Woof! You're now into uncharted territory. A few years back I needed HF DF
capability for a different reason. Got a lot of input on this topic, and
found out there is nothing available to us that will really do the job,
short of laying out lots of wampum.

I thought such eqpt might be scarce. But, I figured there was SOMETHING
around that would work. Turns out no one could put me onto anything,
without encountering exhorbitant cost. And,
some pretty knowledgeable and intelligent people answered up and explained
why there isn't anything available, without spending big bucks.

You know those old WWII movies where you see German vans with DF eqpt
driving around trying to locate spies? Turns out they were HF units. But,
it took three of them, in widely separated locations acting in unison to get
the job done. And, the triangulation wasn't precise. It took lots of time
and effort to narrow in on the general location of a spy sending.

Anyway, if you do find a way, please let me know. I no longer need the
capability, but am still curious if it can be done, and how.

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

Thanks for everyone's input. After two months of this interference, it has
just moved and is no longer a problem for the channels I need to use. So,
although it is still present, I no longer need to locate its source.

Peter


"Dave VanHorn" wrote in message
...

You know those old WWII movies where you see German vans with DF eqpt
driving around trying to locate spies? Turns out they were HF units.
But,
it took three of them, in widely separated locations acting in unison to
get
the job done. And, the triangulation wasn't precise. It took lots of
time
and effort to narrow in on the general location of a spy sending.

combine an hf loop, with aprs, and you'll be amazed how effective it is.
aprs will allow your hounds to share their info easily.
you get the location of the other stations, on a map, plus your own, and
all
the bearing data.

On Mon, 15 Sep 2003 12:49:16 -0400, "Peter Gottlieb"
wrote:

Thanks for everyone's input. After two months of this interference, it has
just moved and is no longer a problem for the channels I need to use. So,
although it is still present, I no longer need to locate its source.

Peter


"Dave VanHorn" wrote in message
...

You know those old WWII movies where you see German vans with DF eqpt
driving around trying to locate spies? Turns out they were HF units.
But,
it took three of them, in widely separated locations acting in unison to


It normally only takes two, but three does make it a bit more
accurate. Remember to use the null, rather than peak and if the
offender stays on for long you can do a creditable job of finding them
in 15 to 20 minutes.

We had a big field intensity rig (Singer) at work to measure field
strength and check for RFI (leaks). When you spend a lot of time with
those things you get to the point where you can take readings in a
hurry. Two units within a couple miles of a station should find it
in about 5 minutes if using APRS.

Roger Halstead (K8RI EN73 & ARRL Life Member)
www.rogerhalstead.com
N833R World's oldest Debonair? (S# CD-2)

get
the job done. And, the triangulation wasn't precise. It took lots of
time
and effort to narrow in on the general location of a spy sending.

combine an hf loop, with aprs, and you'll be amazed how effective it is.
aprs will allow your hounds to share their info easily.
you get the location of the other stations, on a map, plus your own, and
all
the bearing data.