In Scott in Aztlan
wrote:

Clearly you could use trilateration with any 3 of the data points and
get an estimate, ...

Since I'm not familiar with the term "trilateration", I'm guessing that
you mean "triangulation"?

But without a bearing to the transmitter from your location, how can you
do triangulation? That's why simple DF techniques use directional
antennas.

If you knew the output power of the transmitter, knew the radiation
pattern of the transmitter's antenna and knew the signal propagation
characteristics at the instant you took your signal strength reading, you
might be able to make a guess as to your current distance from the
transmitter, and draw a circle of that radius around your location.

Repeat this for enough points, look at all the places that all the circles
interesect and you might find your transmitter.

Other than being able to mark your location on a map and then navigating
to the possible transmitter location(s), I don't see a GPS receiver being
much direct use in this application.

--
Bert Hyman St. Paul, MN

In Scott in Aztlan
wrote:

Clearly you could use trilateration with any 3 of the data points and
get an estimate, ...

Since I'm not familiar with the term "trilateration", I'm guessing that
you mean "triangulation"?

But without a bearing to the transmitter from your location, how can you
do triangulation? That's why simple DF techniques use directional
antennas.

If you knew the output power of the transmitter, knew the radiation
pattern of the transmitter's antenna and knew the signal propagation
characteristics at the instant you took your signal strength reading, you
might be able to make a guess as to your current distance from the
transmitter, and draw a circle of that radius around your location.

Repeat this for enough points, look at all the places that all the circles
interesect and you might find your transmitter.

Other than being able to mark your location on a map and then navigating
to the possible transmitter location(s), I don't see a GPS receiver being
much direct use in this application.

--
Bert Hyman St. Paul, MN

Many people (including myself) use the word "triangulation" very loosely here
because it's a word most people can understand, but purists would not call what
GPS does "triangulation" because no angles are involved. But just so we don't
confuse new folks learning GPS, it's really "trilateration" or "resection".

Ref: http://www.trimble.com/gps/triangulation.html
http://www.Colorado.EDU/geography/gc...gps/gps_f.html

Trilateration
The measurement of distances... to fixed positions to determine an
originating location. The process is normally to control points on the
surface of the earth. In GPS trilateration, the fixed positions are
instead satellites orbiting the earth with distance determined by the
GPS signal travel time to a location on the surface of the earth. A
four satellite trilateration provides an accurate earth position.


Triangulation
The measurement of angels... to determining the location of an unknown
point, as in GPS navigation, by using the laws of plane trigonometry.

Many people (including myself) use the word "triangulation" very loosely here
because it's a word most people can understand, but purists would not call what
GPS does "triangulation" because no angles are involved. But just so we don't
confuse new folks learning GPS, it's really "trilateration" or "resection".

Ref: http://www.trimble.com/gps/triangulation.html
http://www.Colorado.EDU/geography/gc...gps/gps_f.html

Trilateration
The measurement of distances... to fixed positions to determine an
originating location. The process is normally to control points on the
surface of the earth. In GPS trilateration, the fixed positions are
instead satellites orbiting the earth with distance determined by the
GPS signal travel time to a location on the surface of the earth. A
four satellite trilateration provides an accurate earth position.


Triangulation
The measurement of angels... to determining the location of an unknown
point, as in GPS navigation, by using the laws of plane trigonometry.

Your scheme is doomed to failure.

Although signal strength is proportional to disrtance it
is also affected to too many other things as well.

For your scheme to work both transmit and receive
antennas must be truly omni-directional with no
lumps in the polar diagram (not easy espicially
mobile). The terain must not cause any disturbance
to the signal (impossible). There should be no
reflections. The transmit power or receive gain
must not change. I am sure there are a few more
that I have not thought of off the top of my head.

Having said that such a scheme could give a very
approximate location if the data was analysed and
anomolous readings ignored.

Regards
Jeff

Your scheme is doomed to failure.

Although signal strength is proportional to disrtance it
is also affected to too many other things as well.

For your scheme to work both transmit and receive
antennas must be truly omni-directional with no
lumps in the polar diagram (not easy espicially
mobile). The terain must not cause any disturbance
to the signal (impossible). There should be no
reflections. The transmit power or receive gain
must not change. I am sure there are a few more
that I have not thought of off the top of my head.

Having said that such a scheme could give a very
approximate location if the data was analysed and
anomolous readings ignored.

Regards
Jeff

"Jerry L. Wahl" wrote in
:

Assuming your concept was valid, i.e. signal strength was a function
of distance by some formula (inverse square), the approach to follow
is called least squares. Look around for additional info with that
terminology.

- jlw


I participate in a lot of transmitter hunts. I hadn't thought of it but
you are on to something. I wouldn't recommend finding a transmitter
using the method he wants to do it in, that would take too much time. He
would also need an attenuator to prevent full scale readings.

If he wants to hunt with an omni, all he needs really is a step
attenuator and a receiver with an S-meter. Leave the GPS at home.

A faster method is with a directional or null antenna, attenuator, map,
protractor, and possibly compass so he can put the headings on the map
more accurately.

I was thinking of using GPS too, but here is how I would do it. I have a
4 antenna doppler array that gives real time headings. The array is
mounted on my vehicle. The doppler unit sends four bit BCD to a 16 LED
heading indicator.

I would pull the BCD readings and send them to a notebook computer with a
mapping program installed and the GPS connected. The program code would
take the heading from the doppler unit, the receiving position from the
GPS, and superimpose it on the map. The code would also have an
"averaging algorithem" to throw out bad heading do to reflections and
such.

I would only do something like this to show how nifty you could find a
transmitter. Will I do this? Probably not, I already do it in my head.


KB7ADL

"Jerry L. Wahl" wrote in
:

Assuming your concept was valid, i.e. signal strength was a function
of distance by some formula (inverse square), the approach to follow
is called least squares. Look around for additional info with that
terminology.

- jlw


I participate in a lot of transmitter hunts. I hadn't thought of it but
you are on to something. I wouldn't recommend finding a transmitter
using the method he wants to do it in, that would take too much time. He
would also need an attenuator to prevent full scale readings.

If he wants to hunt with an omni, all he needs really is a step
attenuator and a receiver with an S-meter. Leave the GPS at home.

A faster method is with a directional or null antenna, attenuator, map,
protractor, and possibly compass so he can put the headings on the map
more accurately.

I was thinking of using GPS too, but here is how I would do it. I have a
4 antenna doppler array that gives real time headings. The array is
mounted on my vehicle. The doppler unit sends four bit BCD to a 16 LED
heading indicator.

I would pull the BCD readings and send them to a notebook computer with a
mapping program installed and the GPS connected. The program code would
take the heading from the doppler unit, the receiving position from the
GPS, and superimpose it on the map. The code would also have an
"averaging algorithem" to throw out bad heading do to reflections and
such.

I would only do something like this to show how nifty you could find a
transmitter. Will I do this? Probably not, I already do it in my head.


KB7ADL

I also wanted to give this link: www.homingin.com

KB7ADL



"Vince Fiscus, KB7ADL" wrote in
ink.net:

"Jerry L. Wahl" wrote in
:

Assuming your concept was valid, i.e. signal strength was a function
of distance by some formula (inverse square), the approach to follow
is called least squares. Look around for additional info with that
terminology.

- jlw


I participate in a lot of transmitter hunts. I hadn't thought of it
but you are on to something. I wouldn't recommend finding a
transmitter using the method he wants to do it in, that would take too
much time. He would also need an attenuator to prevent full scale
readings.

If he wants to hunt with an omni, all he needs really is a step
attenuator and a receiver with an S-meter. Leave the GPS at home.

A faster method is with a directional or null antenna, attenuator,
map, protractor, and possibly compass so he can put the headings on
the map more accurately.

I was thinking of using GPS too, but here is how I would do it. I
have a 4 antenna doppler array that gives real time headings. The
array is mounted on my vehicle. The doppler unit sends four bit BCD
to a 16 LED heading indicator.

I would pull the BCD readings and send them to a notebook computer
with a mapping program installed and the GPS connected. The program
code would take the heading from the doppler unit, the receiving
position from the GPS, and superimpose it on the map. The code would
also have an "averaging algorithem" to throw out bad heading do to
reflections and such.

I would only do something like this to show how nifty you could find a
transmitter. Will I do this? Probably not, I already do it in my
head.


KB7ADL

I also wanted to give this link: www.homingin.com

KB7ADL



"Vince Fiscus, KB7ADL" wrote in
ink.net:

"Jerry L. Wahl" wrote in
:

Assuming your concept was valid, i.e. signal strength was a function
of distance by some formula (inverse square), the approach to follow
is called least squares. Look around for additional info with that
terminology.

- jlw


I participate in a lot of transmitter hunts. I hadn't thought of it
but you are on to something. I wouldn't recommend finding a
transmitter using the method he wants to do it in, that would take too
much time. He would also need an attenuator to prevent full scale
readings.

If he wants to hunt with an omni, all he needs really is a step
attenuator and a receiver with an S-meter. Leave the GPS at home.

A faster method is with a directional or null antenna, attenuator,
map, protractor, and possibly compass so he can put the headings on
the map more accurately.

I was thinking of using GPS too, but here is how I would do it. I
have a 4 antenna doppler array that gives real time headings. The
array is mounted on my vehicle. The doppler unit sends four bit BCD
to a 16 LED heading indicator.

I would pull the BCD readings and send them to a notebook computer
with a mapping program installed and the GPS connected. The program
code would take the heading from the doppler unit, the receiving
position from the GPS, and superimpose it on the map. The code would
also have an "averaging algorithem" to throw out bad heading do to
reflections and such.

I would only do something like this to show how nifty you could find a
transmitter. Will I do this? Probably not, I already do it in my
head.


KB7ADL