Old 3rd Feb 2019, 15:34
  #1004 (permalink)  
Join Date: Mar 2016
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Posts: 29
Originally Posted by ATC Watcher View Post
But Primary will not give you any altitude nor Rate of descent info, and the primary returns will also stop at a certain point , generally above 1000 ft due garbling , and where the antenna is located.
You talk a lot of sense, but permit me to correct a couple of specific points.

"Garbling" is strictly a secondary radar phenomenon - nothing to do with primary radar. It is where two separate SSR return pulse trains (from different aircraft) overlap at the receiver and hence interfere with one-another.

Also, primary radar base of cover is a lot less than 1,000'. Typically out to 50 or 60 miles it is actually below ground level, hence the ground clutter that is removed by processing (e.g. STC, MTI). See the typical primary radar vertical polar diagram below.

Of course, the actual surface conditions close to the radar will influence this, as you rightly say, but not as much so as to give a 1,000' base of cover.
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