wrote in message
...
On Jan 19, 3:38 pm, Roy Lewallen wrote:
wrote:

Yes, KHz, sorry.

The noise goes up several fold when I pass underneath bridges/pass big
trucks, etc. Does this suggest that the noise is from other
frequencies?

No. It means that the noise is coming from outside your car. Your
antenna and radio can't tell the difference between this noise and the
desired signal, so improving your antenna or increasing your receiver's
sensitivity will simply increase the signal and noise in the same
proportion. And because it's not coming from your own car, there's no
way for you to reduce the noise. In other words, there's really nothing
you can do to improve the S/N ratio in the presence of that noise.

Roy Lewallen, W7EL

increase the signal and noise in the same proportion.
Is there anyway to "filter" the 810 frequency somehow?

Hi

Are you certain that the noise increases? I suspect the "signal"
decreases. It is entirely possible that the antenna on your vehicle is
inadequate.
Car antennas are *not* simple. They do appear simple. They often appear
to be a whip mounted above the fender. The way that fender whip is
connected to the receiver is critical.

Depending what type vehicle you have, the increase of sensitivity to 810
KHz could be to mount a stub atop the fender and connecting it to the
receiver with a Low Capacity coax line. In addition, the receiver can be
tuned at the place where the antenna connects to the first amplifer to
maximize sensitivity to 810 KHz.

Many new cars include an amplifier at the base of the antenna to increase
sensitivity.

Are you open to taking your car to a specialist to let them try to tune
your "antenna" to your receiver?

Jerry KD6JDJ