From: everett@nmerh97.NoSubdomain.NoDomain (Jerry F. Everett)
Newsgroups: rec.radio.amateur.misc
Subject: Re: RFI susceptability of new cars?
Date: 7 Jan 93 19:58:52 GMT
Organization: Bell Northern Research

My RFI susceptability is so bad I took the rig out of my GM car....Read on!!

In article <1993Jan03.232623.4498@uhura.neoucom.edu>, wtm@uhura.neoucom.edu (Bill Mayhew) writes:
|> Automobile manufactures subject their cars and trucks to rather
|> extensive EMI/EMC testing.  Over the last several years GM
|> engineers have had a display at the Dayton Hamvention on proper
|> installation of mobile radio transmitters.  Due to the dangers of
|> litigation in the face of eqipment failure to RFI, auto
|> manufactures have to conduct extensive testing for suspectibility
|> from on-board and external RFI.  An RF anechoic chamber large
|> enough to hold a Semi truck tractor is pretty impressive.
|> 

I really have got to get to Dayton one of these years....

|> I've had several cars with microprocessor engine contols, and have
|> not yet experienced troubles with up to 50 watts on 2m, 70cm or 3
|> watts from my cellular phone.  The AM/FM receivers have had some
|> intermod problems, however.  Occasionally, the FM radio in my Mazda
|> MX6 gets hammered by police radar units when I pass near a cruiser.
|> I get a loud buzz in the speaker as I go by.
|>

My problems with vechile RFI have been a bit different. 

First a overview of my system:
Chev Cavalier 1990 (There is noooo waayyyy I am going to drill a hole and believe me
                    when I tell you I am a truely fanatic ham. It is my first car.)

Radio: Kenwood TM-241A 2 Meter rig. Problems only on 50 watts. Same power as Bill.
Antenna: Antenna Specialist, ON GLASS mount, for 2 meters.
Config:  DC is taken from the fuse panel. (I know it should be on the battery
                                             but it is really tough to attach the leads
                                             to the battery Terminals)
         Coax runs from under the AM/FM radio, through the enclosed  moulding which runs
         up the side of the windshield to the roof, back along the roof (under the
         roof fabric) to the middle of the back windshield. The antenna is mounted
         as close to the metal of the roof as possible.
         The SWE is around 1.5:1 last time I checked.

PROBLEM:  When I use 50 watts:
          - The dome light comes on.
          - The AM/FM radio generates a load hum. (RF getting in somewhere)
          -  My "shift up" light comes on.
          - On occasion there is a clicking/light_thunking sound from the doors. (Sounds
            similar to when you press the power door lock button when the doors have
            already been locked.)
          

I have tried small chokes at both the antenna and radio ends of the coax. The antenna has
been installed as per instructions, including the little wire strap to the metal of the roof.
No problems with the low and mid power levels. 

Thought someone might like to know.


...Jerry VE3XPM

=======================================================================
Jerry Everett
Technical Assistance Engineer. Product Support.
Northern Telecom Canada Ltd., 1285 Baseline Road
P.O. Box 3511, Stn. C, Ottawa, Ontario, K1Y 4H7
PHONE: 613-763-9696    FAX:     613-765-4060
INTERNET: JEVERETT @ BNR.CA     AMPR: VE3XPM @ VE3JF.#EON.ON.CAN.NOAM
>> All material herein is my own and does not represent the views    <<
>> or opinions of Bell Northern Research or Northern Telecom.        <<
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