[Top] [All Lists]

[RFI] An odd source of automotive RFI

To: <rfi@contesting.com>
Subject: [RFI] An odd source of automotive RFI
From: k2kir@telenet.net (Bud Hippisley)
Date: Wed, 27 Feb 2002 11:01:36 -0500
The DC charger included in the Nokia "hands free" kit sold in a blister pack by 
Cingular in its stores in this area (New York State now *requires* hands free 
operation) is especially obnoxious in its emanations across the AM broadcast 
band.  The on-off rep rates of the offending interference (which sounds like a 
squeal or "yowl" on the AM band) are even slower than those that Pete observed 
from his adapter.  This new Cingular adapter appears to have a printed circuit 
card with surface mount devices on it; if I can figure out how to fully open 
the case without breaking anything I'm going to see if I can clean it up.  

I have powered earlier Erickson and Nokia handhelds with a variety of DC 
adapters.  At one time the DC charger sold by Cingular for the Erickson phones 
was perfectly clean, but a third party charger I purchased for the same cell 
phone put substantial broad band (but constant amplitude) hash in the car 
radio, both AM and FM.

Bud, K2KIR    

At 02:35 PM 2002-02-25 , Pete Smith wrote:
>my truck seemed to have
>something in it that was often emitting a very loud, short chirp of RF
>every .7 seconds or so.  
>Today, I accidentally found the answer.  I have one of Nokia's ubiquitous
>analog cellular phones (a model 908?) plugged into my cigarette lighter
>jack. It appears that there's something in the
>charging circuit of the phone that causes this noise, regardless of whether
>the phone is on or off, so long as it is plugged in.  Disconnect the phone
>from the car cord, or the car cord from the lighter jack, and it goes away.

<Prev in Thread] Current Thread [Next in Thread>