On Sun, 14 Sep 2003 05:18:50 GMT, "Peter Gottlieb"
wrote:

Not sure this is the right ng for this.

I am trying to track down a very strange interference signal. This signal
has a carrier which sweeps from about 4410 to 4470 KHz at about 1 sweep per
second and seems to have what appears (from FFT) to look like a 512 Hz
modulation (further modulated by other frequencies).

I made a tuned 2 foot diameter loop antenna and drove around plotting the
null headings. All pointed to a place somewhere in central New Jersey. So
I drove over there to make more readings. As I got closer I had to
attenuate the antenna signal, but when I got right to the area, there were
no more antenna nulls.

So. Here are my questions:

1) Do I need a better antenna for this?

2) Is the source spread out, like coming from power lines, and not
something I can find using that method?

3) Has anyone ever heard interference like this? (I haven't in over 35
years of SWLing and hamming).

TIA,
Peter


A DF loop, with null seeking arrangements, only provides a line of
bearing to the transmitter. Triangulation is required to localize the
signal, subject to the limitations of multipath in an urban
environment.

If you can triangulate the source of interference to within a defined
area (by taking multiple readings at various locations to help average
out some of the effects of multipath) this would serve as a good
starting point for your search.

Within the search area, you're probably better off trying to use a
receiver with a signal strength indicator, or a field strength
indicator, to look for "hot spots" as you drive around. As you get
closer to the source, keep attenuating the signal and repeat the
search process. With this process, you may be able to localize the
source to within a building or group of buildings.

Mark

Never had to do this but if it ever came about
I would put a radiation pattern program on a lap top
and connect it to a small directive antenna on the
automobile.Circle the area in question and do a
rotation of the antenna starting of at north
each time. Do this for a close in radius ( a mile)
and then for a larger radius, An overlay of all
patterns shgould be able to triangulate it
pretty close.
See antenna commpedium article ( book #1,2 or 3)
by Peter Dodds of the U.K.

Art



Mark wrote in message . ..
On Sun, 14 Sep 2003 05:18:50 GMT, "Peter Gottlieb"
wrote:

Not sure this is the right ng for this.

I am trying to track down a very strange interference signal. This signal
has a carrier which sweeps from about 4410 to 4470 KHz at about 1 sweep per
second and seems to have what appears (from FFT) to look like a 512 Hz
modulation (further modulated by other frequencies).

I made a tuned 2 foot diameter loop antenna and drove around plotting the
null headings. All pointed to a place somewhere in central New Jersey. So
I drove over there to make more readings. As I got closer I had to
attenuate the antenna signal, but when I got right to the area, there were
no more antenna nulls.

So. Here are my questions:

1) Do I need a better antenna for this?

2) Is the source spread out, like coming from power lines, and not
something I can find using that method?

3) Has anyone ever heard interference like this? (I haven't in over 35
years of SWLing and hamming).

TIA,
Peter


A DF loop, with null seeking arrangements, only provides a line of
bearing to the transmitter. Triangulation is required to localize the
signal, subject to the limitations of multipath in an urban
environment.

If you can triangulate the source of interference to within a defined
area (by taking multiple readings at various locations to help average
out some of the effects of multipath) this would serve as a good
starting point for your search.

Within the search area, you're probably better off trying to use a
receiver with a signal strength indicator, or a field strength
indicator, to look for "hot spots" as you drive around. As you get
closer to the source, keep attenuating the signal and repeat the
search process. With this process, you may be able to localize the
source to within a building or group of buildings.

Mark