Can't say I've ever been distracted by practice pans, training fixes or any other "abuse" of 121.5 whilst monitoring it whether in the UK or anywhere else in the world. What I do get slightly frustrated at is the ear splitting squeal that erupts from my headset when someone is still making their PA, passing their arrival information or calling maintrol and 20 muppets all jump on the transmission to say "You're on guard". If you're one of the self-appointed guardians of 121.5 then perhaps you should go back and revise the operation of airborne transmitting/receiving equipment - if someone is still transmitting
they cannot hear you - on a similar note if more than one of you transmits a reminder simultaneously once the original miscreant has finished -
you block each other out and they still can't hear you. Keep up the good work
