Radio Interference

[travelrover]

Hi all

I recently ran a power cable from the fuse box to my overhead console via the passenger side A pillar and mounted a connector with 2 USB ports on it behind the two way radios.

It runs from an empty slot next to the radio fuse (1999 TD5 which I have owned from new) and only has power with the ignition on.

This is to power dash cam/go pro/GPS and the like rather than having cables dangling all over the place and it works well. Well, expect in areas where there is poorish radio coverage (FM Commercial stuff) and there are lots of those around where i live I get interference on the radio. Unplug the the dash cam or turn the engine off and all is back to normal.

The new power cable doesn't run anywhere near the FM radio or coax cable (other side of the vehicle) and the earth is good.

Am at a bit of a loss just now. Any clues as to what may be the cause the interference?

Cheers - Simon

[Tombie]

Where did you Earth it?

[Dorian]

You will probably find that it's your 12V to USB charger that is at fault.
I first noticed that I had this problem in my puma when charging my IPhone, particularly when I left the phone in the USB system once it was fully charged. Was ready to blame Apple, but found the same problem with my friends Samsung, so the USB charger was the common item. Although my problem was less about loss of reception and more about noise on the audio. I checked and upgraded my earthing several times to no avail.
I have something like this mounted in my dash.

Dual USB CAR Cigarette Lighter Socket Splitter 12V Charger Power Adapter Outlet | eBay (http://www.ebay.com.au/itm/Dual-USB-Car-Cigarette-Lighter-Socket-Splitter-12V-Charger-Power-Adapter-Outlet-/371655328341?hash=item5688624255:g:djAAAOSwc1FXX-1s)

If you google something like "usb charger causes radio interference" you will get a heap of hits.

I think it's because the 5Vdc side of the lower quality USB chargers don't have a capacitor/diode suppressor across the switch mode power supply. I was able to fix most of my problems by wiring all of the USB chargers from the house battery rather than from the Aux. This seems to suppress most of the noise on the 12V end.

If you really want to enhance this noise, charge up your phone to full, leave it in the USB charger and plug in the 3.5mm audio jack from the phone to the Aux on the stereo. This seems to set up a pretty viscous techno pop beat in my car.

The upside of powering from the house battery is that you can charge stuff up when the engine is off. The down side is that the USB chargers will try to drain the house battery down to 5V. Which means that you need another VSR between the house battery and the USB system.

If you want to stay powered from the Aux, I'd suggest that you try running the 12V to your USB thru a suppressor and keep the suppressor close to the USB charger, this should stop the RF traveling back down the 12V system.
Sorry I don't have any recommendations as to the suppressor you would use but since it's electrically the same effect as a spark plug / coil, i'd try something like this

https://www.jaycar.com.au/10a-dc-noise-filter-improved/p/AA3074

or perhaps salvage a unit from the wreckers.

Cheers Glen

[travelrover]

Hi Tombie

It is earthed on the frame of the fuse box so should be fine. But i will look at moving that if further diagnosis reveals no improvement.

Hi Dorian

I have swapped out the USB socket, the first one I had looks just like the one in the link with the blue LED, the one I have now has no LED and is a better quality but the results are exactly the same.

So far I have only had a cheap ?no brand? dash cam from Supercheap plugged in so I will swap this for a ?branded? one we have of hopefully better quality and see if this is the root cause. I have not plugged in any other types devices yet so this will be my next cause of action if no improvement.

Thanks both so much for your assistance.

Cheers

Simon :p