Re: Triangulation of Broadcast Signal


mwmiller314@xxxxxxxxx wrote:
How difficult would it be to track the position of a signal's moving
source?

That will depend on how fast the source is moving and how fast you can
get direction readings from multiple locations.

The situation you are describing sounds like the triangulation done on
terrestrial transmitters. If the source is not terrestrial, then it
will be impossible to separate two or more antennas far enough to get a
good triangulation baseline unless you are working with microwaves or
higher frequencies and therefore able to use dish antennas and
interferometric techniques. [Google "very large array" for more on
this.]

Directional antennas are engineered to be selective in direction for a
certain bandwidth, not highly selective for frequency. Frequency
selection is normally done 'downstream' in the electronics. May I
presume that the source will NOT be moving fast enough for doppler
frequency shifts to be significant?

Each directional antenna will be able to provide a direction towards
the source (possibly with some aliasing - you may for example be able
to determine that the soure is north OR south of you position, but not
which), valid at the moment the reading is made. If the source is
moving, those directional readings become invalid almost immediately.

A triangulation will require a minimum of two separate direction
readings from two separate positions. If one has three directional
readings imultaneously, so much the better.

If the source is moving, these readings should be as close as possible
to simultaneous to give an approximate position at the time the
readings are made.

To *track* the motion of the source, multiple triangulations need to be
made and recorded. Maps are useful tools for plotting. Plot the
location of each antenna on the map. Then plot the direction readings
from each antenna as lines passing through the antenna sites. The
source is probably close to the place where the lines intersect. A
third line for a third antenna will in general NOT intersect the same
point as the one where the first two lines intersect. You are most
likely to see a triangle. Since the source will be close to all three
lines, it will most likely be *inside* the triangle formed by the three
bearing lines.

Each approximate determination represents the most probable location of
the source at a specific time. Track the motion of the source amounts
to plotting its location as a function of time.

Tom Davidson
Richmond, VA

.

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