On 9/16/2020 11:13 AM, David Gottschalk wrote:
I'm looking for some help and guidance in next steps I can do to
resolve a mobile noise issue I have.
I own a 2006 Sequoia that I bought new in Nov 2005. With the help of a
local ham who opened his business's enclosed loading dock in a Chicago
winter to give us a place to work on it, we pulled power from the
battery through the firewall, and installed a mount for Ham Sticks on
one of the mounts for the luggage rack. Before selecting the spot, we
probed around a lot with an Ohmmeter, looking for connections to the
body and frame. Lots of points that looked good physically proved to be
insulated from the body by paint -- even two bolts very close to each
other had no conductivity at all between them!
Eventually we did find a suitable point to bond the coax shield, and the
HF radio seemed to work, although I noticed that the fan that was part
of the passenger compartment heating system speeded up as I transmitted
on 17M.
A few weeks later, I headed west to Northern California, where we had
bought a home, and I worked some 17M on the road. The next day, driving
through the high desert in northern NV, I called CQ on 20M SSB, got two
replies, but also noticed I had slowed down to 15 MPH -- RFI to the
car's wiring had put the computer running it into "limp-home" mode. Had
to pull a battery lead to reboot it!
I don't remember a lot of RF noise in the radio, but that was 15 years
ago, and now that I've completed the move, I have little interest in HF
mobile, so I haven't bothered fixing the problem. :)
In addition to the advice you've received about bonding the tailpipe, I
suggest running twisted pair for power direct to the battery (using
frame ground where the battery V- is bonded for V-), NOT letting the
radio chassis contact any part of the vehicle, doing your best to
provide the largest possible "hunk" of electrically continuous
body+frame to act as a counterpoise for the TX antenna, and bonding coax
shield to it.
73, Jim K9YC
73,
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