Radio direction finder

Projects General Guidance
1

Hi,
I want to ask for some input. And ideas how to tackle this.

I Have two synchronized receivers, they give out 0 to 5 Volt. I have two loop antennas connected to them so i get the form of an 8. so if i turn one antenna i get like a direction....and the voltage follows it. This is also called Watson Watt i think.

So the problem...
Can name them X and Y. For example X=2,5 Volt Y=4,7 Volt .
Y is in North-South and X is West-East

How can i calculate in witch Quadrant they are into.
I have tested with atan2(y,x) . Is that approach right? And in that case, is the result in radians? And how then get the radians to degrees?

Or is there another way to get this two analogue values to give a direction ?

Best Regards
Confused Patrik

2

You might be able to incorporate something like servos to move the antennas, as you would know the rotational position of the servos.

3

HI,
The antennas are fixed in position.
It should be possible to to a calculation, but how is a good question.
Look on old ships, they have 2 loop antennas for old system direction finding.

But i got stuck. Have done several tests. But cant get it to do the right thing. =(

4

The voltage by itself isnt enough to get direction.
You also need to measure the phase angle between the 2 RF signals from each antenna to get the quadrant info.

5

Interesting project! According to

"In the receiver, the bearing angle can then be computed by taking the arctangent of the ratio of the N-S to E-W signal."

Unfortunately I am not a math wiz but I'm am very curious to see how this works out.

6

sm6tbe:
I Have two synchronized receivers, they give out 0 to 5 Volt. I have two loop antennas connected to them so i get the form of an 8. so if i turn one antenna i get like a direction....and the voltage follows it. This is also called Watson Watt i think.

So the problem...
Can name them X and Y. For example X=2,5 Volt Y=4,7 Volt .
Y is in North-South and X is West-East

How can i calculate in witch Quadrant they are into.
I have tested with atan2(y,x) . Is that approach right? And in that case, is the result in radians? And how then get the radians to degrees?

Not sure on that particular function (atan2), but the arctangent is the correct function. And by definition, it should output in radians. Radians to degrees is multiply by 180/? You need however to research the reference material for whatever library that is in.

I think your concern will be the encoding of the input voltages. If they are generated as 0 to 5V, then you would need to measure them and then adjust that value - multiply by a scale factor - to a signed variable.

You cannot determine the quadrant with only loop antennae. If you can move them, you can use this to determine which pair of opposite quadrants the direction is not.