels.
Also, on some bands the power is so high that I get HI CURR warnings and
power foldback.
Any ideas?
73, be safe, have fun!
Rick
N1RM
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