nigelh
Shy ..can they use radar even if you Txsponder is off ? I would have thought there would be so many places they lose contact if you are v low that it would be impossible to prove the contact was you ? This of course adds greatly to safety
as we will all now be turning ours off when going low level 
I agree with you. But you do not have to switch off the transponder, just de select mode "C" when low level.
