Hi,
I hope I`m in the right category for my question:
As the title says, I’m wondering what the average or typical range for COM radio frequencies of bigger airport is.
And if that range is somehow realistic simulated in the sim.
For example yesterday, I loaded my A320 FCU with an Simbrief flightplan, but on the way to my destination I became quite sure that due to changing wind direction the runway that Simbrief suggested was not right any more.
So I dialed in the COM radio frequency of the destination airport, expecting a different approach instruction.
But at a distance of about 70NM range, I still had no COM connection (airport also didn’t show up in the ATC options yet). But at that distance I was already way beyond my TOD for the original planed approach.
And is that a realistic range?
I really don’t know how it is in RL.
It just seems to be a quite short range under some circumstances like the one I described above.
In RL, if you are one the ground at an airport, you will be luck to hear Com radio from another airport much more than 10 miles away. If you do hear anything, you are more likely to hear the Airport ATC, transmittmg from a mast some height above ground, than the planes at ground level.,
Think of Aviation Band radio frequencies as being “line of sight”.
I used to be a radio fault find engineer for about 12 years, working on Military, and emergency services radios. VHF frequencies have better range, but aren’t good at punching through solid objects like hillls, buildings, and the like. UHF is kind of reverse, and is much better at getting through more solid objects but doesn’t have the same range.
The radios I worked on were hand helds, and mobiles, so all at ground level, and not huge 100ft masts!
10 miles is probably about right. The best we ever managed, I think for a portable, was around 7 miles, and that was an E-band radio, at around 80MHz. Very long antennas on those.
Sitting on the ground, you can often hear aircraft talking to ATC, when they are flying high, and are 100+ miles away, but you will not hear the ground base ATC talking back to them.
The complication comes in with terrain, and what is between the transmitter & receiver, and their relative heights BUT in theory, all of this information is available in the sim, so that realistic Radio ranges, “Could” be simulated, rather than an arbitrary fixed range.
I’ve definitely had crackly ATC audio when in mountainous areas, and seen my reception of VOR’s, and NDB’s drop out as well, so I’m reasonably sure it simulates terrain affecting reception.
In my fading memory I seem to recall in real life speaking with Cape Town (FACT) all the way to the Sutherland (FASL) reporting point while flying in South Africa many moons ago. I just checked with my sister who still flies there and she confirmed on a recent flight she was speaking with Cape Town beyond Sutherland from normal C172 VFR altitude of around 7,500ft on that route. That is around 135nm FWIW.
Much further than that, things used to become iffy before you got within range of the repeater station at the Orange River. So beyond that I regularly asked South African Airways aircraft to relay position reports to Cape Town for me. Lot less aircraft in those days: airline pilots were quite happy to provide the relay because the sky was quite empty and it helped pass the time I suppose…
I believe if you place yourself at the other side of a mountain ridge to an Airport, you will hear them just as well as if the mountain was not there – or monitor the nav radio signal strength, that while changing with range, cares little about what is between you and the other radio station.
Nav radio is either ON/OFF as your exceed a given range limit , with no introduction of noise on a weak signal.. while at least COM radios seem to introduce some interference as the radio range reaches its limits. (if that option is selected )
If that’s right I wonder what was causing my NAV drop outs in that case. I could definitely see the signal being intermittently lost as I was flying low level through mountainous areas in BC.
In one case I was flying roughly towards an NDB, perhaps at 10 o’clock.
Got me interested now – as last time I check (some time ago), the range simulation did not appear to be that complex.
Its a question I raided on the SDK Dev forum about a year ago, and nobody at that time seemed to have any interest in even discussing it, so I assume it was not on the Asobo roadmap (at that time)
In flight you would not tune in tower or ground frequencies from far out for your arrival planning, but ATIS or AWOS.
As others have said the range depends on your elevation, that of the airport and that of terrain that lies in between.
In the US you had one more ace which is called FSS flight service stations. You can call them on dedicated frequencies, sometimes even using NAV radios as relay stations, to get updated Wx information in flight. Something that of course is now less frequently done, with inflight information through various other sources.
Based on your description however you were on an IFR flight under ATC control. In that case the instructions would come from ATC when to leave your cruise altitude and which approach to expect etc.
Though we all know that the built in ATC makes a royal mess out of that on a regular basis😉
50-60nm however were not unusual even flying around the pacific southwest to be able to pick up ATIS or AWOS. The actual com frequencies usually are turned down some, so that you do not interfere with other airports using the same frequencies.
