Today is Sunday which means northern Ontario is supposed to monitor 133.72, 128.3, 127.25, and 135.5. The freq's ARE set up, but apparently, only for transmitting and not receiving. So, I can only hear pilots within range here locally on 128.3 Does anyone else in other ATC sectors get this problem too? Is it just the contollers who don't want all pilot transmissions duplicating everywhere?
Not sure what your question really is, but it is only the controllers that can "couple" (and that's the correct term) frequencies together. Well, the technicians maintaining the equipment can too of course, and maybe they were doing just that.
Even though you could only hear aircraft on 128.3 on Sunday, the controllers can hear all the aircraft on all the frequencies. If traffic is light, it makes no difference to the controller whether the frequencies are coupled together or not. He can hear and transmit on those four frequencies simultaneously.
The advantage of coupling, (especially when it's busy) is that aircraft on different frequencies can hear each other, and don't usually transmit at the same time making it much easier for the controller.
So, when frequencies are coupled, aircraft transmit on say 135.5. The 135.5 receiver on the ground takes that signal and sends it to the ground based 128.3 transmitter near you, and voila, you hear aircraft that are actually transmitting on 135.5, but you receive them on 128.3.
Now as mentioned, there MAY have been very light traffic, and IF one controller was working all four frequencies and IF no two aircraft transmitted at the same time on different frequencies, the controller would not have been triggered to the fact that the frequencies were not coupled.
There would be absolutely no difference in the service provided. The controller continues to hear all the aircraft, and all the aircraft will hear the controller. The only difference will be that the aircraft will not hear other aircraft on different frequencies, and neither will you.