Thread: J Pole
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Old September 3rd 06, 09:13 PM posted to rec.radio.amateur.antenna
Dave Platt Dave Platt is offline
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First recorded activity by RadioBanter: Jul 2006
Posts: 464
Default J Pole

In article YoGKg.3053$CL6.2183@trnddc06,
Amerigo Vespucci wrote:

I don't have any 300 ohm twin leed and really(at this time) don't feel like
doing the copper pipe thing .Is there another easy way to make one.My
thoughts were to maybe take and attach some wires to a board say a 1x4 and
just make it work accordingly.


Sure, you can make that work. You'll need to fiddle with the lengths
of the elements, and the attachment point of the coax to the matching
section to get the best match. Using an MFJ or similar antenna
analyzer will make the job easier.

I built a J-pole somewhat like this by taping ordinary insulated
hookup wire to the fiberglass shaft of a bicycle safety flag. It took
a while to get the lengths and feedpoint position adjusted correctly,
but once it was done I had an antenna which was 1.5:1 or better across
the entire 2-meter band, and works very nicely when I ride "bicycle
mobile" at a public-service event.

If you aren't planning to transmit, you probably will have an easier
job of it - your scanner will work acceptably even with a significant
amount of mismatch at the antenna feedpoint.

I'd suggest thoroughly waterproofing whatever piece of wood you use -
treat it well with marine spar varnish or a similar outdoor-rated
polyurethane or other varnish. This will ensure that the wood doesn't
soak up rain moisture and change its electrical characteristics and
de-tune the antenna.

As another alternative, since you're scanning and would presumably
prefer a wide antenna bandwidth, would be to make yourself a skeleton
discone. A chunk of wood with holes drilled in it, and a dozen pieces
of stiff wire, and a bit of simple soldering and you'd end up with an
antenna which would probably receive acceptably over a very wide
bandwidth.

--
Dave Platt AE6EO
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