-- You really only need two receivers. The receivers have directional antennas connected to them, and the antennas are pointed at the target so that the input signal to the receiver is maximized. Then, when that\'s done, if you draw a line from each antenna in the dirction in which it\'s pointing, where the lines intersect is where the target is.
Actually, because nulls in the antenna pattern are much sharper than the lobes, you usually adjust the antenna for minimum signal. But the principal is the same.
I guess this is not really a electronics question but some of you guys may know this anyway.
I was wondering how to triangulate a radio signal. I understand that you would need three recivers at least. But how do you measure it and get the exact position? Do you check the diffrence in time at each reciver since it takes some time for the radio signal to travel?
Anders N.Vinje
-- Principle.
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What are you trying to do? The above posters mentioned signal strength methods to determine direction to a source. This works, sort of, it's a 20th century method. If there is modulation on the RF carriers that can be precicely timed, accuracy can be much greater than the direction finder method.
Imagine two receivers, or three or even four, each with a very accurate clock. Now imagine that there is a detectable event in the modulation like the start of a frequency or note pattern that is detected at each receiver. Each receiver notes the precise local arrival time of the event and from that calculates the difference in distance to the source between it and the other receivers. From these distances, circles of distance from each receiver can be plotted. A vector or direction from each receiver can be calculated from the circles and these vectors, in turn, intersect where the transmitter is located. This can be very accurate depending on the time resolution. Ten nanoseconds of time resolution will give an accuracy of 3 meters in location.
This is the way GPS works only there is one receiver and several satellite transmitters but the priciple is the same. The precise timing and event marking are in the coding of the transmitter modulation patterns and a microprocessor does all of the required calculations and generates a display.
A crude system working on these princilpes could work on any radio signal. The receivers would need some electronics to establish the time base and to detect radio modulation events. A simple readout could display the local event time and one could manually plot the circles and vectors on a map to determine location from these readouts. I suppose this is way beyond what you want to do. Bob
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