Andrew,
There is RADAR and RaDaR. After a 40 year delay all of the S.F.
Bay Area non RADAR airports have a TV like system called BRITE. Bride does
give the towers a TV like screen that allows the tower to see the VFR
aircraft on radar with a readout of altitude.

The antenna is usually so distant from the airport that it is not certified
to provide a transponder code nor separation. I recently checked out
Concord, CA tower's situation and found that the radar is a two edged blade.
In over 40 years as a radar-less tower there has never been an ATC related
accident at CCR. Nor has there been one in the year BRITE has been in the
tower.

The problem is that some of the tower people become reliant upon
a radar screen that has inherent weaknesses and errors. The visual
skills of the past become less required and proficient. The position
reporting skills of the pilot become more important.

A week ago I was with a student in a C-172 where we made a call-up saying
that we were planning on a 45 endtry to the downwind. Immediately
afterwards a twin Commander made the same call. Neither aircraft was able
to find the other and the controller could not distinguish one from the
other since both were squawking 1200. The difficulty arose from the
perception of what constitutes a 45 entry. The Commander was closer to a
direct entry to downwind than a 45.

By making a short approach we were able to help resolve the situation.

Gene Whitt