Sorry to ask but having been in the avionics biz in Europe for forty years I had never come across a VHF usage for SELCAL. The whole point of SELCAL is that it enabled flight crews to monitor an assigned HF frequency without having to listen to all the noise and crap associated with HF reception and / or where over-zealous use of a squelch control could desentitise the radio to the point where no reception was possible.
What possible use is there for SELCAL on VHF?
Surely in order to develop a mental picture of traffic in say a 500 nm diameter circle around a ground transmitter and indeed to comply with all current VHF communication practices crews should be actively monitoring the frequency of that ground Tx. and not just listening out for specific calls to them.
Background noise associated with VHF comm is automatically squelched out or muted by the signal-to-noise squelch circuits in the airborne Tx / Rx, these being overridden only when the Carrier squelch circuits preset values are exceeded so the airborne RX should be quiet until a proper signal overides the squelch. With an active SELCAL applied to an assigned VHF frequency isnt there the possibility of flight crews missing other transmissions not intended for that specific aircraft but nevertheless providing info to the crews about other aircraft in the vicinity.
Maybe I'm being a little thick but to me SELCAL on VHF seems to be retrogresssive idea... can someone ptease explain... this is not intended to be argumentative, just looking for a justification...
Thanks,