Actually, one thing I was wondering after I got the alert about the 7700 (via flightradar24) - is there anything I'm missing in terms of a reasonably reliable way to figure out what Center frequency a given airplane is currently communicating on, when not low enough to be talking to Approach? I'm assuming there isn't, because handoffs from departure seem to vary frequencies when I fly.
You would need charts that show the different sector boundaries and their altitude or flight level stratums. Sectors can be combined, so you might be given a different frequency in the same area at different times of the day and/or days of the week.
With Approach, sector boundaries can also change depending on which runway(s) they're landing.
You could potentially call up the facility and ask for copies of the sector charts, but I don't know what kind of response you will get.
Right now due to COVID-19, facility tours are not allowed, otherwise you could see ATC in-person and ask to take a look at their charts then, as well as ask the Controllers any questions, workload-permitting.
The facilities that I've worked at (HCF Center and Houston Center) have been happy to give tours, but they have to be during normal business hours, and you have to be a United States citizen. For a tour, I suggest organizing a group of pilots or others interested in aviation, rather than just going by yourself.
The views expressed here are my own and not necessarily those of the FAA.
