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Old 18th Apr 2017, 15:49
  #1185 (permalink)  
dClbydalpha
 
Join Date: Jan 2011
Location: on the cusp
Age: 47
Posts: 217
Originally Posted by Pltnorway View Post
That is a very valid question.

With the radar set to 10 NM range on the PM's (copilot) NAV screen in this case, the waypoint symbol for "BLKMO" would hide the radar return from Blackrock. If using 5 NM, or even better 2.5 NM range, the return from Blackrock would be relatively larger than the waypoint symbol, and hence get your attention.

I tried this a couple of days ago (in the S92 with the Primus 701A radar) using an oil rig as "Blackrock". With 10 NM range, GMAP2, optimal gain and tilt, and at a distance of 1-2 NM from the oil rig it was very difficult to actually spot the return because of the waypoint symbol. Blackrock might have given a slightly larger return than an oil rig though.
Thanks, my beer mat calculations had Blackrock as sub tending 900m at a couple of miles (including antenna beamwidth). At 10 nm display across, then each pixel would be about 50m and so 18 pixels. Symbols are often between 16 and 32 pixels. My concern was that if a symbol was coincident with the return then it might not have been as compelling an indication as it should. Particularly if not being looked for. All built on assumptions of what display ranges were selected so just wild conjecture. Thanks for the answer.

For those calculating radar MDR remember it is not just PW but also the Receiver Recovery Time that has to be used in the calculation.
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