Randy, If your LP100A is on the antenna side of your KAT500 then you are putting your LP100A in the region of higher SWR if your antenna is not close to resonance. I think you would want to put your LP100A in the inboard side of the KAT500 so that you are properly showing the “tuned” SWR on the LPA100A and your readings will be more accurate I believe.
If you want to know the antenna side of the SWR, what the KAT500 refers to as the Bypass SWR since it is the SWR you see if you bypass the KAT500, then you can use the KAT500 utility program to display that. I am not seeing the problems you describe. For example, when I run without the TX Mon Sensor in place, there are absolutely no SWR problems at all (look again at the configuration below that I have). I should also note that today I did not see any problems with the SWR spurts I originally reported even with the TX Monitor sensor inline. 73, phil, K7PEH > On Aug 12, 2015, at 7:48 PM, Randy Farmer <w...@tx.rr.com> wrote: > > I find this thread quite interesting. I too have been dealing with VSWR > "spurts". My TX lineup is similar to Phil's, but I don't have the TX Monitor. > After a recent station rewiring job I found I was having a great deal of > trouble with indicated VSWR jumping to high levels with the amplifier on. The > problem was especially bad on 80 meters -- anything above about 300W would > randomly give a high VSWR fault on the KAT500. Since the KPA500 was feeding > the suddenly changed load it too would usually fault out. The sensor for my > LP-100A is on the antenna side of the KAT500, and its VSWR indication was > rock solid during these events. My station is in an extremely difficult RFI > environment, with seven antennas crammed onto a 0.2 acre city lot. I > immediately suspected that common mode RF was getting into the reverse power > sensor circuit in the KAT500. > > I installed a Balun Designs choke on the antenna side of the LP-100A sensor > and the KAT500 stopped giving the high VSWR indications right away. That's > the good news. The bad news is that now the KPA500 is doing it, but at > considerably higher power levels. I can run around 400W out before the KPA500 > begins to randomly show VSWR faults. The KAT500 is completely stable at full > power. For now, I'm living with this situation. > > So I would suggest the troubles you're seeing may be the result of common > mode RF problems on the transmitter feedline. It could be that the addition > of the extra electrical length of the TX Monitor sensor and its associated > cabling changed things just enough to put a common mode voltage node near the > KAT500 output port. You might try adding an additional piece of coax > somewhere in the lineup and see if that changes the situation. RF is funny > stuff. > > 73... > Randy, W8FN > > On 8/12/2015 10:10 AM, Phil Hystad wrote: >> Mike, >> >> Thanks for the comment. I only have one K3 with one P3. My configuration >> is: >> >> K3/P3 —> KPA500 —> TX Mon Sensor —> LP100A Sensor —> KAT500 —> >> 80-meter Dipole >> >> I first noticed the spike with the RED LEDs on both the KAT500 and the >> KPA500. I was not looking >> at the SWR display on the P3 although the second time I did notice that it >> too spiked (max reading). >> >> Like I said, I was operating CW and when I sent just the first dit of a QNI >> into a CW net the spike occurred. >> I stopped, and then keyed again and everything was normal. The second time >> that I did this, I thought that >> maybe the spike was momentary and continued keying but the second or third >> key down action (actually, a paddle) >> resulted in fault with the KPA500. >> >> Last night, I did not have any problems at all because I disconnected the TX >> Mon sensor. I will continue >> experimenting though as I don’t have too many data points yet to draw >> conclusions. >> >> 73, phil, K7PEH >> >> >> >> >>> On Aug 12, 2015, at 7:28 AM, Mike VE3YF <m...@ve3yf.com> wrote: >>> >>> Phil: >>> >>> I have the same setup but only 1 x P3. A K3 and P3 on my left setup and a >>> K3 on the right setup using a MK2R+ and I noticed what you mention only >>> once. I was on 80m with >>> the Right K3 and I saw a brief Power and SWR spike on the Left P3 and K3. I >>> might have had a bit of SWR on the standalone Right K3. I have not noticed >>> it happen since, it might >>> be a band/swr specific issue ie, as I was operating around 3800 and the >>> antenna is designed for the CW and RTTY portion of the band. The Left side >>> radio was on 160m Sloper >>> >>> >>> >>> >>> 73 De Mike >>> VE3YF >>> >>> http://www.ve3yf.com > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:Elecraft@mailman.qth.net > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to phys...@mac.com ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
