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FSX Com frequencies


I am attempting to create an AFD file using a com frequency of 129.92 and get the following error in the FSX BGLComp:

Parsing document: P:\afx.xml

INTERNAL COMPILER ERROR: #C2424: COM FREQUENCY can be 118.000 to 136.992Mhz in 0.0083Mhz steps!
INTERNAL COMPILER ERROR: #C2031: Failed element parse <Com>
INTERNAL COMPILER ERROR: #C2032: XML Parse Error! Element tree follows:

ERROR: version = 9.0
ERROR: <Airport
ERROR: ident = EGHF
ERROR: region =
ERROR: country = United Kingdom
ERROR: state =
ERROR: city = Lee on Solent
ERROR: name = Lee on Solent
ERROR: lat = N50 48.94001
ERROR: lon = W001 12.40001
ERROR: alt = 9.85M
ERROR: magvar = 3.00
ERROR: frequency = 129.920
ERROR: name = LEE
INTERNAL COMPILER ERROR: #C2607: Compilation errors detected, compilation failed!

So I changed the frequency to 129.9188 which, according to my calculation is divisible by 0.0083 when 118.0 is subtracted and it still fails.

I had previously compiled an xml file containing com=119.6 which is patently not divisible by 0.0083 and this compiles correctly :confused:

Does anyone have an explanation?

Hello George.
Surprisingly it seems that the compiler is up-to-date with this new standard but the equipments of FSX are not...
The 8.33 KHz separation (implemented some months ago) would give in this frequency area: 129.900 129.9083 129.9166 129.9250 129.9333 129.9416 129.9500 129.9583etc...


EDIT :.I have modify one XML just to see and it appears that when a 8.33 khz frequency is available FSX automatically adjusts step to 8.33khz. It's possible to go back to the 25Khz by selecting another frequency. In testing this setting with a ground frequeny, I noticed that this frequency was remaining silent and that no AIs were departing. Shortly after the landing ones, when vacating runways, stopped at Hold short but didn't contact ground. Obviously something is going wrong with this setting. Back to 25khz!

Last edited:
Hi Xavios,

I don't understand your calculation. You say that 129.9 is a valid frequency but, according to the error message:

COM FREQUENCY can be 118.000 to 136.992Mhz in 0.0083Mhz steps.


129.9 - 118 = 11.9

11.9 is not divisible by 0.0083 (nor even by 0.00833)

129.900 is a classical frequency with the 25khz step. In the old system the step was 025 (25khz step) after the decimal ie 129.900,129.9250khz,9500,9750... Inside each 25khz it has been created 3 extra frequencies by dividing this 25 by 3 and so to obtain a 8.33 khz separation. It's then rounded to the last three digits (well looks like). You are right the frequencies I gave were not rounded.
In your proposed frequency129.920, 5khz are missing and the initial 25khz step is not available.
Here as some frequencies in use in the French airspace (8.33khz airspace upper region>FL195)
Hope it helps
The Bglc message was not incorrect because to be a good 8.33, the frequency must be a valid 25khz one's initially. I should say, no 25 and therefore no 8.33. If you put 129.925 it will be compiled without any problem. The compiler just makes a routine check.

OK, the error message should state the the steps are 25/3 Mhz and not rounded it to 0.0083.

All of this is academic in any case, as FS ATC only supports 0.25 KHz steps... ;)
I also think it was some kind of academic until I find that FS(X) supports this step in a certain way, as I said in the"edit" of my first post. I think it would not be a good idea to create one though, because only the user aircraft seems to be able to contact it.