Thursday, July 17, 2008

Tinkering in Antennas

So all this simplex work lately just pleads for a better antenna.  My workhorse of an antenna is a copper J Pole made out of 1/2" copper tubing, which I'll write about later.  Right now I just want to express my frustration / surprise on the disconnect between SWR and performance.

SWR is the Standing Wave Ratio of an antenna.  As you go from one conductor to another (ie coax to antenna), some fraction of the radio energy is reflected back to the radio, which if bad enough can damage the radio.  It is every antenna designers dream to build an antenna with the longed after 1:1 SWR.

When I built my J Pole, I measured an SWR of 1.8:1, which is passable, yet not great.  Yesterday I slapped together a vanilla dipole using welding rod (whoever mentioned that in his article in the 60s was GENIUS), and first shot I got a 1.6:1.  Great!  An antenna that not only scores better than my J Pole, but is directional too!

Yes, and no.  It is directional.  I can hit a repeater, rotate it 90 degrees, and not hit the repeater.  Good deal.  At the same time, I can plug my radio into the J Pole, and hit the repeater until the cows come home with at least a +1 S reading.  So a better SWR is better for your radio, but a better antenna is a better antenna is a better antenna.

I'm collecting the stock I need to build a Yagi, so we'll see if I can ever top my first attempt.

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