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Radio Direction Finding

:: EPE Chat Zone ­:: ­Radio Bygones Message Board :: » EPE Forum Archives 2007-2009 » Archive through 16 March, 2008 » Radio Direction Finding « Previous Next »

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741
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Username: 741

Post Number: 80
Registered: 08-2005

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Posted on Wednesday, 27 February, 2008 - 03:29 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Is the accuracy (as opposed to range) of radio direction triangulation affected by the physical environment ?
e.g. Is an empty space better than woods or houses ?
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terry
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Username: terry

Post Number: 465
Registered: 05-2005

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Posted on Wednesday, 27 February, 2008 - 04:50 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Yes but a lot depends on frequency.

Terry
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dean_huster
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Username: dean_huster

Post Number: 244
Registered: 05-2005

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Posted on Thursday, 28 February, 2008 - 03:20 am:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

If you'd like to have some really high-resolution (e.g., direction within 2°) direction finding, build yourself a Wullenweber CDAA. They aren't portable! Nor are they inexpensive! And you need a big back yard. A really big back yard. Actually, you need a small farm.

http://www.mapability.com/ei8ic/index.html?http&&&www.mapability.com/ei8ic/rhombic/wullen.html

Dean
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ant
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Post Number: 240
Registered: 05-2006

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Posted on Thursday, 28 February, 2008 - 10:48 am:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Hello 741,

A while ago quite a few radio amateurs used a thing made by Datong, four 145Mhz aerials mag-mounted onto the roof of the car and the demo I had from a friend in Leicester was excellent, he found me very quickly despite having parked up a couple of side streets.

Many amateurs have a very active RDF sideline used in orienteering, look on the RSGB website for starters - HF and VHF.

For lower frequencies there's probably a lot of info around about the wartime stuff used for radiolocation.

Regards Ant
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hamar
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Username: hamar

Post Number: 11
Registered: 05-2006

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Posted on Sunday, 02 March, 2008 - 10:08 am:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Tracing interference to commercial broadcasts etc encountered both situations, a simple tuned dipole was the most useful of a range of antennae, you could df with reasonable accuracy then pinpoint with signal strength, open land gives excellent results and houses with re-radiating wiring is a nightmare.
ie a single complaint of interference was located 8 miles away and was obliterating reception for a whole uncomplaining village.
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741
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Post Number: 83
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Posted on Monday, 03 March, 2008 - 12:04 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Hello hamar,

That is the sort of thing I was wondering about. As I understand your post, you choose between multiple (re-radiating)possible origens using signal level: the strongest is the ultimate source.
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hamar
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Post Number: 12
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Posted on Wednesday, 05 March, 2008 - 08:52 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

741, With just one source it ultimately comes down to DF/signal strength and common sense, re-radiating wiring/metalwork makes exact pinpointing of sources very difficult by signal strength alone. Interfering sources tend to have there own characteristics, so you get close then looked for probable cause, thermostats, dimmers, even 330Kv pylons with a length of chain thrown over one of the wires once. Reducing the antennae size helps. having a pub lunch found a beer cooler affecting the rest of the village.
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drewparker
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Username: drewparker

Post Number: 26
Registered: 11-2007

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Posted on Thursday, 06 March, 2008 - 11:05 am:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Having worked with professional (military) DF equipment even with the smallest most basic aerial assembly, extremely good results can be achieved. Having numerous dipole aerials located in a circular format can be very very accurate and using more that one unit you can end up in the same room. The accuracy is more effected by the environment than you would think. Buildings always form reflections to RF energy, especially at the radar wavelengths (which is what you want) and can play havoc with DF equipment, even your GPS reciever can be adversly effected by the signal being bounced from a building before hitting your reciever. This reduces the accuracy but you will hopefully still be on the same road. With regard to range, DF gives you range advantage especially with respect to detecting radar transmissions as your DF equipment effectively has twice the range of the transmitting radar. Thus you have a pretty good idea where the bad guys are, but they dont see you. All armed forces utilise this to their advantage both during peace and conflict

Drew

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