Ferris, is the sensor for the TX MON mounted directly on the ANT connector on your K3S? (no coax jumper to the sensor).
The reason for the question is this. The tuner in the K3S adjusts the impedance the K3S's finals see to 50 ohms at the input to the KAT3 inside the K3S, but the impedance the KAT3 sees at the ANT connector to the coax might be quite different. That's what the KAT3 does. It transforms whatever impedance it sees at the ANT connector to 50 ohms, non reactive or as close as it can get and that's the SWR you see reported. It tells you the K3S finals are delivering power most efficiently to your antenna system. But it does nothing about the SWR on your coax feedline to the antenna. Unless your feed line is exactly 50 ohms and it is seeing exactly 50 ohms at the antenna, there will be standing waves on the feed line. The idea is to keep them low enough to prevent excessive feed line losses, but the SWR is virtually never zero. The impedance at any point along your feed line will vary as you move from the rig to the antenna. That's dependent upon the SWR on the feed line and the frequency. Any feed line between the sensor in the KAT3 and the sensor for the P3 TX MON will cause them to see different impedances and so they will report different SWRs. The best way to check the two is to mount your P3 TX MON sensor right at the K3S ANT connector with a double male adapter so there's an absolute minimum of feed line between the KAT3's SWR bridge in the one in the IX MON sensor. Ideally terminate the TX MON sensor in a good 50 ohm dummy load instead of connecting it to the antenna. Then both SWRs should agree within a reasonable range. 73, Ron AC7AC -----Original Message----- From: Elecraft [mailto:[email protected]] On Behalf Of Ferris Jennings Sent: Friday, December 18, 2015 4:36 PM To: [email protected] Subject: [Elecraft] KS3/P3 SWR Display Readings Hell-o Everyone - Finished building my K3S and P3 (with TX Mon), and I'm starting to play with the configuration/menus. I have the KAT3 ATU installed, and it works great. But I do have a question regarding the SWR displays. I'm running a simple diploe, and the KAT3 tunes it down to 1.0-1 in a second flat. However, the SWR meter on the PS display always reads way higher, something like 2.9 - 1. I've swapped antennas and lead (another dipole), and I get the same results. Question is: why the discrepancy in SWR from the K3S display to the P3 display? Am I missing a configuration setting? Thanks -Ferris NB6T- ______________________________________________________________ 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]
