wrote in message
...
Hi all,

I've looked on the web, but with very little success. I have never
posted to this group before, so I apologize if my question is lame.

I listen to the Bay Area's KGO 810 MHz a lot. Their transmitter is
located in South San Fran Bay near the Dumbarton Bridge, and outpus 50
kW (that's what they say anyway). I am guessing, it's directed mostly
at the Pacific coast line. I often listen while driving east on I-80
to Truckee/Tahoe for skiing and camping. Usually the signal fades
substantially by the time I reach Sacramento - but it's still
tolerable listening (by ear, S/N of ~3). By the time I reach Auburn
it's essentially inaudible. Much better signal at night (~again, by
ear, S/N improves by ~2). At night, I can sort of pick up words in
truckee.

Question: can I *substantially* improve the S/N - say, factor of
2/5/10 by installing a better car antenna, so that, say, I could
listen in the Sierras day and night? I do not care if the antenna is
huge/geeky_looking, my car is being driven into the ground anyway. I
would be happy to make this a DIY project - to save on $ and learn
about radio. What kind of specs should I look for? I.e. I don't want
to go on the web and blindly buy an antenna advertised to "boost" your
AM radio reception - I would want some numbers.

I have limited knowledge in electronics, my background mostly is in
biophysics and biochemistry. So if you steer me into the right
direction I think I should be able figure it out.


Presumably you mean 810 kHz. What is the source of the noise? Noise
generated in the receiver is usually insignificant in the medium-wave band.
If the cause is other transmissions on the same and nearby frequencies you
may not gain much by changing the antenna, but a receiver with better
channel (IF) filtering may help if there is any contribution from adjacent
channels. If the noise is coming from your car (does it improve when you
park in a rural area) then you may need to improve the RF suppression of its
circuitry (e.g. ignition if it's a petrol engined car).

I expect you can work out what tests would be needed to locate the principal
sources of the noise.

Chris

Presumably you mean 810 kHz. *What is the source of the noise? Noise
generated in the receiver is usually insignificant in the medium-wave band.
If the cause is other transmissions on the same and nearby frequencies you
may not gain much by changing the antenna, but a receiver with better
channel (IF) filtering may help if there is any contribution from adjacent
channels. *If the noise is coming from your car (does it improve when you
park in a rural area) then you may need to improve the RF suppression of its
circuitry (e.g. ignition if it's a petrol engined car).

I expect you can work out what tests would be needed to locate the principal
sources of the noise.

Chris

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?

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

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?

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

wrote:

Is there anyway to "filter" the 810 frequency somehow?

The noise is also at 810 kHz.

Noise can sometimes be separated from a signal at the same frequency if
there's some distinguishing characteristic of the noise, like fast rise
time or a periodic nature, so it can be selectively removed. One device
that can do this for a few special noise types is a "noise blanker".
Modern audio signal processors (or "digital signal processors" - DSP)
are considerably more sophisticated and can remove a wider range of
noise types. But good ones aren't cheap, and probably not easily adapted
to your radio. And they do best when the incoming S/N ratio is
reasonable. You'll be encountering a pretty wide range of noise sources
as you drive along, so I doubt that any kind of processor would be very
successful at removing all, or even a substantial portion, of them.

Roy Lewallen, W7EL

wrote:
Presumably you mean 810 kHz. What is the source of the noise? Noise
generated in the receiver is usually insignificant in the medium-wave band.
If the cause is other transmissions on the same and nearby frequencies you
may not gain much by changing the antenna, but a receiver with better
channel (IF) filtering may help if there is any contribution from adjacent
channels. If the noise is coming from your car (does it improve when you
park in a rural area) then you may need to improve the RF suppression of its
circuitry (e.g. ignition if it's a petrol engined car).

I expect you can work out what tests would be needed to locate the principal
sources of the noise.

Chris

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?

Does it do this for KKOH as well? Try 780 and see if it exhibits
similar behavior. If not, it's the KGO signal. They are pretty anemic
to the East North East.

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