I made a flight plan from Sandspit CYZP to Vancouver Int CYVR. Immediately after takeoff at some hundreds feet altitude I could contact Vancouver centre and have a request for flight following approved.

But wait this makes no sense since the center uses a VHF frequency. And such frequency bands only have line in sight range. So how could a possible talk to a controller when Vancouver is some 400 nm away ?
 

Since you are in the Sim and not real life,......anything is possible.  Now if the frequencies were UHF, I would say you'd have to be up at cruise altitude and range would be about 200 miles.  VHF frequencies may travel a bit farther, depending on transmitter power.  HF frequencies are "global".

Air Traffic Control Centers have remote transmitters throughout their designated coverage area so that they can communicate with aircraft wherever  they may be. I live in a city that is under New York Center airspace. Although the actual controllers are on Long Island, 150 miles from here, one of their remote radio sites is just 10 miles east, and I can easily hear both sides of ATC comms, (pilot and controller), on a scanner at my house.

According to ForeFlight, Sandspit airport has a nearby Vancouver Center remote site, operating on 133.675

There are multiple (20+) Center frequencies located all over BC. You could contact them on the ground at CYZP irl.

19 minutes ago, JRBarrett said:

Air Traffic Control Centers have remote transmitters throughout their designated coverage area so that they can communicate with aircraft wherever  they may be. I live in a city that is under New York Center airspace. Although the actual controllers are on Long Island, 150 miles from here, one of their remote radio sites is just 10 miles east, and I can easily hear both sides of ATC comms, (pilot and controller), on a scanner at my house.

According to ForeFlight, Sandspit airport has a nearby Vancouver Center remote site, operating on 133.675

On a ILS RWY 12 procedure I have for Sandspit it says APP/DEP Vancouver/Centre 133.4. Are those remote transmitters operating on slightly different frequencies ? Or are they relay transmitter on the same frequency ?

The repeaters are called Peripheral Stations (PAL). When located at airports, they'll be listed under airport comms.

E.g. https://skyvector.com/airport/CYPR/Prince-Rupert-Airport

You'll also notice Remote Communications Outlets (RCO) which are repeaters for FISE and FSS. 

 

32 minutes ago, jfri said:

On a ILS RWY 12 procedure I have for Sandspit it says APP/DEP Vancouver/Centre 133.4. Are those remote transmitters operating on slightly different frequencies ? Or are they relay transmitter on the same frequency ?

 They are different and belong to different sectors. 133.67 being low level (FL280 and below in this area) and 133.4  above FL280. 

Edited September 6, 20196 yr by Dave_YVR

16 hours ago, Dave_YVR said:

 They are different and belong to different sectors. 133.67 being low level (FL280 and below in this area) and 133.4  above FL280. 

A similar situation locally with New York Center. The Elmira sector low frequency is 133.350. That is the remote site in nearby Sayre, PA which is easily heard here using an outside scanner antenna. The Elmira high sector on 132.175 is on Elk Mountain in Pennsylvania, which is 50 miles east, so I cannot monitor the controller, but I can easily hear aircraft in flight using that frequency. All of the NY Center remote sites also have an assigned UHF frequency for communicating with military aircraft.

The various remote RGAG sites are connected to the actual center on Long Island using leased telephone circuits.

Even our local airport remotes some of their transmitters, since the airport is in a valley, surrounded by hills on all sides. The transmitter and antenna for the ground control frequency is on top of the tower cab, but the transmitters for approach and departure are on a hill south of the airport to give increased range.

Aren't the ATC centers in FSX sort of ATC on steroids, due to Flight Service Stations not being supported? I mostly fly in the same region jfri mentions and I'm often surprised I can contact Vancouver center in certain areas; surprised even though I'm aware of relay transmitters and remote transmitters. In this region for VFR flights there's locations where I should be contacting NAV Canada's Flight Service Station in Kamloops, but I've never had that option. I've just assumed FSS aren't supported and that's why.

I've also noted that VATSIM network works on the same premise; everything is managed by a real person Vancouver ATC (CZVR) controller and they need you flying at 15,000 ft anywhere in the province in order to track you. 

Edited September 9, 20196 yr by Kronovan

15 hours ago, Kronovan said:

In this region for VFR flights there's locations where I should be contacting NAV Canada's Flight Service Station in Kamloops, but I've never had that option. I've just assumed FSS aren't supported and that's why.

I've also noted that VATSIM network works on the same premise; everything is managed by a real person Vancouver ATC (CZVR) controller and they need you flying at 15,000 ft anywhere in the province in order to track you. 

 You can talk to ATC in the Center pretty much anywhere in the province above 4-5k because of the PAL's, but due to terrain, they won't see you on radar until 15000 only in a few small areas and remote areas that don't see much traffic low level as it is.

17 hours ago, Dave_YVR said:

 You can talk to ATC in the Center pretty much anywhere in the province above 4-5k because of the PAL's, but due to terrain, they won't see you on radar until 15000 only in a few small areas and remote areas that don't see much traffic low level as it is.

OK cool - good to know. But is it not the case that most, if not all of the VATSIM-VATCAN VFR flight following for the province is handled out of CZVR? That's certainly the impression I got and I figured that was the case because FSS's such as the BC regional station at Kamloops aren't simulated in FSX. Maybe it's a human resource thing though, in that it's just not realistic for VATCAN to staff more than Vancouve center?

 As far as I know, VFR flight following online in the BC area isn't really a thing. You can request it, but most of those guys probably wouldn't know what to provide or how it's really done out in the real world. IRL most radar flight following IS done through the Center, I'm not sure what you would be expecting from online FSS. Staffing wise online you are lucky to get a CTR guy let alone an APP or TWR at the same time for CZVR. There was a time when it was common to get 6 or more controllers for CZVR but that was ages ago, not sure what it's like now.