Re: Automobile Cell Phone Charger RFI


On 08/30/2018 03:21 PM, Rick Ellison wrote:

I have a 4 port charger that makes listening to FM barely hearable and totally wipes out AM. I had never thought of using SDRC to track it down.


73 Rick N2AMG

I am sort of surprised that your device contains a switcher when all you need is 5 Volts DC from a 12 to 15 volt cigarette lighter socket. I would put a 5V series regulator in the charging device and it
would make no RFI at all. Perhaps there is one made like that. I have a two-port lighter plug with USB jacks on it. I will take a look and see if it generates RFI. And my phone came with a separate
charging cord compatible with a USB jack, which the AC charger has on it. (And IT is a switcher of course, sind it plugs into the houshold AC.)
In the meantime, Does the device you have have a built-in charging cord that goes to the phone, or do you use a separate USB to phone cable? If it's a separate cable, then disconnect it and see
if the RFI goes away sufficiently to listen to the radio. If it does, then get some ferrite snap-on RF chokes and run the charging cord thru about three of them right next to the lighter socket. And you
can wind a coupe of turns of the cord thru each choke.
If that doesn't work, you will have to find a charger made with that series regulator. They are almost certain to exist.

--doug, WA2SAY, retired RF engineer.


Am 29.08.2018 um 22:08 schrieb Kriss Kliegle:

Noticed a charger I picked up from one of my favorite electronic surplus sites made listening to FM difficult while charging the phone.
Did some tests on 99.5Mhz with the SDRplay and a 27" (68.6cm) whip located nearby.

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