That's a problem for those of us with only one box. I'm thinking of my handheld on 135.475 with an earphone under one headset muff, and 135.475 on the inactive on the fixed set, to try it out.
The trial starts on Sunday February 1.
If I know fastjets are coming up the glen behind me, it'll be a bit like being a hedgehog on the motorway hearing traffic coming.