Charging iPhone in 12V Knocks Out Mobile Antenna?

[Dave_D]

File this under "Anything That CAN Happen...."

Last weekend, my wife and I ran our car in the annual Silver State Classic Challenge open road race in Ely, NV. It's our twelfth time running the event, so you'd think, by now, we'd have our technology in order. No way.

Minutes before approaching the starting line, we noticed that our Uniden BCT15 scanner had gone silent. The only change we had made to the vehicle was to ditch the 12V splitter as it was unnecessary - only my iPhone was plugged in. So, I unplugged the iPhone charging cable from the car's 12V receptacle and - surprise, surprise - the scanner popped back to life. Repeating the process verified that plugging the iPhone into the car's 12V receptacle was knocking out reception. Not all of it, but maybe 95% of it.

The only frequencies we were scanning were 145.24, 440.600, and 147.360 - the official event frequencies. We were also monitoring Close Call frequencies - namely, those from our Baofeng rally radios / helmet coms.

The scanner is hard-wired into the dash, with a Garmin GPS antenna attached, and a multi-band police antenna. [I forget the specific model but can look it up if it's helpful.] A Zoom H4N audio recorder was plugged into the "REC" port and was recording everything.

I can't imagine what might cause this.

Any ideas?

 

[TampaTyron]

Is the charger an OEM Apple product or an inexpensive clone? DC to DC converters used in vehicles are known to be noisy in the RF spectrum. I have seen several bulletins from federal agencies about using them along with radios in same vehicle. It is much worse at VHF than UHF/700/800...... TT

 

[vagrant]

I was in the mountains (middle of nowhere) when I first experienced the following a few years ago. Basically, RF interference is very low at that location.

I had various radios on (scanners, VHF/UHF, and HF) and I needed to charge/power some device via USB. I plugged in a 12v power plug to USB the noise floor immediately rose. A few plug and unplug motions confirmed this followed by my cursing.

I dramatically reduced the noise by fitting the device to be charged and the battery inside a folding Sterno stove and moving it away about 10 meters. Basically, if I wrapped the charger, device and cord in aluminum foil I would eliminate or at least dramatically reduce the unwanted RF noise on my radios.

What you experienced is RF interference from the 12v USB charger.
1. Make sure your phone is charged ahead of time
- or -
2. Charge your phone away from the radios and inside a metal box, or foil lined box/bag in the back seat.

I have tried several different 12v to USB converters/chargers and they all give off RF noise. Wrapping up the cord around various ferrite beads/rings did not help enough.

Start wrapping things using aluminum foil one at a time to see what may be enough.

 

[slicerwizard]

VHF/UHF hash from the SMPS. Not that unusual...

 

[UPMan]

To clarify, it isn't the phone that needs to be isolated from the receiver. It is the USB adapter (i.e. don't put the phone in a foil box/bag, put the adapter in there.

The RF gets in one or both of two ways:

1) Direct radiation into the antenna (not likely if antenna is mag mount outside the car);
2) Conducted through the power cable (most likely).

 

[N4KVE]

My wife was given a liter plug/USB adapter by her daughter. Suddenly she is receiving a loud alternator whine on her factory car stereo while using it. I immediately plugged the original adapter back into the liter, & the noise was gone. Threw the “gift” in the trash. Cheap JUNK.

 

[krokus]

Add me to the "try a different one" group. I have had some similar devices affect VHF scanning, and even blanket weaker FM broadcast stations. (Unless you want to spend time trying to shield the offending device, which could be frustrating.)

Sent using Tapatalk

 

[DJ11DLN]

The car charger for a flip phone I used to have did the same thing, this was before they all mostly used the micro-USB plug, it had a proprietary plug for the Samsung phone. Immense RFI if it was plugged in a vehicle. Got a data-transfer cord from the Verizon store that ended in standard USB-A and a cheap lighter plug, no more noise...and it even charged the phone about 50% faster than the "real" one. I found it kind of odd at the time that the "official" charger that cost about $25 was so noisy as to be unusable but a solution that came in under $7 caused zero problems. The Samsung-branded car charger even fuzzed up the broadcast radio, you could hear it even tuned to very strong stations.