In article ,
Charlie Morgan wrote:

On Tue, 26 Sep 2006 19:40:02 GMT, Bruce in Alaska wrote:

In article ,
Sailaway wrote:

Just curious... Don't the marine radars have blanking, an adjustable
point where the radar emits no signal - so a mast wont reflect directly
back into the mast-mounted antenna? Or have masking, where the receiver
ignores returns that are too close - like from the mast or rigging?

They have "Blanking" designed into them that keeps the receiver turned
off, while the transmitter is on, and then allows a very short time
period to allow the reciver to turn back on to receive the echo from
the targets. This doesn't make the mast disappear, it just keeps
the receiver off while the transmit pusle is reflected off the
obstructions. It also doesn't keep the obstructions from attenuating
the returned echos before they get to the receiver, either.
It isn't that the mast is creating targets for the receiver to see, it
is the mast is attenuating the transmit and receive signals.

Bruce in alaska

My Furuno 1623 turns the transmit off and on, not the receiver.

CWM

Actually that is not true...The receiver is turned off, (disconnected)
from the antenna by the Transmit Pulse, as it goes thru the Ring
Circulator that connects the Receiver and Transmitter (Magnitron)
to the Antenna. Also, the Receiver LNB just behind the Ring Circulator,
on some XBand Marine Radars, is shut down by the the Transmitter Timing
Pulse, and doesn't come back on untill the Transmitted Pulse has died
off. Depends on the particular Radar Design.

Bruce in alaska
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