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Old 19-10-2013, 20:49   #1
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Radio Directional Finder

Anybody know when these things were last used?
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Old 19-10-2013, 20:50   #2
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Anybody know when these things were last used?
I think the Germans were bombing London at the time lol

Dave
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Old 19-10-2013, 21:13   #3
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Re: Radio directional finder

Depends on what frequency range you're looking for but I'm sure the military is still doing it.
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Old 19-10-2013, 21:26   #4
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Re: Radio directional finder

Think I last used one in the early to mid 80's.
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Old 19-10-2013, 21:49   #5
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Re: Radio directional finder

We had one. Don't remember what happened to it. I need the space to add a 100 watt receiver to power the exterior speakers. Had several frequences and a antana that rotated for the best reception which was the direaction it was from.
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Old 19-10-2013, 22:31   #6
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Re: Radio directional finder

Found an info sheet dated in 2006 for a system that seems could be used. But like I said, it depends on what you're looking for.

Something else I just thought of is how personal locators are setup with dual frequencies. One for whatever satellite system receives the signal and another one for rescuers to home in when getting closers. At least that's how I understand it.
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Old 19-10-2013, 22:32   #7
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Re: Radio directional finder

Pretty much every SAR vessel and craft uses them. How else do you think they find EPIRB's when they go off.
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Old 19-10-2013, 22:44   #8
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Re: Radio directional finder

In the old days prior to GPS one could use a little cheap portable radio with a simple built in directional antenna. You could dial in a known station and turn the radio(rotate) until the signal was very weak or none at all and you found the null, in other words you were pointing at the station.
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Old 19-10-2013, 22:46   #9
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Re: Radio directional finder

Did some hull repairs to a new Queensland Police Force Patrol vessel (aluminium) they had a room dedicated to RDF (off limits) just for the purpose Greg dpeaks of.

Also most animal tracking researchers in the field use them to locate furry things for David Attenborough.....
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Old 20-10-2013, 00:13   #10
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Re: Radio directional finder

Quote:
Originally Posted by caracas View Post
Anybody know when these things were last used?
I had one on board for several years. It worked well. If you knew the lat/lon of specific radio antennas and had 2 different stations being received, you could determine a very accurate fix. I tossed it because GPS chartplotting was so much simpler and generally more accurate because it takes the human doing the math out of the equation.

Aircraft of all sizes military and civilian use radio direction for navigation.

Bill
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Old 20-10-2013, 00:15   #11
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Re: Radio directional finder

Built one from a kit for my Dad's Columbia Defender in the 1960s.
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Old 20-10-2013, 00:24   #12
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You can still use them: all the charts still list the airport beacons.
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Old 20-10-2013, 00:29   #13
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Re: Radio directional finder

I have one in the garage that will go on the boat when we buy one next year hopefully.

The only thing I don't understand about it is the sense antennae. The radio didn't come with instructions and I haven't been able to find them on-line.

I also intend to build a handheld Yagi antennae for VHF so I can radio direction find other stations or anyone that goes overboard with a handheld on their person. Not sure how well that would work, but better than nothing.
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Old 20-10-2013, 01:10   #14
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Re: Radio directional finder

Bermuda still has some AM radio stations. Rotate a cast iron frying pan around your portable radio, and when you lose the signal, that the direction to the antenna. Gospel around here is to not go over the horizon without the frying pan.
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Old 20-10-2013, 01:37   #15
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Re: Radio directional finder

[QUOTE=Adelie;1369240]I have one in the garage that will go on the boat when we buy one next year hopefully.

The only thing I don't understand about it is the sense antennae. The radio didn't come with instructions and I haven't been able to find them on-line.

I also intend to build a handheld Yagi antennae for VHF so I can radio direction find other stations or anyone that goes overboard with a handheld on their
Is it ADF or RDF? Frenesi had an RDF. The null signal is easier to hear the minimum as opposed to tuning for the max signal. Choose your freq, rotate the antenna until you get a null, adjust the gain as necessary to get a good null, read the bearing. The antenna was marked with an arrow. An ADF you push a button and the antenna rotates until the electronics finds a null.
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