From: Keith Wootten
Subject: Re: Radio Direction Finding
User-Agent: Turnpike/6.02-U (<7r9OMDU2ooRJCQmjnYJxyjtHfm>)
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Date: Wed, 6 Nov 2002 09:28:33 +0000
NNTP-Posting-Date: Wed, 06 Nov 2002 09:28:36 GMT
Organization: ntl News Service
In message <firstname.lastname@example.org>, Frank
>It would help to understand why you have this constraint.
>How much smaller?
Handheld, pocketable, rugged. Has to work over ~30 metres with
licensable power. I don't want to use a voltage probe primarily for
aesthetic reasons and also because of their sensitivity to interference.
I suspect it's not feasible, otherwise I would've found some reference
by now, but it's always worth running these things past others.
>Without more details on your application, it's hard to develop a good
>design assumption; however, I suggest you look at TDOA (time delay of
>arrival) and doppler methods. A TDOA system can work very well with
>antennas smaller than 1/4 electrical wavelength, at the expense of
>efficiency. A TDOA system can be implemented by switching two antennae
>/ RF amplifiers at the reciever, and using the output of the receiver
>phase detector to adjust a servo that dynamically adjusts antenna
>position. There is no ambiguity but the drawback is that the antennae
>rotate via servo. For a stationary, but slightly more complicated
>solution, use the doppler.
Thanks, I'll have a look at TDOA, although my size constraints would
make the time difference (thus phase) rather small.