FM radio aerial: use TV coaxial cable?

[mike004]

Can I use my existing roof-mounted TV aerial as an FM radio aerial for my hi-fi? FM sockets in B&Q etc. seem to have the same coaxial cable connectors as TV sockets.

My hi-fi has a cheapo FM twin-wire T-aerial (fix to a wall). It connects on the back of the hi-fi via 2 cable-clamps for thin wires, not via a conventional coax cable socket. Can I easily use such connectors so that they connect to a coax cable and then plug into a conventional coax socket at the wall.

Thanks
Mike

 

[kendor]

the impedance is different 50 and 75 ohm but in saying that i have seen installs work ok especially as audio is more forgiving than oictures.

 

[mike004]

Thanks for your reply.

Is it just a simple matter of fitting a Y-splitter in the loft, taking one half to the TV and the other to the FM radio?

Mike

 

[Diyisfun]

Why not install an fm aerial in the loft, then use your exsisting down lead, with a Y spitter at each end.

 

[mike004]

The Hi-Fi and TV are at opposite ends of the room but both have coax runs coming thru the wall nearby. So a Y-splitter in the loft would be the quickest fix.

So, do I need a separate aerial for FM radio? I have seen set-top aerials advertised that claim to receive both FM and TV...
Mike

 

[Diyisfun]

If you are in lodgins then do what is easiest, if you are in a permanent residence, install FM aerial..........There is a difference..in HISS..but it depends what stations you are trying to listen to.

 

[ban-all-sheds]

I get excellent results from my TV aerial, same bit of co-ax, and one of those TV/FM splitter faceplates.

I guess it will always depend on the signal strength and tuner quality.

Those splitters are cheap and easy to fix, and don't need any fiddling around with aerials and duplexers, so if there's a TV outlet by the tuner, I'd say SIAS.

Whatever you do your biggest challenge will be to connect co-ax to a tuner which uses that twin cable aerial. There will be an impedance mismatch (I thought that those USA style 'T's were 100 ohms, but kendor could equally well be right) and termination issues.

 

[mike004]

>Whatever you do your biggest challenge will be to connect co-ax to a tuner which uses that twin cable aerial. There will be an impedance mismatch (I thought that those USA style 'T's were 100 ohms, but kendor could equally well be right) and termination issues.<

Yes. AFAIK, flat ribbon aerials are 300 ohms, coax is 75 ohms.
Plus there is the big problem of converting from coax socket to 2 x "piano key" wire traps at the back of the Hi-Fi.

Mike

 

[Steve]

I have seen co-ax joined to normal cable just by bundling the co-ax into a strand and using a connector block and tape to join it. This was on a CCTV system, for connecting a little 7inch LCD behind a checkout which had an S-video plug on it. I suppose if this works on CCTV pictures, it should work on FM.

 

[ban-all-sheds]

http://www.maplin.co.uk/Module.aspx?ModuleNo=5145&TabID=1

 

[Steve]

or you could use one of those

 

[mapj1]

Actually you don't even need to buy the FM aerial if you are feeling tight, and it can usually go in in the loft. A 1.5m bamboo rod, and two 75cm lengths of any old wire taped to it, with the coax going to the centre, and the centre wire going to one limb and the braid to the other will produce a dipole with an efficiency to rival the best you can buy (i.e. a typical 5 minute bellwire and bamboo lashup will give measured >90% efficiancy over an ideal dipole at 100MHz.)
Hang it broadside to the FM transmitter you most like, keeping it away from house wiring that might carry interferacne and listen to the signal roll in. Only if you are in a very marginal area for radio coverage do you need an outside aerial - the attenuation of roof tiles at VHF (radio) is much less than for TV (UHF).
TV coax will be fine, but if you want a good job void the cheapest stuff with wil-o the whisp braid - its not well screened and interference pick up can be a problem.

 

[AdamW]

A 1.5m bamboo rod,

Map, SURELY you mean a 1.53m rod (FM is 88-108MHz, so would make more sense to tune the dipole for 98MHz)

Sorry, I'll go back to bed now

 

[mapj1]

I've done it several times, at an average cost of about 50p an antenna its not worth bringing with when you move out - I've never found it particularly critical in respect of length... go back to bed!

 

[osmodia]

Hi,
I Have a 75 ohm coax aerial socket on my radio and am going to stick the 1.5 m antenna in the loft, The only worry is I will have to use about 9 m of coax to get to the right place AND 2.5M of that is to go alongside heating pipes (the only way up). Am I likely to get any interferance problems?