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?

Sailaway wrote in news:FX_Rg.4099$KF6.3557
@newsfe09.lga:

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?


no...... in fact, not too many shorebased sets do either although some will
have a setup where the actual picture is blanked out.

Sailaway wrote in news:FX_Rg.4099$KF6.3557
@newsfe09.lga:

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?


otnmbrd wrote back:
no...... in fact, not too many shorebased sets do either although some
will have a setup where the actual picture is blanked out.

Interesting. I brought it up because way back when I was in the Navy *A
school* for avionics I remember learning about those things. Never
worked on radar though, except the ancient ones in the school.

On Mon, 25 Sep 2006 22:23:01 -0400, Sailaway
wrote:

Sailaway wrote in news:FX_Rg.4099$KF6.3557
:

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?


otnmbrd wrote back:
no...... in fact, not too many shorebased sets do either although some
will have a setup where the actual picture is blanked out.

Interesting. I brought it up because way back when I was in the Navy *A
school* for avionics I remember learning about those things. Never
worked on radar though, except the ancient ones in the school.

You may be thinking of the T/R cell which shorts the receiver out
during transmitter pulse time.
Then a swept gain control shapes the receiver gain with distance -
low for near targets, high for distant ones

Brian Whatcott Altus OK

otnmbrd wrote:
Sailaway wrote in news:FX_Rg.4099$KF6.3557
@newsfe09.lga:

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?


no...... in fact, not too many shorebased sets do either although some will
have a setup where the actual picture is blanked out.

My Ray SL70 appears to have blanking set at 25 yards, though I can't
find it in the specs. I'll be talking to a tech soon and I'll ask him
about that.

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
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