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Registered Member #4266
Joined: Fri Dec 16 2011, 03:15AM
Location:
Posts: 874
Hi I'm trying to workout how to do direction finding. I'm planning on have two antennas 100meters apart, and would like to go in a straight line away from the two antennas. What confuses me is that if the speed of radio waves are fast, how would you workout the difference from each other at 100meters distance.
Done some more searching, if there are 6 antennas spaced to fill 100meters, and each antenna gets a delayed signal which repeats along the line, some how that might beable be used to workout the direction?
Registered Member #72
Joined: Thu Feb 09 2006, 08:29AM
Location: UK St. Albans
Posts: 1659
It also depends on practicalities like, do you want your array of antennas to be transmitting, and you have a hand-held receiver that tells you position, or are you trying to locate a single transmitter with your array of receivers.
Perhaps the lowest tech way of doing the latter is to use a circular array of receviing aerials, and a rotary switch commutating each into a single reciver. If your transmitter is trasmitting CW, or anything actually but CW allows the lowest tech solution, then your effectively rotating receiver antenna will superimpose FM on the received signal. Compare the phase of the demodulated FM with the phase of the switch signal that is commuatating your array, and you have the angle. This is called pseudo-doppler. It even permits an all-analogue solution. Look up 'commutating array DF' or some such. In thje bad old days, they actually used a motor-driven rotating switch, but these days, diode switches or 8:1 IC signal multiplexers work rather better.
There are quite a few other ways of doing it as well.
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Direction finding
