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Old April 21st 17, 06:51 PM posted to rec.radio.amateur.antenna
Fred McKenzie Fred McKenzie is offline
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First recorded activity by RadioBanter: Jul 2006
Posts: 317
Default Antenna for Marine VHF

In article , rickman
wrote:

A kayaking friend was asking me about antennas for marine VHF radios.
Someone recommended this type of antenna.

http://www.amateurradio.bz/2m-70cm_v...e_antenna.html

I guess my first question is what would this be dual band? Is it
because it works over a range from 2 meters to 70 cm? Or is it somehow
tuned for both bands at the same time but not a lot in between?

This antenna would need to be vertically mounted, so would be a little
clumsy sticking three foot up from a kayak. Light weight would be
better than heavier. The construction plans call for stainless steel
material. Any reason to not use aluminum? Is diameter important? To
use aluminum I would want to use something thicker than 1/8 inch and
likely hollow. I believe TV antennas are usually made from 1/4 inch
tubing with maybe 1/16 inch thick walls. I guess that might make it
harder to bend without kinking. Would it be ok to make it with some
sort of couplers for the bends?


Rick-

I did not watch the video. I believe the antenna is "dual band" because
it happens to also work on a frequency band that is three times the
basic frequency. In other words, 146 and 440. That does not appear to
make any difference with regard to the Marine VHF band. You would
simply scale the dimensions by the ratio of the Two Meter frequency to
the Marine band frequency, 146/156.

That said, the antenna in the article does not appear to be the best
choice for your application. The "J-Pole" antenna Jeff suggested would
be my choice. Do some research on the J-Pole, but remember to design it
for 156 instead of 146 MHz.

Fred
K4DII