Originally Posted by
magpienja
Hi HD...yes vertically polarized so Omnidirectionally.
Its crossed my mind that once at cruise alt the North America bound aircraft communicate via there data link....odd that they dont report QSY the freq.
Squawk 6042 may well have it - If flights are operating CPDLC then you won't hear a voice "QSY" (I'm not a radio amateur but I believe that means a read back of frequency going to? as in "contact Shannon on ...")..
How it works with CPDLC on board is that the new frequency gets sent up to the aircraft by datalink, the crew do a datalink acknowledgement of that change and then they switch frequency, no voice call on the old frequency, onto the new VHF freq.
Once you get to the new frequency you still check in by voice, and then if still CPDLC you may well go silent again ( as far as VHF voice is concerned)...
All the above may well explain why you are only hearing traffic on the initial call as they enter the sector you are listening to.