A small commercial marine radar that runs off 13.6vdc may only use 40watts
average power, but the peak pulsed power from the magnetron is huge.  Alot
of the newer units have TX up and the majority of the circuitry is on the
mast.  Military radars are classified as surface search and air search.
Taking a marine band surface search radar and using it to find airplanes
just doesn't work out all that well.  You would need an antenna designed for
the job, for example an "orange peel" antenna.  All I can say is that it
would be a monumental project.  The performance of the system would be no
easy task and I'd not sell it to anyone as I'd be afraid of someone running
into another plane under IFR conditions and then sueing you for any money
you previously made and may make in the future.  There must be some catch,
otherwise Furuno would be making them.
Mike
----- Original Message -----
From: "David VanHorn" <dvanhorn@CEDAR.NET>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Sunday, August 05, 2001 1:13 AM
Subject: Re: [EE]: Amateur radar?


> At 09:01 PM 8/4/01 -0400, Sean Breheny wrote:
> >Hi Dave,
> >
> >I've got to ask: why do people use marine radar on cars?!
>
> Because they don't make radar units for cars.
> :)
>
>
> >First of all, my primary interest was toward the aircraft side (I think
> >it would be REALLY amazing to have a display on your computer screen in
> >real time of all the aircraft in, say ,a 30 miles radius!) so my ideas
> >may not be as relevant to the weather version, although that interests
> >me, too.
>
> Probably similar application.
> I think doppler is out of the reach of the hobbyist, but a good look at
> storm structure would be achievable.
>
> >I was thinking of using a bunch of Mini circuits ERA amplifiers in
> >parallel (with hybrids to combine power) as the output amp, providing
> >only around 100mW depending on how many I wanted to parallel.
> >Since these can be had for only a few dollars a piece and go up to about
> >20mW power. Some similar parts from minicircuits would also
> >make a nice LNA for the receive side.
>
> I can check with my local microwave ham, I'm sure there are simpler
devices
> to hack.
>
>
> >I would mount an upconverter and a downconverter right up on the back of
> >the antenna (probably a small dish). I would feed the TX signal and RX
> >signal to/from the converters with regular coax, using a baseband of
> >about 1 MHz.
>
> I'd be inclined to go with 70 MHz, and use TV receiver components
>
> >  Since A to D and D to A converters can easily sample at several
> >megasamples/sec, the outgoing signal could be generated by a D to A
> >connected to a high-speed DSP chip, and the incoming signal could be
> >processed by an A to D and another DSP chip. This way, a change of coding
> >scheme or decoding algorithm would be only a software change. I'm fairly
> >certain this would work for simple pulses, but I'm not sure if DSP chips
> >have enough horsepower for doppler extraction from pulse compressed
> >coding schemes (like Barker codes) which we might need to make up for the
> >low output power.
>
> Interesting.
>
>
> >Finally, some PICs could be used to control steppers or other servos to
> >tilt the antenna horizontally/vertically. I was thinking of using
> >something around 5GHz, so a relatively small dish (perhaps a 2 to 3 feet
> >diameter) could be used.
>
> Makes sense.
> I'd like a small beamwidth to get high resolution.
> This is one problem with marine radars. They have a thin but tall fan
beam,
> because ships roll around a lot. That makes them less than stellar for
> mapping clouds, where things change with height.
>
> 10 or 24 would shrink that antenna, but I don't know yet what the rain
> attenuation would be like.
>
>
>
> --
> Dave's Engineering Page: http://www.dvanhorn.org
>
> I would have a link to http://www.findu.com/cgi-bin/find.cgi?KC6ETE-9 here
> in my signature line, but due to the inability of sysadmins at TELOCITY to
> differentiate a signature line from the text of an email, I am forbidden
to
> have it.
>
> --
> http://www.piclist.com hint: To leave the PICList
> mailto:piclist-unsubscribe-request@mitvma.mit.edu
>
>

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