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From: "Ken Taylor"
Subject: Re: Radar basics?
Date: Thu, 17 Oct 2002 10:40:19 +1300
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wrote in message
> Ken Taylor wrote:
> > You could certainly receive the radar signal being directed toward you,
> > it would not mean anything - you wouldn't receive the signal of a target
> > which happened to be illuminated at the time, and you certainly wouldn't
> > receive such signals from any other direction (with any certainty about
> > was illuminating them, or when). Unless you got *really* clever and
> > identified the RF signature of each transmitter.....(mind starts to
> > at the garage full of home-brew equipment at this stage!).
> I am not sure about this, but it seems to me that as long as you are
> reasonably close to the airport it may be doable...
> The scheme would go something like this.
> You use a recever with its aerial pointed at the airport to listen for the
> beam scanning over your location, this gives you a reference for rotation
> speed and also (as many pulses will be receved (at varying signal
> a timing reference for the transmitter. Lock one PLL onto the airport
> scan speed and another onto its pulse rate (may need some kind of gating
> Now you have information about where the airport transmitter is pointing
> at any given time, you point your main aerial in the same direction, and
> use the timebase derived from the pulse rate PLL to allow a display to be
> Another interesting variation would be to try the same trick with marine
> radar. This would allow a radar image to be generated without needing to
> radiate from your ship.
> Sounds like a nice little project to play with to me!
> Regards, Dan.
Hmmm, I thought briefly about it and thought along those same lines, but
dismissed it as 'too difficult'. On reflection (pun intended!) it's probably
'not trivial' but as you say, 'doable'. You don't actually need to rotate
your own antenna, if you're prepared to accept some error in your display
(on the assumption you won't get an exact fix anyway, as you don't know the
exact az/el of the transmitting antenna). However there's the possibility
that the other radars in the area may make it pretty hard if they are
coordinating with each other to minimise interference. Determining range and
bearing will still require an amount of maths, but that's what PC's are for!
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