Wednesday, June 10, 2015

WHAT an SWR of 99:9!!

The other evening I had an opportunity to get on the air it has just been to long and I was very excited about spinning the dial around the HF band! I ran the coax out to my MFJ 1788 on the balcony and fired up the K3. I jumped on 20m were not to much was happening but on 30m there was some Dutch DX that was calling CQ so I thought I would give them a go. Prior to calling my SWR on the loop antenna was tuned to 1.2:1 BUT when I started to call the Dutch station my SWR readout on the K3 magically became 99.9:1!!! It was like the coax had been removed from the antenna and was sitting on the ground. It was late so I wanted to look into this at a later time, this evening was the later time so I hooked the antenna up and gave 20m a go and the SWR once again on the K3 was showing 99.9:1. It was time to trouble shoot, was it the coax, MFJ 1788 antenna, the K3 or my LDG antenna switch? The first thing I wanted to do was to remove the antenna as the problem.
Without LDG antenna switch
I removed the coax from the antenna and in it's place put a 50 ohm dummy load. In a way I was relieved to see the 99.9:1 SWR thus removing the MFJ 1788 from the problem. Next I bypassed the LDG antenna switch and low and behold the SWR now was 1.1:1 and me saying thank god it was not my K3! So it would seem the LDG  antenna switch is the problem so I took the switch cover off and looked around. I cleaned the SO-239 connectors, check the internal connections and all seemed to be great. The only problem spot to me could be the switching relays with internal contact troubles? After exercising the relays the trouble in the LDG antenna switch seemed to be ok. If the trouble comes back this is a 4 position switch and I only use 2 positions I could swap out relays and look at ordering all new relays. At this point all seems to be working well but stay tuned to see if relay swapping and ordering is in the near future.
Relay in the LDG antenna switch

6 comments:

  1. Hi Mike, I wonder if you did work the Dutch DX station. 73 Paul

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    1. Hi Paul nice to hear from you. I was on but did not hear any Dutch stations.
      73 Mike

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    2. Well , I thought you did. "BUT when I started to call the Dutch station my SWR readout on the K3 magically became 99.9:1!!!" 73 Paul

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    3. Yes sorry Paul, I did hear the Dutch station but did not work him. I have just finished reading Bas blog about the Dutch contest and for some reason I thought you were asking me if I heard any Dutch contest stations.
      Mike

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  2. 99.9 to 1 with 5 watts? Now that's a mismatch! Running indoor equipment, it's sure easier to troubleshoot and find problem areas. I miss my tower but sometimes finding a problem was a bit tedious. I've had a few switches fail in the same manner. Keep at it! 72, Mike. de Phil AK7DD

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    1. Good evening Phil, for some reason your comment was in the hold section and I did not see it. It seems to be the relay on my antenna switch and I was told that tapping the relay may solve the problem when it acts up? I would rather change the relay so I took the cover off the antenna switch to see if it's the relay and then change it out……but since then the trouble has not surfaced……go figure! Thanks for stopping by Phil and sorry about the late reply.
      Mike

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