[Elecraft] P3TXMON VSWR Measurement Accuracy

[Robert Nobis]

I am having a VSWR measurement accuracy issue with my P3TXMON.  I have a calibrated VSWR tester that indicates my antenna and feedline VSWR is 1.05:1. When I connect the P3TXMON and transmit, the PS display shows my VSWR is 2.0:1 into my feedline and antenna. 

I also tried testing into a dummy load. The VSWR tester shows a VSWR into the dummy load of 1.01:1, whereas the P3TXMON shows a VSWR of 1.29:1.

Power level readings on the P3TXMON are within 5% of measured power levels using a power meter, so the P3TXMON is reasonably accurate measuring the transmitted power.

In reviewing the P3 manual, I do not see any methodology for calibrating the VSWR measurement accuracy for the P3TXMON.

Any suggestions on how to calibrate the P3TXMON for better measurement accuracy?

Thanks and 73,

Bob Nobis - N7RJN
n7rjn at nobis.net