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Radar Arc's and blips, the answer
On Tue, 23 Dec 2003 13:30:49 -0500, "Leanne" wrote:
Larry, We those pulses a CQ????? :-p Leanne W1WXS s/v Fundy Not enough power for SETI. Larry W4CSC NNNN |
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Radar Arc's and blips, the answer
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#3
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Radar Arc's and blips, the answer
We used to point them at the moon and pulse them, manually,
while feeding a signal generator into the test repeater (display) so it would keep sweeping. That way you could count the number of sweeps and measure the distance to the moon! You could actually measure the difference over time in the moon's distance with it. Cool stuff. Larry, We those pulses a CQ????? :-p Leanne W1WXS s/v Fundy |
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Radar Arc's and blips, the answer
On Tue, 23 Dec 2003 06:46:41 -0500, "Jeff Morris"
wrote: As I recall, the spec mentions sidelobe energy at something like -20dB. That seems like a big reduction, but when I'm passing a large ship at several hundred yards, that's still a lot of energy bouncing around. Thanks, -jeff I remember a couple of powerful radars you had to turn off if you were coming too near a reflective object, like driving by another ship in a channel. There was so much power reflected back, the stupid things would blow their OWN receivers! Navy used to have a huge air search radar, AN/SPS-30, easily identifyable because of its huge round dish with giant "arm" out in front to hold up the big waveguide and feed horn. It ran so many megawatts it would cut seagulls out of the air, cooking them in flight. We used to point them at the moon and pulse them, manually, while feeding a signal generator into the test repeater (display) so it would keep sweeping. That way you could count the number of sweeps and measure the distance to the moon! You could actually measure the difference over time in the moon's distance with it. Cool stuff. Larry W4CSC NNNN |
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Radar Arc's and blips, the answer
As I recall, the spec mentions sidelobe energy at something like -20dB. That seems like a big
reduction, but when I'm passing a large ship at several hundred yards, that's still a lot of energy bouncing around. Thanks, -jeff "Steve" wrote in message om... Hi Jeff; I don't know if you got your answer yet or not what I learned from the Navy. Your radar sends out a fairly directional beam of energy straight out the front of the antenna, then receives the reflection of the other ships (usually large and metal) and shows you the blip on the screen. Ideally that's all you'll see. But radar antennas aren't perfect and they also transmit a tiny bit of energy off to each side of the main beam at about 45 degrees relative to the main beam. So the arc you see starts as the first lobe sweeps the big ship and the antenna sees that as the beginning of the arc. Then the main beam sweeps the ship and you get your blip. Then the other lobe sweeps the ship and that's the arc on the other side of the blip your seeing. This all happens as the antenna is rotating pass the large metal ship. Well I hope that helps. Steve Hicks |
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