Tuesday, June 17, 2014

Oz Report's Antenna

2m (144-148 mHz) Antenna with molded BNC connectors (the only kind worth anything in hang gliding harnesses).  

Five foot long total RG58C/U coaxial cable. 19.5" of unshielded center cable (for 144-148 meters) which you attach to your harness mains (using tape).

The ground wire is the exposed shielding wire, the mesh wire that normally surrounds the interior wire. This is how you hook it up in your harness: http://sahga.com/harness_antenna_2.gif.  

You can just tape down the braid also.

I have also had adequate success just cutting off the braid exposed ground line like this:

Click on above to view a higher resolution image. 

Connect the antenna, as shown in the diagram above, to your mains. I suggest in a manner to protect the junction at the end of the shielding from flexing, so run the shielding up the mains for a couple of inches, if you have the room. 

I have normally cut off the ground as it is sometimes a bit of a hassle to place horizontally along the back plate, but by leaving it on you have better matching of your antenna to your radio to get the highest signal power output. I've had good luck even with the ground gone.

The antenna is cut to 19.5 inches which corresponds to 144 mhz. You can cut the antenna a bit shorter for high frequencies if you like, although the differences are quite small. To know how long to cut the antenna (the single center strand), it is length (in inches) = 2808/freq in mHz. For example, for 147 mHz, length equals = 2808/147 = 19.1 inches.

No comments:

Post a Comment