Antenna for car type fm radio in a grp boat?

[Quandary]

Help please.
What is the best set up for radio reception( not vhf) on a grp hull. My last boat had an agriculture spec. (made for a tractor) cassette radio which in the same general sailing area, received on FM, Medium and Long Wave with just about 2m. of wiggly wire lying above the headlining. For my new Blaupunkt car stereo/ music player I have tried two car antennae, the first, a windscreen type from Bluespot the second a telescopic roof type antenna from Halfords, both give some reception on FM but nothing but noise on med. and long wave. Outside or inside the hull, the position of these antenna made little difference,( though I do keep the boat on the West Coast of Scotland where most reception is generally poor). The antenna fitting instructions tell you to make sure that they are bonded to the car body work, difficult when this is grp. I have tried running a cable from the mounting bolt back to the body of the radio but no difference. Since nearly everyone fits car type cd or sd card radios in boats there must be an easy answer?

 

[vyv_cox]

I would try it somewhere else, in your car for example, to see if there is a problem with the set. Could be something to do with its setup. My 'length of wiggly wire' picked up BBC on LW as far as Corsica and Five Live at least as far as the Gironde. It was far better than a purpose built car antenna, so I dumped them and kept the wire.

 

[philip_stevens]

I've got a similar set-up radio as you have, and it works fine with a Halfords car rubber-ducky aerial just hanging loose below deck near the radio.

 

[BobnLesley]

...it works fine with a Halfords car rubber-ducky aerial just hanging loose below deck near the radio.

Ours is 'temporarily' laid on a shelf in the forecabin and has been there for six years now; I thought it worked great until I saw vyv's post - we lost Radio 4 long wave at about Marseille.

 

[Quandary]

Ok ,if a bit of wiggly wire is the solution can someone give me a spec for it. What type of wire? coaxial? how best to connect to the antenna socket? I do know it can work from previous experience, I just don,t know how to replicate it. Or is their a technical answer?

 

[matelot]

Doesnt sound like an aerial issue so much as an electrical noise issue. Fridge? Engine noise?, inverter?

A car radio should pick up signals on MW using a length of wire stuffed into the socket at the back. OK thats not ideal but what I'm getting at is that if you are hearing nothing then you have an interference prob either inside the boat or from outside source. An aerial wont help if this is the case.

 

[ebbtide]

Re: Antenna for car type FM radio in a grp boat?

More please! Same car radio with powered interior aerial but Long Wave? Forget it, only faint burbling locally, less in France when I wanted Radio 4. So all suggestions welcomed.

 

[William_H]

Re: Antenna for car type FM radio in a grp boat?

An ideal antenna for MW/LW is a wire as long as possible preferably up the mast. You could try connecting to the rigging. However for VHF FM a wire about 1 metre long horizontal along a shelf is the correct length. However for better reception this wire should be up as high as possible with a coax cable feed.
I do tend to agree that your lack of reception may be an interference from the boat or nearby. Try turning everything off except the radio.

 

[Quandary]

I have investigated interference from fridge, charger etc. and it does not appear to be the problem, I am convinced it is weak reception. In a car the antenna must be grounded to the metal body, does this mean that the lw. mw. signal is picked up by the metal bodywork and fm. by the antenna? if so how best to replicate this on a boat. The antenna receives about 5 fm stations quite well and this does not seem to vary by antenna location or attitude. How can I add mw. lw. reception without compromising fm.?

 

[Quandary]

Just to add to above, our old portable radio receives all the stations we are looking for sitting on the chart table, maybe I should cannabalize it?

 

[William_H]

No the screen of the shielded cable is connected to the car body at the antenna and the radio to keep out the interference that abounds inside the car body.
Note that the cable is not coaxial cable though it looks like it but is a low capacitance screened cable. ("coaxial" cable usually means a cable of low characteristic impedance 50 or 75 ohms. car radio antenna cable is coaxial in construction but best described as shielded cable) The capacitance though lower is actually unwanted in the lower frequency circuits and is often taken into account by a small variable capacitor adjustable from outside the radio. (a hole with a screw at the bottom).

Anyway I suggest that for MW /LW you try a long wire (as long as is convenient) (or connect to the rigging) that is pushed into the antenna hole in the radio. Note this consists of connection on the outside for the screen and another hole for connection of the centre active wire. Use only the centre. You can make the wire fatter by folding to stay in the hole or use a "banana" plug as is often used on multimeters about 2.5 mm diameter.

Actually I am a great fan of the old style car radios with mechanical tuning and usually very good MW.LW performance. They don't have to be retuned after power has been off and/or don't need a keep tuned supply for when power is off. good luck olewill

 

[Graham_Wright]

On the recommendation of an ex-GCHQ friend (ex GCHQ not ex friend), I installed a spiral of ordinary single coil wire over the headlining. Works a treat but I don't know why.

 

[vyv_cox]

I was about to make virtually the same reply as you have done. The shielding is there simply because there is so much electrical interference in a car that is 'trapped' by the steel bodywork. I haven't tried it for years but in the past a transistor radio was useless in a car for this reason. In a GRP boat there is far less need for the shielding. My 'wiggly wire' is about 2-3 metres in length, just laid out along a couple of lockers. It's a bit of ordinary connecting wire that I had in my electrical bits box.

 

[st599]

[ QUOTE ]
On the recommendation of an ex-GCHQ friend (ex GCHQ not ex friend), I installed a spiral of ordinary single coil wire over the headlining. Works a treat but I don't know why.

[/ QUOTE ]

Possibly acting as a magentic wave antenna, rather than electrical - therefore less prone to interference from electrical non-radiating sources?