I have an interesting delima in my mobile HF installation.
Vehicle: 2002 Toyota Highlander
Radio: Icom 706 MKIIg
Ant: High Sierra screwdriver.
I'm experiencing a noise that is very evident in AM on 10 - 20 meters
(almost S9) but even though I can't hear it, suspect it's causing some
desensing on SSB or CW as well. The noise is present only when the
engine is running, is constant in frequency, and sounds almost like two,
one about 600 Hz and the other an octave lower. It's not the fuel pump,
(ignition on it's quiet until the engine is running... a fuel pump, in
my experience would run for a short period when the ignition is first
turned on and if that were the case, I'd hear the noise then, but I
don't) or any fans, (as near as I can tell, they are all turned off) and
I'm certain it's not the alternator because it doesn't change
frequency. I used a piece of coax with a loop on the end to try to
sniff out the noise and... are you ready for this... it appears to be
originating from under the drivers seat. I put several snap-on ferrite
cores (similar to what is on a computer power cord) on the coax as it
leaves the antenna and that reduced the noise somewhat so I'm suspecting
it's coming in on the shield as well a being picked up by the antenna.
I haven't looked at the noise with an o'scope nor have I connected the
control head directly to the radio, sans cable, but that's my next step.
Is anyone running HF in a Highlander and or experienced something
similar to what I'm hearing?
BTW... I was having RF shut-down as experienced by Scott, KA9FOX and
solved that with a good ground at the radio and a ferrite core on the
separation cable for the control head.
Tnx es 73
Dick
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Dick Bodine, N0IM
Duluth Minnesota
mailto:rbodine@cpinternet.com
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