And, is it necessary to give callsign on every transmission? Establish comms, yes. Two way established, not necessary. When handed over after a long period of two way, is it necessary again ? My CAP 21 well worn & after 38 years. I thought I knew it all but got a right old chewing out on yesterday's Line Check ! ATC told me " Continue now with.....on......." I kept saying, for example, 'Frankfurt on ......, cheers mate, have a good'n". Oh and finally, Checker admonished me for continually saying "Roger, wilco". He told me that "Roger " means, I understand & will comply. "Wilco" means I will comply. So, I was saying, in effect, " I understand & will comply, I will comply", followed by a unruly "Cheers mate, have a good'n". Oh dear. Nearly grounded for R/T refresher Training. Think the flying went ok though !