Thursday, August 13, 2020


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. 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. 


MadDogMcQ said...

Thankfully, lightening storms are quite rare here in the UK - certainly in the Northern regions, but this week has been an exception and we had an extremely long lightning display which went on for hours right outside the house. No thunder, no noise, just a light show turning night into day. Needless to say, I disconnected the antennas quickly. I must make myself one of those 3x5 cards :-)

VE9KK said...

Good morning Tom, since we have moved to Atlantic Canada last year from Ontario there is not as many severe weather storms down here as there was in Ontario, but we still get them. Very nice to hear from you and I hope you are enjoying the new Icom 9700?