"Steve Lusardi" wrote in
:

The
restriction at close range is Pulse width and receiver turn on time. A
RADAR mile is 6.36 micro seconds. If you want to see a target 100
yards in front, the RADAR set must transmit a pulse and turn on the
receiver to catch the echo in less than .31 micro seconds. That's a
very tall order with a magnetron, as they are not gated. They operate
by dumping high voltage on the cathode, which rings the hell out of
the cavity. They turn off when the cavity decides it no longer is
excited and the receiver can not turn on until there is no more energy
being emitted from the magnetron. This is becoming a very big issue in
Europe at the moment. There now is a new commercial regulation as of
Jan. '06 specifically pointed at canal traffic that stipulates that
all new RADAR sets work at 50 meters. For exactly the reason you
mentioned in your post. Now that's tough to do. Steve


Before the water in the dome rots the hell out of the Raymarine radar on
Lionheart, that little sucker can see the 4th boat down our dock on the
1/8 mile range! It even plots the dock correctly from our 20' antenna
on the mizzen. Pulse width must be picoseconds. I don't think it ever
gets very wide to keep resolution high and current drain low. Hell, the
scanner cable to the RL70CRC display where it gets its power from has
very small, long power conductors and most of the power has got to be
heating up the maggie filaments. I had a helluva time explaining to
some captains why a 2KW radar didn't draw more than 2KW off their
batteries. Some of them were afraid to turn 'em on without the engine
charging all that power!...(c;

AIS to the rescue! Need shore fixed stations with all up-to-date
obstruction data coming out of them....