FM transmitter blocking sat nav signals?

  Diodorus Siculus 08:21 16 Oct 2007

I have a TomTom One XL (WE) sat nav system which guided me across France, Belgium and Holland wonderfully. For the last few weeks however, it was unable to get a signal most of the time when I would go on a long journey so TomTom suggested a hard reset, updating of software etc. but this was all to no avail.

Last night I realised that the inability to get a signal was due to my FM transmitter for my MP3 player (I listen to a lot of audio books when on the road). Whenever the transmitter was on, the signal could not be found or alternatively if the sat nav was on first, the signal would then be lost.

Does this make any sense and if so, what can I do other than forget about the transmitter?

Many thanks, Dio

  sinbads 08:46 16 Oct 2007

Is it not possible to use an external aerial?

  Diodorus Siculus 08:47 16 Oct 2007

Yes it is possible but not really a road I want to go down unless there is no alternative.

  sinbads 08:48 16 Oct 2007
  Diodorus Siculus 08:52 16 Oct 2007

Thanks but I have an external aerial - what I want to find out is if there is a way to avoid this and if the FM transmitter should be blocking the signal.

Perhaps it is the transmitter which needs replacing - I just want to find out if anyone else has similar problems.

  Graham. 09:06 16 Oct 2007

The FM transmitter is undoubtedly so powerful that it is masking the satellite signals, which are relatively very weak.

  sinbads 09:10 16 Oct 2007

Its obvious the transmitter is interferring with your sat nav as you say you loose the satilite connection whenever your tranmitter is on.

you are basically in a faraday's cage (surrounded by metal)) your tom tom only has the windows to get a signal, if the frequencies are simular then this is why its affecting your TT.

You get the same effect when usingg wireless routers and cordless phones. whilst both of your signals are in close proximetry, I would think your only options are and i,m not sure how you would do this ... change the transmitter frequency use some kind of filter.

  muddypaws 09:11 16 Oct 2007

My son has just got the TT 720. Not sure if he has set up his fm transmitter link yet. If you leave post open for a couple of days will try and check.
Have you tried the TT forum yet? click here

  jack 09:30 16 Oct 2007

Is possible to re-site the transmitter to another location on the car?
TT is an audio/viual device I know but I guess you could get by with audio only- "turn left 'ere guv!"
at a pinch thus re positioning the TT ;->

  FatboySlim71 09:34 16 Oct 2007

Has your car got a heated front windscreen?

The reason I ask is, I used a sat nav in a hirecar that had an heated front windscreen and I was unable to get a signal, the heated front screen does not even need to be turned on for it to block the sat signals either, once I moved the sat nav on to the passenger side window everything worked fine.

  octal 10:00 16 Oct 2007

The FM transmitter is putting out harmonics of the original signal. It should be filtered, but it's obviously not and at least one, possible a group of harmonics are ending up in the satellite band.

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