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Posted: 9/11/2013 11:41:36 PM EDT
So, I've got a Cobra MR HH425LI VP radio (Marine VHF and GMRS) and am trying to learn if it's possible to make a dual-band J-pole that will serve both bands well. My inspiration are the various Arrow Antenna Open Stub J-Poles. I'm as dumb as a stump when it comes to the science behind antennas, I just know that the 155/460 MHz Arrow Antenna I got works quite well for Marine VHF, but quite poorly for GMRS (which, I understand is no fault of the manufacturer since it wasn't designed for GMRS). Is there some specific harmony between the two bands selected for each antenna, or could I just have one element tuned for 157 MHz and another for 462 MHz?
Link Posted: 9/12/2013 1:40:25 AM EDT
Very easy to do. Just get some TV twin lead and cut it for the appropriate frequency.
Link Posted: 9/12/2013 3:40:48 AM EDT
http://www.mtcradio.com/blackbird-vhf-uhf-jpole-base-antenna-mar-gmrs/

This is close.

Gmrs is almost a harmonic of the marine band so a vhf antenna may present a good swr, however radiation patterns might be crazy. Look for the QST article by Ed Fong on his dual band jpole to see what I am talking about.
Link Posted: 9/12/2013 2:39:53 PM EDT
Quoted:
So, I've got a Cobra MR HH425LI VP radio (Marine VHF and GMRS) and am trying to learn if it's possible to make a dual-band J-pole that will serve both bands well. My inspiration are the various Arrow Antenna Open Stub J-Poles. I'm as dumb as a stump when it comes to the science behind antennas, I just know that the 155/460 MHz Arrow Antenna I got works quite well for Marine VHF, but quite poorly for GMRS (which, I understand is no fault of the manufacturer since it wasn't designed for GMRS). Is there some specific harmony between the two bands selected for each antenna, or could I just have one element tuned for 157 MHz and another for 462 MHz?
View Quote

A 460 antenna should work perfectly for GMRS.
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