Caprice 9c1 Police

[copcarcrzy]

I am in the process of restoring my 1996 caprice 9c1, while replacing the trunk carpet I notcied a bolt to the drivers side, checking under the car there is a ground going from the trunk to the bumper bracket then to the frame..

anyone have an old 9c1 with the same thing, and anyone know why this was done this way, or is this just the old department rigging something to work ???

[radioman2002]

Most Police cars have additional grounding straps throughout the car to keep the engine noise out of the 2-way radios. My old Chryslers had a strap from every body part to every other body part.

[HLandin]

I also have a grounding strap from the body to the trunk. What radioman2002 posted seems to make sense; I can't think of any other explaination for the grounding.

[silicon212]

The grounding is there to ensure the entire body has electrical continuity. Radio transmitters require an antenna which has a counterbalance (ground plane) in order to operate at max efficiency and keep from being damaged. The antenna you see on the trunk is half the equation - the car itself forms the counterbalance and any electrical grounding issues on a car can inhibit the transmitted signal, with some of it being "reflected" back into the transmitter. Any reflected power is power wasted and range reduced. Enough reflected power and the transmitter becomes toast.

Hence, grounding straps.

[radioman2002]

Well it seems there is someone else out in PD land that understands antenna theory. LOL. To be more precise, the transmitter antenna is a 1/4 wave, as most are advertised. The other 1/4 is the car, usually only the trunk deck or roof (the best spot) not necessaraly the rest of the car. (If you look at most of the PD car brouchures they list the bonding as radio interference suppression) Transmitters are tuned for a 1/2 wave of their frequency for best performance, that is why even a new antenna must be tuned to the correct frequency (resonace) for the particular vehicle. I have found that even some cars of the same type, will need differenet lengths of the whip.

[silicon212]

All good, except police transmitter antennas are 5/8 wave base-loaded in the case of 160MHz radios, or 5/8 wave single length for 800MHz radios.