On Mon, 11 Jan 2010 15:39:32 -0500, David Jordan wrote:
>I have attached a link to the Ford Mobile Radio Installation Guidelines:
>http://www.fordemc.com/docs/download/Mobile_Radio_Guide.pdf that should help
>you with your mobile installation and ignition noise reduction. The RFI
>Suppression Beads may help with your ignition noise. Often it is the fuel
>injectors that cause the ticking interference and beads have helped in some
>cases. Also, the coil or spark unit maybe treated with beads. Each case is
>different, so you will need to do some experimenting on mobile noise
>suppression. Bonding the engine and the hood to the frame with tinned copper
>braids may also help.
This is pretty good advice, especially the recommendation for bonding between
pieces of the body that appear to be connected but often are not. Hood hinges
are a point where bonding is needed because the hinges have little or no
electrical conductivity! Bonding the hood to the body would thus improve the
shielding provided by the hood (although the long slots along the side of the
hood contribute a large break in the shielding, which lets out a lot of RF.
Note that the Ford piece is generic and more than ten years old. While the
physics of radio doesn't change, a LOT more electronic systems are built into
cars today than in 1998. That means more trash and more susceptibility.
FWIW -- one of my good friends in the broadcast engineering world is Warren
Schulz, chief engineer at WLS (50kW on 890). At about the time Ford's RFI
document was written, Warren was telling me that the noise in Ford vehicles
was so bad that the radios in Ford vehicles couldn't hear his non-directional
50kW clear channel station ten miles away.
Jim Brown K9YC
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