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Direction Finding


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#1 Sn0w

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Posted 21 July 2011 - 05:40 AM

Any suggestions on DF setups or antennas? Looking around I found some interesting designs but some don't seem that practical. Adjustable is better, but currently hunting a 300-400mhz signal of unknown location.

I was planning on using something like this although I'd have to make the arms a bit shorter for my frequency (I think.)

What's needed for the multiple antenna setups?

#2 jfalcon

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Posted 16 November 2011 - 01:56 PM

Any suggestions on DF setups or antennas? Looking around I found some interesting designs but some don't seem that practical. Adjustable is better, but currently hunting a 300-400mhz signal of unknown location.

I was planning on using something like this although I'd have to make the arms a bit shorter for my frequency (I think.)

What's needed for the multiple antenna setups?


For DF, you want to have a big NULL of signal and it also to be highly directional. So if anything, you want more elements to increase directional gain or a solid reflector to create a null behind the antenna. Then you can use attenuators to mute the signal as you get closer. But the narrower the beamwidth, the better as you get closer to the fox.

I've seen some multiple antenna setups that use electronic comparison/voting. This method works by creating a phased array and detecting the minute difference between each antenna. I saw an ad on the ARRL site recently that someone built a rather modern version of this setup.

Another way would be to use A/B antenna switches. A 4 position A/B switch with directional antennas mounted to where you can align to north and have the cardinal directions covered. Then it's just the matter of being able to measure which one is stronger. A mixture of having narrow beamwidth and attenuation should at least get you close.




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