Phone buzz through stereo

dan_b

A2OC Donor
Can anyone suggest a solution?
Sometimes, when I'm using my hands free system (Fiscon Bluetooth through the RNS-E with the hidden microphone) and making or receiving a phone call, depending upon where the phone is located in the car, I get a loud buzzing picked up in the speakers of the GSM phone signal.
I have to put the phone in strange places (e.g. on the floor) to stop the buzz.

Any suggestions as to how I can suppress the signal interference?
 
Try wrapping the cables that connect the handsfree with the RNS with some shielding?
Is it the regular chatter when the phone talks to base stations or a more continuous noise.
If you have a recent phone you could try limiting the phone to using the 3G and/or 4G networks to see if this helps.
 
What type of material would be a useful shielding? Do you mean between the Bluetooth module and the RNS, or between the handfree microphone and the RNS?
It's a continuous buzz once the connection is established.
 
Often shielding is just aluminium foil wrapped round the cables. Similarly some interference is removed by twisting the cables such as in network cable.
I was "thinking out loud" in my post. It is just the usual cause of this kind of issues. It may also help to check the earths on the stereo and see if there is an earthing plug on the Bluetooth module.
If there are additional earthing points on the units try connecting them.

I remember seeing an aerosol spray can of shielding spray for cables once that may be useful.

Other than the interference does the system work perfectly? If there are any other oddities it may be a loose connector somewhere.

I would suspect that the most likely place for the interference would be the microphone wires. Could you disconnect them at the RNS end and test?

John
 
Thanks. There is another odd symptom which is that people on the other end of the call say they hear a phantom echo - their own voice about 1 second after they've spoken. This didn't used to happen on my Galaxy S3, but does on the S5. I've tried switching off the phone's "digital noise reduction" option so we'll see if that makes a difference. Still can't get Music Over Bluetooth to work either, but less bothered by that at the moment with 64GB of MP3s sitting on my memory cards!
 
So the problem only occurred after upgrading to the S5?
Is the S5 on a 4G enabled contract? If so this could be the issue. There were/are issues between 4G and Freeview and so it may be that the interference is 4G related. Try the disable data connection toggle on your phone and see if the problem goes away.
 
Two things have happened at around the same time - I've changed phone, but we've also re-located the microphone - initially it was a clip-on job on the side of the A-pillar, but it's now fully integrated (hidden!) into the OSS control console.
 
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