RadioBanter - View Single Post - Non-directional tracking solution?

May 27th 04, 05:25 AM

(Washed Phenom) wrote in message om...

Any advice, direction, URLs, or discussion is much appreciated.

Thanks for the replies so far. They've been helpful, and have sent me
on some interesting Google searches learning a lot about RDF in
general. Some more specifics:

I have no preferred frequency ranges, but that is more out of
ignorance than flexibility! In terms of transmitter power, in my
first post I mentioned that a continuous signal wasn't necessary if
that would help matters. It seemed plausable to me that a transmitter
which used its power to transmit a short, strong signal could be
detected at a much longer range than a weaker signal.

The reply regarding carrier phase was interesting, and sent me on a
tour of GPS basics. Half the fun of this project is going to be
learning new stuff. As I understand it, the reason you called this a
"reverse GPS" is because the multiple receivers are in known locations
instead of multiple transmitters. It would be feasible to build a
second transmitter (a time reference?) and place it somewhere in the
100 yard square. There is a house roughly in the center of the
property which would be where the "guts" of the processing equipment
would be anyway. How does the carrier phase solution compare to VHF
and shortwave in terms of power requirements, size of transmitter,
etc?

Just to get a better sense of whether the range and resolutions I'm
looking at are feasible, suppose you wanted to locate your local
college radio station's transmitter. I just googled a few college
stations and found two FM stations that transmit at 300 and 400 watts.
The 300 watt station claims to cover 700 square miles. Of course I
realize that: 1) "covering an area" may not be equivalent to "area
within which their location can be pinpointed", and 2) Even if I could
generate such power in a portable transmitter, I would need to choose
bands so as not to run afoul of the FCC. (Just how much transmitting
power can be generated from a garage door sized unit is another issue,
and another reason the brief "burst" signal sounded preferable).
Anyway, I was sidetracked there. To get back to the main question, if
you had antennas at 4 corners of a 300 x 300 ft square lot, are there
any good thumbnail estimates of how accurate you could be at locating
the 300 watt college station, and how this accuracy varied as a
function of the distance to the station?

In addition to being a fun way to learn new things and tinker with
electronics, this project is also motivated by someone I care a great
deal about who often works in isolated outdoor locations and doesn't
own a cell phone or GPS. I know when she is at these sites, but worry
she will be unable to call for help if something happens. Can she be
located by her pushing a button and at what range?

She's already suggested building a Bat-Signal, but that is beyond by
technical expertise. Also, she said that buying her a cell phone and
GPS would be cheaper than building this monstrosity, but I like
intellectual challenges and need to keep my mad scientist reputation
well-exercised.

Thank you again, and please continue the excellent discussion.

-wp