Re: [amsat-bb] Re: Inquiry

[Franklin Antonio <antonio@xxxxxxxxxxxx>]

At 02:26 PM 4/26/99 , GPersons wrote:
>"NO GROUNDING IN PASSENGER COMPARTMENT."
>Can anybody suggest why they would want to not ground in the passenger
>compartment? On a vehicle, it would seem to me that a ground is a ground.

Well I suspect that they fear high currents (RF or DC) which would produce 
voltage drops, and make other systems malfunction.  I don't think it's 
correct to think that "a ground is a ground".  In particular, the various 
pieces of the passenger compartment (especially around the dash) in a 
modern car may be connected together in a complex way, involving plastic 
parts, things that look like wood screws etc.  Some pieces look like metal, 
but are really plated plastic.  Sometimes there aren't even any 
screws.  Sometimes the pieces snap together.  It ain't the construction of 
your daddy's car.  A high R in the ground path turns into a voltage drop 
when current flows thru.

In addition, there's usually an engine control computer under the dash 
somewhere.  These things often have analog inputs which could easily be 
disrupted by some voltage drops in the ground system.  It ain't the engine 
control system of your daddy's car either.

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