single
Well-Known Member
My FM aeriel is currently a single wire 62cm long but the reception is rubbish.All i know about aeriels is something to do with the size is critical so can i modify it?Any suggestions that i can easilly make now?
FM aeriel
- Thread starter single
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vyv_cox
Well-Known Member
62cm may be a little short. Mine is about 2 metres and works well. You often need to find an interference free location where it will work well. Mine lies along the lockers behind the saloon seats
KellysEye
Well-Known Member
We fitted a modern car aerial at the top of the mizzen mast, it worked well.
rob2
Well-Known Member
Sounds ideal, but a mizzen mast is probably beyond the budget of a man who wants to know what length of wire will do! At the risk of stating another row, I use a splitter so as to use the masthead aerial. I would suggest that if you went this route, put the splitter right by the VHF so you can plug the aerial directly into it if you're wanting to use the VHF in anger when a significant distance offshore. I've known people to use a couple of meters of wire and some even connect to a chainplate so the whole rig becomes an antenna. I believe that height is an advantage, particularly if you're in a marina where the surrounding masts can be almost as effective as a Farraday cage at masking the signal!
Rob.
single
Well-Known Member
I have a mizzen but loads of hassle.Anyway this has worked.I just put a single strand straight to the outer sleeve of vhf and its fine (both vhf and fm!) cool.
William_H
Well-Known Member
Well in answer to the OP the ideal length of a 1/4 w wavelength at 100mhz is about 30 inches. Google will give exact for your favourite station. You should have a ground plane of 3 or 4 wires similar length from the shield of the cable laying in the opposite direction to the actual aerial. The aerial should be vertical. As said however even the perfect aerial (and it doesn't matter much for receive) is no good unless it is high up. So try to get as much height as possible. good luck olewill
elton
Well-Known Member
What happens when you transmit? Does your radio or the VHF explode?
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single
Well-Known Member
Not yet.....should it?
Puggy
Well-Known Member
I realise that the OP is probably looking for a simple, cheap solution, but FWIW I bought a small Glomex omnidirectional TV aerial: not the usual ugly flat ones, but a much smaller vertical one VT300 and this has a TV/FM splitter. I am surprised how well it works for both TV and FM, especially as the aerial is lying under the aft berth in my boat as I have not yet been brave enough to climb the mizzen mast as I am not convinced it is strong enough to hold my 100kgs..
elton
Well-Known Member
I couldn't say, but I very much doubt the aerial input of your FM radio is designed to take a direct connection of the 25 Watt output of your VHF transmitter. I wouldn't even try it, so I'd be interested to know how it works out. If it does work, I'd be interested to know how it affects the range of transmission.
Or it's possible I've completely misunderstood what you're doing.
Rigger Mortice
N/A
As I read it, the FM aerial is completely separate from the VHF.
rob2
Well-Known Member
I do hope so! The thought of operating a VHF transmitter down a short length of wire might be amusing to us, but it will warm the wallet of many a chandler. (It just so happens that "Open All Hours" is on the telly, right now).
Rob.
single
Well-Known Member
The FM single wire is just jammed on the outer sleve of the vhf bnc connector.
dmayes
Well-Known Member
The formula for finding a full wavelength is the speed of radio at 300,000,000 meters per second divided by the frequency of the radio wave. Hence the length of a marine VHF is 300 divided by 156 (about 2 meters) for a full wave length, the whip aerial is a half wave so approx 1 meter in length. Same formual can be applied to FM radio. 100 MHz half wave would be about 1.5 meters long.
Rigger Mortice
N/A
If the wire is connected (electrically) to the screen of the VHF cable it might be worth disconnecting it. A one minute job which might improve things.
David2452
Well-Known Member
I've had some success by simply connecting the lead to the bottom of a stanction if accessable.
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