Aerial for car stereo.

[Lee_Shaw]

Hi.

I've just fitted a stereo in my boat and I am wondering about an aerial for it (mw/lw/fm).

I was wondering if I could just connect it up with a coaxial to one of the shrouds via the chainplate or is there something magic about the piece of metal that makes up an aerial that would require me to use a commercially available product? Basically, am I missing something?

Also are there any other implications that I haven't thought of with this using a shroud idea.

Thanks in advance.

 

[fireball]

We just purchased a cheapo one from H*lf*rds and cabletied it upright in a tall locker.. reception is absolutely fine here ...

 

[fastjedi]

Yep, I thew one in some wasted space behind the seat cushions. Positioned horizonal and connected only by the cable .... worked fine. (If the stereo case in earthed so is the aerial)

 

[Evadne]

The magic things about an ariel are the earth plane and the length. For a car stereo, these are not critical, unless you want long range reception: my old cortina got Radio One in stereo with a slightly modified (bent) wire coathanger. The only thing I can think of being wrong with the shroud is if it is earthed, then you won't get much signal. A plain length of speaker wire does for us.
MW and LW ferrite ariels are inside the actual radio usually.

 

[cptshed]

I use one of those electronic ariels,fitted it behind a panel,works fine.Bought it
from a motorfactors, about £12.
Could use one of those rubber duck type ones,as suggested, stuff it behind a
panel or similar,should be no prob'.

Nige'

 

[peteandthira]

I use a splitter from the VHF aerial, but sometimes seems to give a weak signal in certain parts of the Clyde area. I have yet to work out if thats an aerial problem or an area problem.

Anybody else using a splitter? With or without satisfaction?

Pops

 

[Phoenix of Hamble]

I use a splitter as well, with no problems...... mine is switched, so I do have to remember to switch it to the correct setting before setting out to sea, but it works very well....

 

[Talbot]

if using a conventional car aerial, make sure that the aerial is earthed properly. This should happen through the radio case, but make sure that the the coax cable makes a good bond on the earth side as well as the actual aerial.

 

[pampas]

centre core of the coax to a 4500 micro farad electrolitic capacitor is all that is required. I now get stations that never recieved before /forums/images/graemlins/smile.gif.

 

[rwakeham]

I just put some co-ax cable under the head lining, bought a plug from Maplin and plugged it in the back of the stereo. I used 10m and I get all the stations I want.

 

[rutten]

I was told that using a splitter (on VHF) might damage your stereo. What is true about that?

 

[rutten]

how long is this coax cable; rwakeham writes 10 metres?

 

[William_H]

In an AWB (fibreglass) there is very little problem of shielding of the signal by the hull and very little interference compared to a car ignition etc. So you do not need as in a car an external aerial with tight shielding inside the car until it gets external. All you need is a piece of wire inside the hull. It does not need a shielded cable except that that is a convenient way to get a correct plug to go into the radio. If you use a piece of insulated wire you need to carefully feed it into the hole in the middle of the socket hole. It is about 3mm diameter. It is easiest to fold over 20mm of bare wire to make 10 mm bare to push into the hole and hopefully it will remain attached and not short to the inside of the socket body. For good FM reception you need about a metre of wire but for good LW and medium wave go for 3 or 4 metres laid inside a shelf or if possible under the headlining. If that does not perform well enough then look at a long external wire.
You could try the stay and mast but if there is any lightning around you may find the radio dies even without a direct strike. So it is best to earth the mast and stays for protection. olewill

 

[Lee_Shaw]

Thanks for the replies.

A length of cable inside the hull seems the simplest method so I'll do that. Don't like the sound of the lightening.

The radio actually seems to work in the marina with a 2 foot long piece of wire sticking out the back but for some reason I thought that there would be some advantage to having a large, high aerial. If not then I reckon I'll just go for a longer length of wire.

Thanks again

 

[Guest]

Best is cheap Rubber duck ....

Get hold of one of the 'replacement repair' rubber duck aerials ... it doesn't break when knocked / bent / hit etc. Has compensator to make up for its lack of length ...

Easy to fit on rail or even through transom deck etc.

 

[PhilipH]

What about on an aluminium boat?

 

[Ships_Cat]

On a metal boat, unless only want poor reception, then you need an external antenna. Do not use a car antenna as they use the mount as a connection to the metal it is fitted on as the groundplane (on a car the mount is normally shorted to the cars steel body) - that will lessen the integrity of your isolated negative 12v system as it will connect your hull to the chassis of the radio. Even if your 12 v system is not isolated from the hull, such an antenna will provide another possible leakage path back through the hull.

Glomex, among others, make am/fm antennas which are isolated from their mounts.

John