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On Fri, 21 Apr 2017 00:28:47 -0400, rickman wrote:
Starting over from scratch... A kayaking friend was asking me about antennas for marine VHF radios. What problem is your friend trying to solve? My guess(tm) is that he wants more range from what he's getting on his VHF marine handheld radio. This is a common problem because the typical rubber ducky helical antenna used on handheld radios has very low gain and is lacking a proper counterpoise. The first improvement would be to replace the rubber ducky antenna with a 1/4 wave vertical stiff wire antenna on 156Mhz. It would be about 48cm (18.9 in) long. That will provide a little gain and not be too long and unwieldy. There are various such antenna available that can be cut down to length. I would need to know the radio model and RF connector type in order to be more specific. Then next improvement would be a counterpoise ground element. In ham radio circles, it's called a "tiger tail". http://www.hamuniverse.com/htantennamod.html https://www.google.com/search?q=tiger+tail+antenna&tbm=isch It's just a length of 1/4 wave insulated wire dangling opposite the antenna element. You could get fancy and use 3 or 4 such counterpoise elements, but the improvement over a single element is minimal and not worth the effort. If the kayak was of a larger or ocean going variety, it might be possible to mount a larger marine antenna like this: http://www.n0lx.com/kayak.html It's for HF, but would serve as a suitable mount for a VHF antenna. A key component is the mount: https://www.westmarine.com/antenna-mounts I suggest something like this bolted to a backing plate: https://www.westmarine.com/buy/west-marine--dual-axis-ratchet-mount-nylon--1986645?recordNum=12 The thread fits most larger marine antennas. https://www.westmarine.com/vhf-antennas Light reading: "VHF Marine Antenna Fundamentals" http://www.boat-project.com/tutorials/vhfant.htm -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
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