Cellphones in the Audi

[tkomljan@mobility.com (Komljanec, Tony)]

Thanks to everyone on the cellphone harness post!  The group co-operative 
spirit in this list is great.

Anthony K.B. Chan wrote:
>some cellphones create
>interference to the radio in your car. My current cellphone, a portable
>Nokia 2160 TDMA digital phone generates some serious interference to the
>the radio when it receives a call

You must be quite the cellular user to have a 2160... latest Nokia TDMA... I 
have one too, until CDMA is available.  The buzzing you are hearing is the 
phone transmitter turning on and off.  It only transmits during it's 
assigned "slot", leaving two other slots available for others to use. 
 Analog transmitters turn on and stay on, so if you listened VERY carefully, 
you would only hear a click when it first keys up or when the phone 
registers, etc.

I installed the 2160 with in car kit + pro-fit custom bracket next to the 
passenger side seat heater control.  There are two screws there that the 
pro-fit bracket uses.  The in-car kit routes RF to the external glass mount 
antenna.  The RF is thus well away from any audio circuits.  If I operate 
the phone in my hand, next to the radio,  the buzzing is heard.... this is 
normal... called audio rectification.... similar to hearing CB (AM) coming 
thru your home/car stereo or wire-line phone....  instead of amplitude 
modulation, ie voice, you hear the transmitter key/unkey transients 
superimposed on your audio.  With the phone in the cradle and RF routed 
away.... no radio buzzing.

I also operate 50W VHF/UHF transmitters in the car without difficulty... 
again, audio is routed via optical fiber to the trunk, where the transmitter 
is located.  RF is kept well away from computer, ABS and audio circuits. 
 The antenna is an NMO "L" bracket mount on the rear passenger trunk lip. 
 The antenna is a black cellular look-alike, so the car simply looks like it 
has two cellulars.

Regards,

Tony K

Toronto, ON
93 100 CSQ