Sunday, July 24, 2011

Attic antenna ghost busters!!!

The SEP ARC plug
In an earlier post I described how I was having SWR issues (Attic antenna ghosts)with my Alpha Delta DX-EE antenna in the attic. When I put the ohm meter across the antenna feed (LMR-400 coax) I was getting 12 mega ohms.  I sent a post out on the Yahoo group ham-antenna   over time there seemed to be a consensus coming in that it may be the SEP Arc plug   causing the troubles. This device is across both legs of the antenna and is meant to look after any static troubles that may come upon the antenna. The problem I may be having is due to a high SWR on some bands and the SEP may be breaking down and giving me a high resistance short across the legs of the dipole. This made sense, so it was off to the attic

SEP ARC plug removed
to cut out the SEP ARC plug. After doing so I checked the antenna and the SWR was down just a little but not much. Again I checked the coax with the ohm meter and the 12 mega ohms was there!! Up to the attic I went AGAIN and removed the LMR-400 and tested the length of coax only...all was well.  I then tested the SO-259 and it was good???? When the LMR-400 was then again connected up to the antenna the 12 mega ohms returned. My conclusion is there must be some type of coupling that is happening in the attic. Never had this before..... but I do now, in all fairness I have never had a large antenna in the attic like the DX-EE. After removing the SEP ARC plug the SWR has never had the large swings as it did in the past. The only band that is giving me troubles now is 20 meters. The highest SWR there now is 2.45 and the tuner in the K3 looks after that just fine. I am just going to leave it and spend my time hamming it up!!!  


  1. Hey, sounds like you are a candidate for that haunted house ghost-searchers program on one of the American cable channels. You know, the one where they say "what was that!, did you see/hear that!" I love it when they go to a foreign country with a "haunted" site from the 14th century, then ask, in 21st century "American", the "spirit"to reveal itself.

    Happy you have worked antenna matters out. 73 Dick

  2. Yes Dick it has been some adventure for sure but now I hope it is all sorted out and I can get on wit hamming!

  3. Mike,

    I'm betting your coax run is under 50 feet if it's up in the attic. At most on 14 MHz you're going to have .3 dB loss at SWR 2.45, so, yeah, why worry about it! Glad it has settled down now.

    73, Casey

  4. Hi Casey, yes my coax run is about 30 feet max so the lose will be very little. So it is time to ham it up now and enjoy the antenna.

  5. Hi Mike, I had poor SWR results once with my equipement. Cause: an antenna switch was defect. I thought it was the antenna itself. Hi. I hope your problem is solved now. 73 Paul

  6. Keep up the good work, Im sure youll manage to get 20m sorted

    73, Lisa EI9GSB