On Fri, 04 Feb 2005 10:30:31 -0800, digital-conjurers@adelphia.net
wrote:
>Will the radiated RF power at this HF frequency, in the config
>above, have the potential to fry any of the on-board computers
>or electronics in the vehicle?
Unlikely if you follow good engineering practice.
1) Get your power directly from the battery ( both positive and
negative).
2) Run coax with good copper braid to the antenna, bond the braid
to the car body at the antenna, AND -- VERY IMPORTANT -- MAKE SURE
THE CAR BODY AT THE ANTENNA IS BONDED TO THE REST OF THE CAR BODY.
This will also maximize the radiation efficiency of the antenna
and minimize the receive noise.
#2 is not trivial. I use a license plate mount to put a Ham Stick
on my Volvo S80. The license plate screws are insulated, so that
requires a copper bond between the mount and the trunk lid metal.
BUT -- the trunk lid isn't bonded to the car body, so that
requires ANOTHER copper bond between the trunk lid and the car
body (around the hinges).
3) K9IKZ has observed that it is also helpful to bond the tailpipe
to the car body at both ends to minimize receive noise. I would
also expect this to minimize RF getting into the computers. My
Volvo is fairly quiet (but not dead quiet), and I haven't gotten
around to doing this yet.
FWIW, I run 100 watts in my Volvo, which is also loaded with
microprocessors, and have never had a sign of RFI to the car. Of
course, it's a European car, and Europeans are generally more
sensitive to EMI, thanks to the EU's EMC directive.
Also FWIW, others have made a big point of bonding the radio to
the car body via its mount. My FT100D (yeah, I know, not a great
receiver) sits on the hump between me and the passenger seat. I'm
lazy about installs, and I mostly use in in the shack on our
club's FM repeater. If you've done #1 and #2 right, it doesn't
matter.
Jim Brown K9YC
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