Phone charging messes with radio reception?

[flcruising]

Just bought the wife a Griffin Powerjolt dual micro usb charger. When the phone is connected to it, the radio reception goes to crap. Unplugging the phone but leaving the cable and charger in place doesn't effect it. What gives? How do you even start to address something like this?

 

[kw_da]

Easiest thing to do, try another USB charger.

When you say radio reception goes to crap - what exactly do you mean? A lot of static or unable to pickup stations? Are both AM & FM affected? If you play music from a CD, is it also affected? This should determine if the problem is noise on the power line or RF interference. My guess is that when the charger is charging the phone it is emitting RF noise - it should affect AM differently than FM.

 

[Secondtyme]

Which means an RF filter on the power side of the charger would fix it, correct?

 

[kw_da]

I'm not a expert by any means, but my guess would be that the charger is creating noise on the power input, which then acts as an antenna and this broadcast interferes with the reception. If this was the case, putting an RF filter on the power cable such as a ferrite bead should filter the noise out, as Secondtyme pointed out.

If the charger is putting noise on the output, the connection from the charger to the phone is the antenna, and you would need to filter the output of the USB charger.

Hopefully someone with more RF experience will chime in

 

[flcruising]

So you're saying it's the cheap ebay usb cord? But then, even our oem phone cables don't have ferrite cores on them.

By crap, I mean that the radio has virtually no reception from otherwise strong stations. Unplug the phone and it all comes back. It's not isolated to a specific one either, 88.5, 91.7, 95.7 FM are frequencies we listen to and they all exhibited this behavior.

Honestly, this is the first usb car charger we've used in this vehicle, and we don't have any dedicated car chargers for our phones.

 

[DougNuts]

Hmm.....I only run into this when charging the phone and listening to AUX (with phone).

 

[kw_da]

If you put your phone into "airplane mode", does the radio reception come back? If so, the interference is probably not radiated from the phone, but is thru one of the cords acting as an antenna.

I can't remember, but isn't there another power plug in the back right side? If you plug your charger into this plug, does the interference go away/change?

Another thought - do you have an aftermarket radio? If so, are you sure it is grounded properly?

So you're saying it's the cheap ebay usb cord? But then, even our oem phone cables don't have ferrite cores on them.

By crap, I mean that the radio has virtually no reception from otherwise strong stations. Unplug the phone and it all comes back. It's not isolated to a specific one either, 88.5, 91.7, 95.7 FM are frequencies we listen to and they all exhibited this behavior.

Honestly, this is the first usb car charger we've used in this vehicle, and we don't have any dedicated car chargers for our phones.

 

[flcruising]

It's the oem 6-disc radio. I have the same charger/cable combo in my car and it doesn't exhibit this behavior for my oem radio, though it's a different phone too. We were not plugging into the aux input at the time either.

I'll do some testing and get back to you - cable, phone, airplane mode, charger, location, etc...

 

[Silentnoise713]

I think you must have come across a secreat agent gadget contraptions!.. Try another charger. I'm using a cheapie dual USB charger and works as designed (charging two devices). I'm also stock '08 GT radio. I also think it has to do with the cable acting as an antenna in the charger. If you plug in another USB power device other than a phone, do you get interference?

Hmm.....I only run into this when charging the phone and listening to AUX (with phone).

This is due to Mazda's poor ground. You can add (hardwire or external) a ground loop isolator to filter out the noise. The OP has reception interference, which is weird.