Zack Lau wrote:
(Washed Phenom) wrote in message om...
Partly for the fun of it, and also for practical uses, I'd like to
design a receiving system whereby a small transmitter could be
located. This would not technically be a "tracking" situation, since
the transmitter would not always be on. I'm imagining something like
a garage door opener, where pushing the button can send a brief (but
very strong if necessary - this may have power implications?) signal.
The reason I ask about the non-directional solution is because I have
access to a plot of land approx. 300 x 300 feet square, with no
restrictions on building antennas on the four corners of the property.
I'm guessing such a system could be more accurate than a directional
system at a given power level, but the technical aspects of the
situation are beyond me.
I am a mathematician by trade, but know a smattering of electronics.
It would seem, at least in theory, that the relevant parameters here
are the distances between the 3-4 antennas (would a 4th help?), and
the strength and frequency of the signal. I also realize that some
processing of the signal would need to be done at the receiving end.
Perhaps the triangulation can be handled by software?
Any advice, direction, URLs, or discussion is much appreciated.
Accurate signal strength measurements are surprisingly difficult.
Ground reflections can combine to to double the signal strength,
or nearly cancel it out. Hams and broadcasters often use the term
"picket fencing" to describe the rapid fluctuations in signal strength
that occurs with fixed to mobile signal paths.
Not that your task is impossible, just hard. Perhaps a sufficient number
of signals can be simultaneously processed to statistically reduce the
signal combination/cancellation effect to an acceptable error.
Zack Lau W1VT
Doing it by carrier phase would be better, if you could arrange a phase
reference. With hard-mounted receivers (or with a 2nd transmitter in a
known location) you can broadcast a time reference and do a reverse-GPS
sorta thing.
The higher the carrier the better the measurement, but with a lot 100
meters on a side you probably also want to send some sort of time
reference (you do get to design the transmitter as well, right?).
--
Tim Wescott
Wescott Design Services
http://www.wescottdesign.com