Don, Thank you. I tested separately. When using the P3TXMON, the calibrated tester was not in the transmission path. I actually did what you suggested in your second paragraph.
As another test, I borrowed another ham’s Elecraft W2 SWR meter. I replaced the PSTXMON with the W2. The readings using the W2 software utility were close to the readings from my tester, about 1.08:1. Significantly, different than the reading form the P3TXMON of 2.0:1. 73, Bob Bob Nobis - N7RJN [email protected] > On Sep 8, 2015, at 15:23, Don Wilhelm <[email protected]> wrote: > > Bob, > > How are you testing? > If you are testing with the P3TXMON and your 'calibrated VSWR tester' in > series with your feedline, then those numbers may be incorrect. > The 'calibrated VSWR tester' is reading the SWR seen looking into your > antenna, but the P3TXMON is looking at the SWR looking into the input of your > VSWR tester - and that may be two different things. > > If you want to do a valid test, obtain the SWR reading on your VSWR tester, > and then take the feedline off that tester and connect it to the P3TXMON > directional coupler and compare the SWR reading obtained from that > combination. > > In other words, while your VSWR tester may be calibrated at its output, there > is no guarantee that its coupler does not introduce an SWR at its input. > Switching the same coax from the output of your tester to the output of the > P3TXMON is the only valid test. > > 73, > Don W3FPR > > On 9/8/2015 1:49 PM, Robert Nobis wrote: >> 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? >> >> > > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected]
