During the fist 25 hrs of my PPL in Canda, I was never once advised to switch off the Xpdr to change codes (and I was flying with a moderately young instructor).
In the UK, on about the first flight as a student, I was told to go to standby to change codes.
20 yrs ago, I used to work on avionics devpt (with special responsibility for IFF aka SSR) - to the best of my knowledge, there is no 'suppression' of code changes while the dials on your Narco / Bendix, etc are being twiddled.
ATC Babe (or 10W, if EGPK is easier for most) - if a bunch of PPRuNers were to grovel nicely, what are the chances of a look around your workplace (as I've only really done superficial tours at miltary airfields over the last 20 years). Would someone like Sandy be the best person to talk to?? We could maybe even have a Diet Coke or 2 at the Hilton afterwards??!!
