On Mon, 19 Jan 2009 17:14:27 -0800, Jeff Liebermann
wrote:

Daytime coverage map:
http://www.radio-locator.com/cgi-bin/pat?call=KGO&service=AM&status=L&hours=D
2.5, 0.5 and 0.15 mV/m contours. It still should be usable in
Sacramento. Something is wrong.

Mo
http://www.fcc.gov/fcc-bin/amq?list=0&facid=34471
http://www.fcc.gov/ftp/Bureaus/MB/Databases/AM_DA_patterns/249372-2649.pdf
The antenna pattern is pretty much dead to the east and north-east.

--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831-336-2558
# http://802.11junk.com
# http://www.LearnByDestroying.com AE6KS

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 in message
...


snip

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.

I needed to abandon my van's fender-mount antenna because the shield ground
broke and AM reception was pretty awful, with spark plug noise and assorted
clicks and pops whenever I wasn't parked.

I got a connector adapter which plugged into the antenna jack on the back of
the radio. I connected a VHF magnetic mount ham radio antenna to it. I now
have a cable running between the bucket seats and out the back door but I
have really good AM/FM reception. On long trips, like across the southern
deserts, I unscrew the standard element and replace it with a longer element
(about 4') and AM reception is improved dramatically. The cable from the
fender-mount antenna dangles inside the dashboard, unseen and unused.

If you think you might tackle such a project, post again and I'll provide
more details. Having a limited knowledge of electronics is not a problem;
finding just the right parts is.

"Sal"

On Jan 19, 7:14*pm, Jeff Liebermann wrote:
Daytime coverage map:
http://www.radio-locator.com/cgi-bin/pat?call=KGO&service=AM&status=L...
2.5, 0.5 and 0.15 mV/m contours. *It still should be usable in
Sacramento. *Something is wrong.

Agree. The link below leads to an example of the noise on a weak,
daytime AM signal received from WBBM, Chicago (50 kW non-D on 780 kHz)
on a Sony ICF-2002 with its internal antenna, indoors in an urban
location. The groundwave path from WBBM to the receiver is about 225
miles in length. According to the FCC propagation curves, WBBM has a
daytime groundwave field intensity of about 0.14 mV/m for this path
(probably less in an urban area).

The noise in this MP3 clip maybe is tolerable for short-term
listening, or if there is nothing better receivable.

The recording was made Jan 10, 2009 at about 12:30 pm CST.

http://www.datafilehost.com/download-18b37f18.html

RF

Richard Fry wrote:
On Jan 19, 7:14 pm, Jeff Liebermann wrote:
Daytime coverage map:
http://www.radio-locator.com/cgi-bin/pat?call=KGO&service=AM&status=L...
2.5, 0.5 and 0.15 mV/m contours. It still should be usable in
Sacramento. Something is wrong.

Agree. The link below leads to an example of the noise on a weak,
daytime AM signal received from WBBM, Chicago (50 kW non-D on 780 kHz)
on a Sony ICF-2002 with its internal antenna, indoors in an urban
location. The groundwave path from WBBM to the receiver is about 225
miles in length. According to the FCC propagation curves, WBBM has a
daytime groundwave field intensity of about 0.14 mV/m for this path
(probably less in an urban area).



In this situation a Select-A-Tenna will work wonders. No good for a car
radio, however.

http://www.old-fashioned-values.com/...ct-a-tenna.htm

On Jan 20, 7:58*am, Dave wrote:
Richard Fry wrote:
On Jan 19, 7:14 pm, Jeff Liebermann wrote:
Daytime coverage map:
http://www.radio-locator.com/cgi-bin/pat?call=KGO&service=AM&status=L...
2.5, 0.5 and 0.15 mV/m contours. *It still should be usable in
Sacramento. *Something is wrong.

Agree. *The link below leads to an example of the noise on a weak,
daytime AM signal received from WBBM, Chicago (50 kW non-D on 780 kHz)
on a Sony ICF-2002 with its internal antenna, indoors in an urban
location. *The groundwave path from WBBM to the receiver is about 225
miles in length. *According to the FCC propagation curves, WBBM has a
daytime groundwave field intensity of about 0.14 mV/m for this path
(probably less in an urban area).

In this situation a Select-A-Tenna will work wonders. *No good for a car
radio, however.

http://www.old-fashioned-values.com/...enna_improve-a...

On a lot of AM auto radios the SN ratio really stinks and an external
preamp especially one with some preselection can really help. As
previously stated on radios with adequate sigal to noise ratio adding
a preamp just makes things worse.


Jimmie

I got a connector adapter which plugged into the antenna jack on the back
of
the radio. I connected a VHF magnetic mount ham radio antenna to it. I
now
have a cable running between the bucket seats and out the back door but I
have really good AM/FM reception. On long trips, like across the southern
deserts, I unscrew the standard element and replace it with a longer
element
(about 4') and AM reception is improved dramatically. The cable from the
fender-mount antenna dangles inside the dashboard, unseen and unused.


I have done the same thing with a spare 2 meter 5/8 whip (without the base
matching coil) on the roof with excellent results. The length is little
longer than stock. I used to own an older European car that had a 3 section
whip that was nearly 5' long fully extended and I wish I could find another.
A 102" CB whip will do better on AM (although less optimal for FM). There
used to be CB/AM/FM splitters for truckers, but I don't know how well they
work. The stock whip is far short considering the wavelength, so the
longest you can get on the car will only improve the capture area. As
mentioned, you will notice a peak if you adjust the trimmer in the radio to
your new antenna. They are usually peaked for 1300 kc anyway, so that might
be something to toy with first if you don't mind sacrificing the high end of
the band. An HF antenna with tuner would be the best you could do. In the
campsite, you can clip a longwire on and throw it in the trees.

On Jan 20, 11:29*am, JIMMIE wrote:


On a lot of AM auto radios the SN ratio really stinks and an external
preamp especially one with some preselection can really help. As
previously stated on radios with adequate sigal to noise ratio adding
a preamp just makes things worse.

Jimmie

I wouldn't say that. Most all the auto AM radios I've had were
quite good. Always plenty of sensitivity as long as the antenna
was functioning correctly.
The current car I'm driving "Corolla" uses a small helically wound
antenna, which is at the rear of the roof. It's pretty short overall,
and I still have plenty of sensitivity. The daytime is the best time
to check that, and I've never had any trouble receiving out of
town stations. And if I tune to an open frequency, I hear background
atmospheric noise, so any increase in sensitivity is pretty much
useless. I've had older Delco radios in cars and the AM was
excellent on those.
If the OP can hear background noise when tuned to an empty
frequency, and not have it sound "dead", adding more pre-amp
is unlikely to help.
I think the main culprit in this case is propagation, and the
pattern of the array, and unfortunately, I think he's basically
out of luck. Normally you would probably be able to hear the
ground wave out to at least 200-300 miles in the daytime,
but that assumes a fairly stout signal. If the pattern is away
from that direction, even the ground wave possibilities start
to look kind of bleak.
If an auto AM radio does not have enough sensitivity, it usually
means there is something wrong with it, or the antenna.
Most as they come from the factory have more than enough.

wrote:
On Jan 20, 11:29 am, JIMMIE wrote:


The current car I'm driving "Corolla" uses a small helically wound
antenna, which is at the rear of the roof. It's pretty short overall,
and I still have plenty of sensitivity.

Newer cars have active antennas.

Dave wrote:
wrote:
On Jan 20, 11:29 am, JIMMIE wrote:


The current car I'm driving "Corolla" uses a small helically wound
antenna, which is at the rear of the roof. It's pretty short overall,
and I still have plenty of sensitivity.

Newer cars have active antennas.

The helical on some antennas is for wind noise.