FM Radio J-Pole plans.

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Thursday, September 20, 2012

Weak station 100.7






In my rural location the only news talk station (100.7) is twenty miles away with, you guessed it, about a twenty mile range. This pathetic station has a 10,000 watt transmitter in a hilly heavily wooded area. I've tried several normal FM radio antennas with marginal success. I have decided to build a seven foot tall 1/2 rigid copper tubing (water pipe) antenna by cutting and soldering to specs for this frequency. The biggest problem here is supporting this on the antenna mast. The first thing I did to help was to slide an eight foot long wooden dowel inside the pipe after soldering. I then drilled out some 1/2 in CPVC tee connectors so they will slide over the pipe. At the top of the short side of the "J" I glued a little bridge to the long side for support. I glued on a 3/4 inch CPVC adapter and a short piece of 3/4" pipe with 1/2" EMT steel electrical tubing pressed in a couple of inches. The plastic connectors keep the antenna insulated from the mast while giving it support in three places.  Once in position I will drill and secure each tee with a SS  screw. The EMT will be welded to the flat bar on the U-bolt that attaches to the antenna mast. Look online for a J-Pole calculator, there are several good ones. I punched in 100.7 MHz since this is my problem station. Of course everything from 88-107 will come in as well, 100.7 should be the optimum for this antenna. Buy a piece of good solid copper coax cable so you can solder the center wire to the long side A, and the braid to the short side B. Attach at the feed point 2 3/4" up from the bottom of the "J" with a TV type "balun" matching transformer (Radio Shack etc.) . From there I recommend the cable go to a ground block before entering any structure, lightning is not our friend, hopefully any electrical problem will discharge to the ground. I should have this installed in the next few weeks and will update with the results. Check the comments for links to some other things I have built.

4 comments:

  1. Check out a related build of a GMRS UHF radio J-Pole.

    http://j-polegmrsuhfradio462mhz.blogspot.com

    ReplyDelete
  2. Check out a related build of a Gray-Hoverman UHF TV antenna:
    http://uhfantenna.blogspot.com

    ReplyDelete
  3. Bose 321 system modification:
    http://bose321speakers.blogspot.com

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  4. Finally got time to find a bad coax crimp at the antenna, corrected it and ran all new coax inside the metal building to radio. The old weak sister 100.7 sounds great and I get dozens of FM stations I didn't know existed.

    ReplyDelete