A question about 8.33 KHz comm spacing in P3d5 (resolved)

[jabloomf1230 2,445]

Myself and at least one other user have run across this issue with the RXP GTN 750 in P3d5. 

The Garmin GTN 750 trainer works perfectly offline. When tuned to any 8.33 KHz frequency in that mode, the display is correct. However at the stock EGKA Shoreham, In 8.33 KHz mode, the RXP gauge display always changes the Shoreham Tower frequency of 125.405 to 125.400. I'm not sure how this is even possible since the RXP gauge is based on the Garmin trainer. I thought that it could have something to do with also having the legacy radios also active, which of course can't display 8.33 KHZ frequencies correctly. I changed my panel configuration to eliminate the legacy radios, but that did not help. When flying the P3d5 default C-130 out of EGKA (!), which has native 8.33 KHz capabilities, the ATC works perfectly. The gauge is installed in the RealAir Turbine Duke and works perfectly in the normal comm mode.  It's also possible that this one frequency (125.405) is broken, as I haven't spent time trying to check every 8.33 KHz frequency. Thanks in advance.

 

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[RXP 2,338]

Hi,

The only reason the GTN can change frequency automatically is because the simulator frequency is changing and it is syncing with it. The reason the simulator frequency is changing then is unknown to me, but I'm looking at this EGKA info which differs:

https://skyvector.com/airport/EGKA/Shoreham-Airport

https://www.vatsim.uk/airports/EGKA

https://garfnet.org.uk/cms/tables/radio-frequencies/aircraft-frequencies-uk-europe/

They are listing 125.40 (not 125.405). Is the GTN showing 125.405 in its database?

Edited July 17, 2020 by RXP

[jabloomf1230 2,445]

The GTN database shows 125.405, but the stock P3d5 EGKA shows 125.40.

Update: I also checked the latest Navigraph AIRAC and it shows 125.40 also, as does fsaerodata. Maybe the issue is with the trainer.

Edited July 17, 2020 by jabloomf1230

[RXP 2,338]

The trainer DB is probably wrong in this case, but maybe not:

If there is any code not working with 8.33Khz in P3D5 and 'rounding' these to 25Khz, the 125.405 will get rounded to 125.40 into P3D5, which then will sync back as 125.400 into the GTN.

[jabloomf1230 2,445]

No the Garmin GTN trainer db is correct. I just checked the official UK eAIS and the Shoreham tower is definitely 125.405:

https://www.aurora.nats.co.uk/htmlAIP/Publications/2020-07-16-AIRAC/html/index-en-GB.html

That might be password protected, so here's a screen shot:

 

[jabloomf1230 2,445]

I don't suggest that you spend  too much time on this, as it doesn't seem to be easily correctable. It seems like the real world EGKA and a few of the recent 3rd party versions have the correct tower frequency. I'm going to check with Navigraph via an email, to see what the story is with their database. These are the only invalid comm frequency fractions:

.020, .045, .070, .095

Every other comm frequency that ends in a 0 or a 5 is valid.

 

[RXP 2,338]

Ok, just keep us posted as this might help others!

PS: So much so for those claiming the GTN DB is outdated and unusable, vs the latest 3rd party DB you can update the simulator with. This goes down to: there can be errors in any DB but most DB items don't change much over time.

[jabloomf1230 2,445]

I figured it out. The story is quite convoluted (and I'll spare you all the details), but the RXP gauge is working correctly, so you can mark this as solved (somewhat). It all stems from LM not relying on official government information for airport navigation data, but rather what's posted online in those flightsim navigation websites, like SkyVector, etc.. LM's stock airport in P3d5 has the tower frequency as 125.400 and this value has translated across every add-on, including anything that uses Navigraph. Navigraph support told me that they used the 125.400 because LM used it and doing otherwise would cause an inconsistency in P3d5. Any 3rd party ATC app like VOXATC will correct the user if an incorrect frequency is entered. So if the user enters 125.405 it just switches the display back to 125.400. 

Ah the joys of a flightsim with open architecture...

[RXP 2,338]

10 minutes ago, jabloomf1230 said:

but the RXP gauge is working correctly

This is all good to me 🙂 

Thank you for your astute research on this issue, it will certainly help others in the future wondering about this.