Radio oddity
Here's the scenario:
Box 1, a GNS530, tuned to Elstree, 122.400.
Box 2, a GNS430, tuned to D&D, 121.500.
Audio panel (an oldish King model) set to Auto for box 1 (i.e. listen and talk on box 1), set to "Phones" for box 2.
Press the PTT and there is loads of fairly loud background noise. Switching off "phone" for box 2 cures it. On other frequencies on box 1, eg. Brize Zone, 119.000 it doesn't happen. 122.400 is the only one I found it on.
Any thoughts as to why this is happening?