[RFI] Mobile Noise in Toyota(s)

[Jim Brown]

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,