[OT] DIY Antenna

Hans Fugal hans at fugal.net
Fri Dec 28 10:30:53 MST 2007


I know there are a few HAM operators here, and others who might have
some insight into my question.

I got a handheld radio scanner for Christmas, which I intend to use
almost exclusively for listening to aircraft communications (108MHz to
137MHz, especially 118MHz to 137MHz). It works great, but I would like
to try my hand at making an antenna to improve reception. The included
antenna is only about a foot long, and my understanding is that 1/4
wavelength for this band is about 2 feet.

The manual says "use 50-ohm, RG-58, or RG-8 coaxial cable to connect an
outdoor antenna". The connector is BNC. I've done some reading on the
'tubes' and would like to run my ideas by someone who has some
experience.

I reckon I could use a telescoping FM antenna at 1/4 wavelength (abt 22
inches). I'm not sure how to go about connecting it to the BNC connector
but that's probably straightforward given the right adapter, right?

I think maybe a dipole or folded dipole could do better. At least it
seems that way from what I've read. I've seen stuff saying folded dipole
has a wider bandwidth, which sounds good. But maybe the bandwidth of a
regular dipole is sufficient for the 20MHz-wide band in question. As I
understand it, a dipole antenna is about 75 ohms and a folded dipole is
about 300 ohms. Will I need a balun? What if I don't have a balun?

Thanks!

-- 
Hans Fugal ; http://hans.fugal.net
 
There's nothing remarkable about it. All one has to do is hit the 
right keys at the right time and the instrument plays itself.
    -- Johann Sebastian Bach



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