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NDB question

Posted on December 31, 2012 13:18 by henrimarch

I am getting other frequencies for some NDB's.
I have x-plane airac 1208 downloaded in Airac and this is the same as in the x-plane version which I have running
But for example a lookup RNT - RENTON NDB the frequency is 350 Khz in Airtrack.
This frequency set in X-plane is not responding and when I go to the local map and click on this NDB in x-plane the properties shows its frequency is 353 Khz and with this setting X-plane is responding.
Also in FSX the frequency setting of this NDB is 353 Khz.
This confuses me somewhat (this is not the only NDB which frequency isn't the same) as I find it a pity that I can't rely on Airtrack information or do I something wrong (I am a newbie in the flight simulator world but I really love it).

Kind regards,


Posted on December 31, 2012 15:25 by skyfox


It is strange indeed; it seems like a bug; the frequency in the database for NDB is indeed 353 so I don't understand why it is showing up 350. I will look it up and find out what is causing it and fix it.

Really don't know why, this is the first time it was noticed.

Sorry for it and thanks for spotting it,
Will let you know when it is fixed,
joao @ airtrack

Posted on January 2, 2013 22:39 by skyfox

Hi again,

OK after investigating we've found the cause of this problem and it has now been fixed. There were actually two parts of the problem, with two distinct fixes:

1. Some NDB frequencies were incorrectly encoded in the navigation data sets; these included the RNT NDB you mentioned.

In order to get the FIX go to the Navigation Data page, delete any datasets you have locally stored in AirTrack and download them again. The new downloaded data will have the right frequencies.

Since the Navigraph 1006 cycle is built-into the app, this one will not have the corrected frequencies until we release a new version, so as an interim solution I've made a Navigraph Update 1006 cycle available for download which you can also get via the *Navigation Data* page.

This fixes the NDB frequency problem for all lower NDB frequencies in the range 190 to 535khz, so all the US NDBs should now be correctly reported.

2. There were also some problems detected in some upper range NDB frequencies, but these required some changes in the app itself; so they will only be solved once a new AirTrack version is out. We're preparing a new version with this fix which will be sent to Apple as soon as it's ready, but since they also take some time to review it it might take a couple of weeks until a new version is out.

This second problem only concerns upper range NDB frequencies which are not that common and X-Plane itself truncates some of these frequencies.


In the process of fixing this issue we've learned a few things and encountered a couple of X-Plane issues:

1. X-Plane only shows ADF frequencies with 3 digits, but there are some NDBs with frequencies above 1000 khz (e.g. AK ALEKSANDROVKA 1130.00khz) X-Plane will show you these as 130 I believe when they are actually 1130.

2. X-Plane and its data only use integer values for NDB frequencies, so NDBs with fractional frequencies are truncated or rounded to their integer value. For example, the HLN NDB in Norway which has a real-world frequency of 308.50 khz is represented in X-Plane as 308khz.

Consequently you will find different frequencies for these NDBs if you use the X-Plane data or the Navigraph data (which has the fractional parts).

The next version of AirTrack to be released will deal with both these cases and will allow you to use frequencies above 1000khz and fractional frequencies correctly, while keeping compatibility with X-Plane.


Just as a final note, none of these problems exist with ILS or VOR frequencies. So it is only with NDB frequencies. The other frequencies should be correct and do not need a fix.


Once again thanks for spotting it,
happy 2013,
joao @ airtrack

Posted on January 3, 2013 09:00 by henrimarch

Hello Joao,

Thanks for your quick and thorough response.

You also have a happy 2013,

Posted on January 11, 2013 21:20 by skyfox

Hi Piet,

Just a quick message to let you know that AirTrack 3.5 is now out and that it fixes the NDB issues you encountered; you should now have all NDB frequencies displayed correctly.

The new version also supports sub-kilohertz frequencies such as 308.50 and upper frequencies such as 1130khz correctly, even though the simulators might not.

happy flying,

Posted on January 16, 2013 13:10 by henrimarch

Thank you.

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