Hard to capture wonky SWR situation
Good afternoon all, during these days of high temperatures along with high humidity comes severe weather. Storms that bring high winds, lots of rain, sometimes hail and most often lightening. When there is a threat of these storms I remove all connections from my antenna to radio and related radio equipment. I have a 3x5 card that reads "antenna disconnected" that is put in front of my power button on the Icom 7610. It's there to remind me what I did as in the past I have actually turned the rig on and was greeted with an out of this world SWR when I attempted to transmit. On the back of the 3x5 card is a list of what has to be reconnected.  

Well back to the topic at hand, I had my cables disconnected and the 3x5 card in place as we did have some severe weather roll through town the night before. I connected the cables, turned on the radio and started my PC. My plan was to get some FT8 contacts in the log before supper prep had to be done. As my rig was transmitting my LDG 200AT pro II turner started clicking which meant it was going through a tune session. This was odd as the tuner memory already selected the sweet spot and it was proven by the SWR meter on the Icom 7610. BUT......as I continued to transmit the SWR was going "wonky" and the LDG tuner was engaging to correct the issue. 

There sure was an issue and I'm not feeling good about it. My troubleshooting began and here is what I did:  

  1. I went to antenna 2 on the Icom 7610 which was connected to my dummy load. I transmitted into it at full power for about the time of an FT8 transmission. The result was no SWR issue so the 7610 seemed to be ok. 
  2. I then connected the LDG tuner between the dummy load and my transmitter. I know there is no miss-match but if the LDG tuner was acting up it may do it in this ideal matched situation. The result was the tuner did nothing when I transmitted. 
  3. I do have an LDG antenna switch (LDG DTS-4) in the maze as well. Once again I transmitted into the dummy load through the LDG tuner and then the LDG DTS-4 to the dummy load. Low and behold the tuner was trying to find a match again! 
In the past, I did have an LDG antenna switch with a bad relay and it seems this may be the case again. I examined the coax connections and there was one very slight loose connection. I also exercised the relays by switching from one antenna position to another and back again. Once this was done the SWR issue was gone. My BIG mistake was I did not check the conditions after I tightened the PL-259's before I exercised the relays. If I did it would have been clear where the issue exactly was. You know what they say " hindsight is always 20/20" I have not had the problem since but one thing for sure I have narrowed it down to the LDG DTS-4 switch or coax connection to it. 

Mike Weir, VE9KK, is a regular contributor to AmateurRadio.com and writes from New Brunswick, Canada. Contact him at [email protected].

2 Responses to “WHAT THE HECK!!”

  • Harry K7ZOV:

    Hi Mike,

    The loose, as in not snug, PL-259 connector has bitten me more then once. Although the connector felt shug, it was in fact kind of floating and making my SWR jumpy and unstable. Once I found the issue and really got the connector to seat tight no other issues… I have also seen this reported on groups I have been in and once I clued the ham to check the problem went away

    Over the past 50+ years I also had one other issue that caused me fits… Floating braid in the PL-259 housing. The first time it was not my connector but a local ham. He used a under rated soldering iron. the holes had solder, but when I got the tip hot enough to melt the solder and pulled the coax came right out and sure enough no solder on any of the braid. It happened to me also a couple of times. I thought I did a good soldering job… Turns out I didn’t.

    Good luck with your setup. I have been buried in yard work and it looks like I will finally have time to get back to the radios. Digital with the IC-7300, Satellite with the IC-9700, Chasing DX with the TS-990S beast and so fun and games with the Xiegu G90… I am liking it more and more and glad I sold the KX2.

    73 to you and yours


  • Mike VE9KK:

    Hello Harry and good Saturday evening from the East coast, so far so good with the issue not happening again. I have had this in the past but it has been bad coax that had to be changed out. I find my PL259’s have what I call “teeth” on them and I try to get them lined up with the groves on the SO-239 and most of the time when that is done all is well. This time around it seemed even with the matting of the teeth I still did not get a good tight fit. Well I am happy that it was just the connection and not a relay in the coax switch. I did have a nice mechanical Alpha Delta switch and for some reason I sold it…….it’s famous with me as soon as I sell something I end up needing it, wishing for it back or changing my setup and having to purchase it again.
    I understand the yard work thing as I have been doing the same thing out this way and it’s something that has to be done!
    Harry have a great weekend and have fun with the rigs.

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