Peter wrote:
But I know nothing about CPDLC modulation etc.
The current implementation, VDL mode 2, uses DPSK at 31.5 kbps raw physical bit rate.
The GTN750 employs FPGAs, at least it says something about configuring them on start-up. So it might well be possible to implement it as a SW update. This is only an unfounded guess, however, I have no idea about the design details.
A few problems, technically I am sure the radio side is simple. But you need to pay for a provider to use datalink which means it will never make sense.
Also, in order to be used for CPDLC rather than other service like weather and DCL clearances it needs to be approved by Eurocontrol.
What does the CPDLC interface look like at the ground end? Is it some sort of IP (or even AFTN-addressed) gateway? Presumably the physical appearance (on the ATCO’s desk) is a keypad and a display?
Sure one has to pay for the VHF or satcom data link and with airlines being the principal customers, one can be sure somebody will be milking that part of it.
Similar discussion surely is ACARS – another VHF or satcom data link but this time going to the ops department so no need to be ATC compatible. One could easily implement that on the back of the Golze ADL setup which already does messaging, with a gateway for SMS. I am sure Sebastian could easily do a gateway to telegram, email, or a messaging (“chat”) user interface on a web page etc.
Controller–pilot data link communications V2: US PDC & D-ATIS
I think this has much more potential for GA than CPDLC, if only Eurocontrol and all the NATS could get their act together (dream dream):
US Mobile PDC & D-ATIS
I’m green with envy. This would be soooo useful for non-towered airfields in G airspace in Europe. 
But one can fantasize, eh?
Yes it works brilliantly in the US. But only out of larger airports. D-ATIS also exists in Europe but no GA source ie FF provide them. FF provides D-ATIS in the US.
ATIS by text seems to me gimmicky when I can open Foreflight on my phone and get a METAR for any airport (ATC controlled or not, as long as it has AWOS or ATIS) by touching its location on the chart with my thumb.
you need to pay for a provider to use datalink
Interesting, I didn’t know that. Out of curiosity, how does it work? Can you choose from different providers and do you have a SIM card in that box like in a cell phone?
Silvaire wrote:
ATIS by text seems to me gimmicky when I can open Foreflight on my phone and get a METAR for any airport (ATC controlled or not, as long as it has AWOS or ATIS) by touching its location on the chart with my thumb.
Yes, but that doesn’t give you the full ATIS and, importantly, not the letter (Alpha, Golf, whatever) or the approach in use. FF here have it, but unfortunately only with the top-of-the-line subscription and then only for the bigger airports. I really hope the FAA roll that out to all towered airports. Having to listen to the ATIS while also talking to ATC (especially in the L.A. basin, where ATC comms are pretty much a constant rapid-fire verbal stream) is a pain.
Isn’t that data over the GSM network? If you have that, there is no issue; everything is free, basically…
