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» Online Classroom   » Radar   » Public Discussion of Marine Radar   » Interference Rejection for RADAR

Author Topic: Interference Rejection for RADAR
Daniel Paschmann

 - posted August 06, 2005 10:57 AM      Profile for Daniel Paschmann           Edit/Delete Post 
Dear Forum, dear David,
In your "Radar for Mariners" we learn what IR is for.
I like that book a lot because for any topic you provide pros and cons. Not so for IR. There doesn't seem to be any particular disadventage.
My question is: If so, why don't just leave it on in general? Why is it to be switched on or off if it only helps?
Regards from Karlsruhe Germany,

David Burch

 - posted August 06, 2005 11:08 AM      Profile for David Burch           Edit/Delete Post 
Yes that is the case, some people just leave it on. However, it may reduce sensitivity to weak targets and it may interfere with the detection or identification of racon signals. I thought the latter point was mentioned in the book. I will look around for that and also think more on this good question and follow up shortly.
From: Starpath, Seattle, WA
Daniel Paschmann

 - posted August 08, 2005 01:03 AM      Profile for Daniel Paschmann           Edit/Delete Post 
Dear Starpath,
When I asked this question which came up in chapter 8 I hadn't read chapter 9 though.
You do very well explain the effect on receiving racon signals in the latter chapter. That's what I expected anyways :-)
Thank you very much.

David Burch

 - posted August 08, 2005 10:20 AM      Profile for David Burch           Edit/Delete Post 
In looking into this, it seems I should have had more detail on this valuable point that you have brought up. Consequently, i will add a section to the Errata that covers this, as well as SARTs, which were not covered in the text.

Looking ahead to that, the weaker targets i refer to could also in fact be rather strong targets that are just not seen often due to high seas. If a target just returns a few echos per sweep or none at all it will look like interference and thus if IR is on, will not be displayed. In other words, looking for a distant ship in a seaway, the IR could stop you from finding it completely.

Also, and maybe more important, i should have also stressed that IR on can shut off completely the detection of Search and Rescue Radar Transponders (SARTs). For now, here is link to a commercial source (from UK) of these with some description, S.701 SART imported by Negron marine. See also this US model from ARC Pathfinder SART, which includes manuals and specs to download.

And here is a pdf note on radar adjustments to optimize SART detection. I am surprised to see that the IR function is not mentioned in it, but it should be turned off. This is actually an IMO update to an earlier report, which i am looking for.

From: Starpath, Seattle, WA

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