Tim, this is simply not correct. It is the other way around. Our club
recently invited a controller from norcal approach to talk on this
very subject, and he confirmed they vector traffic arround any mode c
target they have, regardless if they have radio contact. The radio
communication only makes their job easier, but they very much prefer
you would fly with transponder than without one even if you don't talk
to them. Of course, if you enter class B,C, or D airspace you must be
in radio contact.

Ramy


On Mar 7, 11:52 am, "Tim Mara" wrote:
"If we continue to fly in these heavy traffic areas, even with a
transponder, but do not stay in communications with ATC it's hardly better
than being there without a transponder.