TomTom 740 Interfering with Car Stereo

[ajkidle]

As much as I love the TomTom 740, the buzzing dit-dit-dit-dit-dit interference that comes through my car speakers (2006 Toyota Highlander) every couple of minutes is driving me nuts. Happens anytime the stereo is on (CDs or radio.) I've tried turning off Bluetooth, no help. I'm wondering if it's the LIVE services through the cell network causing the interference.

Anyone else experience this, or have ideas for a solution?

 

[mvl]

This is standard experience with GSM cell phone technology. If you've been using Verizon or Sprint (CDMA), you may have not experienced this in the past.

The Tomtom uses AT&T, and you'll have the same thing happen with AT&T cell phones.

I've noticed that this doesn't happen to newer cars very often. Perhaps there's better shielding in radios. Maybe someone here with more experience in radio/speaker shielding knows a way to help workaround the situation.

 

[mikealder]

Try moving the device to a different location on the windscreen as close proximity to the radio unit can make this worse.
Also depending upon where you are relative to the GSM transmitter masts will have a bearing on this, the further away you are the more power the GSM module will use for communication, this is normal and there is nothing you can do about it.
One thing you can do is add a screen mesh / foil around the wiring to the stereo, this will sheild the wiring from the interference reducing the induced noise, make sure you connect the sheild/ screen to the cars bodywork or negative terminal on the radio - Mike

 

[jmorisey]

Try moving the device to a different location on the windscreen as close proximity to the radio unit can make this worse.
Also depending upon where you are relative to the GSM transmitter masts will have a bearing on this, the further away you are the more power the GSM module will use for communication, this is normal and there is nothing you can do about it.
One thing you can do is add a screen mesh / foil around the wiring to the stereo, this will sheild the wiring from the interference reducing the induced noise, make sure you connect the sheild/ screen to the cars bodywork or negative terminal on the radio - Mike

Mike, I am not very technical when it comes to radios and RF, but my XM radio has "Ferrite Beads" on both the antenna and the power cord. If he purchased one of these "Ferrite Beads" from like radio shack or something, would that fix the problem?

(When I say "Ferrite Beads" I am referring to a little magnetic clip the wire wraps around.)
Ferrite bead - Wikipedia, the free encyclopedia


Jon

 

[paspossible]

What you ear is the GSM signal from the phone. It have nothing to do with the TomTom. The TomTom doesn't need to be in the car or even close for you to ear this. The difference is, when you have the TomTom connected to the phone to get the LIVE services, the phone is transmitting way more often and at stronger level than if it would be only in voice mode so, you will notice it more.

I suggest trying to move the phone. Often, 6 inches will make a difference. If the phone is right above/below the radio, there's your problem. Put the phone towards the back in the center console, in the door compartment, anywhere where you can safely reach it while it's as far away as possible from the radio/car antenna.

Also, sometimes it's the speaker wires that catch the signal. Trying to stay away from speakers might help.

Last, the stronger the phone transmit, the louder the sound will be. You could place the phone close to the car's roof, let's say on the sunvisor. This way, the phone have a clearer "view" of the radio signal so it will transmit at lower power. Don't do this if the radio antenna is in the front windshield: it could make the problem worst!

 

[mvl]

The 740 has a built-in GSM modem - so the interference could be from the phone's GSM transmitter or the 740's GSM transmitter.

 

[mikealder]

The x40 can produce quite impresive interference IF the vehicles stereo and associated wiring isn't well screened, I can hear mine creating noise from time to time depending upon where I put it in the vehicle - Keep it away from the head unit and speakers and its not too bad though - Mike

 

[paspossible]

The 740 has a built-in GSM modem - so the interference could be from the phone's GSM transmitter or the 740's GSM transmitter.

Sorry! I didn't know that!

How does it work? You need a subscription from a Mobile Carrier and the 740 is seen as a wireless cellular modem? Quite expensive on the long run if that's the way!

 

[mvl]

You pay Tomtom a subscription fee that includes the data costs and the LIVE services.

The 740 is a cellular modem, but Tomtom pays the cellco. In the US, the 740 uses AT&T's network, in the rest of the world, it uses Vodafone.

The only purpose for bluetooth would be handsfree pairing and phonebook transfer.