vehicle noise
 

The noise you're picking up is obviously radiated and being picked up by
your antenna and not coming thru the power lead, as you have
demonstrated by using a separate battery. If you're using the wind-up
antenna, it's picking up every single ounce of stray radiated rf energy
from all the noise sources in the vehicle. You don't want the antenna
to receive anything until it gets outside of the vehicle, so you need
shielded coax from the radio to the antenna on the outside. But given
the confines of space, you obviously can't throw out 100' of wire, so
you're limited to some sort of vertical whip antenna...a 108" steel whip
is about as long as you can practically get - but that's still pretty
short for a shortwave antenna. So the way antenna manufacturers get
around that is to add a loading coil to make the radio "think" the
antenna is longer than it actually is...kinda'/sorta' what a hamstick
is. BUT - - you get them on a frequency other than where they're
designed and they suck! So to cover the shortwave spectrum, you'ld have
to get a BUNCH of hamsticks. I'd opt for a 108" steel whip plus a small
antenna tuner at the end of the coax by the radio.

Now, back to the noise problem...

I just picked up an MFJ-1026 "Noise Canceller" that I've experimented
with in the shack for both my ham rig as well as general coverage
receiver. I bought it as somewhat of a "crapshoot" figuring that I'd
throw something new at the noise and if it worked...fine; if not...it
was worth a shot. Few things you gotta' know about this noise
canceller...it's not like a noise blanker or DSP. The receiving antenna
and a 2nd antenna (to pick up the noise) are each plugged into this
unit, then a cable goes from it to your receiver. The way it works is
to "mix" the signals from the 2 antennas after it changes the electrical
phase of the signal from the noise antenna so it is knocked way down.
So it does require another antenna (can simply be a piece of wire) and
also quite a bit of a learning curve - - you tune this thing - carefully
- you don't simply switch it on and off. But it DOES work (at least, in
the shack). My next step will be to try it with my hf mobile rig (the
infamous Ford Explorer) - I *think* it should work but just haven't
tried yet. If so, it should make a dramatic improvement. More, later...

/Carl - W5SU
Dallas TX