VHF antennae on a kayak mounted pole ?

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charleston14
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VHF antennae on a kayak mounted pole ?

Post by charleston14 » Sun Oct 07, 2018 10:14 pm

I’ve never seen one and so there’s probably a reason why but has anyone ever thought of increasing the range of a handheld marine vhf by having the antenna higher up?

E.g a boat mounted antenna ? ( For plugging in to in an emergency) In theory it should be possible to disconnect the short whip antenna and connect to a cable with an antenna at the top of a pole, eg at the top of a kayak sailing mast or similar extended device

Logic being that the higher up the antenna the better right ?

Chris Bolton
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Re: VHF antennae on a kayak mounted pole ?

Post by Chris Bolton » Sun Oct 07, 2018 10:20 pm

I've thought about it but never tried it. Possible problems are the difficulty of rolling with a mast up, so it would have to fold down, plus making electrical connections in the marine environment; it all gets a bit complicated! It's also worth considering what the limiting factor in VHF range is - is it the line of sight horizon or is it the power of a handheld transmitter? I don't know, but in most cases I'm either calling or listening to a Coastguard antenna mounted well above sea level, or (occasionally) another kayak within visual range.

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Re: VHF antennae on a kayak mounted pole ?

Post by andynormancx » Sun Oct 07, 2018 10:36 pm

The limiting factor is not the power of the transmitter. The limiting factors are line of sight and the antenna design.

With the right antenna and line of sight (i.e. both transmitter and receiver on top of big hill/mountain) a 5W handheld VHF radio can be heard 100 miles away or more.

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Re: VHF antennae on a kayak mounted pole ?

Post by andynormancx » Sun Oct 07, 2018 10:43 pm

But as you noted, raising the antenna a few feet when talking to the coast guard may well make little difference.

Say the radio is normally about 1 metre above sea level when you are in a kayak and the coast guard antenna is 50 metres ASL.

The radio horizon for the combined setup is 33km. Even if you raise the kayak antenna to 3 metres, the combined radio horizon only goes up to 36km.

All of that assumes flat ground/water between the kayak and the coast guard though. If your line of sight was blocked by relatively low stuff close to the kayak then you'd get more benefit.

http://www.vwlowen.co.uk/java/horizon.htm

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Re: VHF antennae on a kayak mounted pole ?

Post by PlymouthDamo » Sun Oct 07, 2018 11:38 pm

I wouldn't want a tall mast on my kayak as it would get damaged eventually. Would it be possible to keep a coil of antenna wire on you which you could screw into your VHF in place of the stumpy antenna when needed? Then you'd somehow fix the other end to your main paddle blade and hold it up, or fix it to the blade of your spare paddle which you'd slip down the back of your BA so it's permanently sticking up? Dragon's den anyone?

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Re: VHF antennae on a kayak mounted pole ?

Post by charleston14 » Mon Oct 08, 2018 5:26 pm

pop up kayak sailing mast with antenna on the top ..or an extending pole that engages into a fitting on the deck and secured by bungees.

Holding up a paddle might work, but attaching it to a paddler is perhaps a bit risky.

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Re: VHF antennae on a kayak mounted pole ?

Post by PeterG » Wed Oct 10, 2018 9:55 am

Handheld VHF can be very quirky, near the cliffs in Scotland sometimes someone 50m away in plain sight is out of range. On the other hand from the top of Butser Hill 270m you can hear the port traffic at Cherbourg 110 miles away. The handhelds have an aerial designed for all round use and not too affected by not being vertical. An aerial on a pole might be badly affected by our swaying on the sea.

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