[Milsurplus] ADS-B

[Robert Nickels]

When my Jan. 2014 QST article "Virtual Radar from a Digital TV Dongle" 
appeared the transition from traditional voice-based to digital "Next 
Gen" aviation communication, navigation, surveillance, and air traffic 
management was just beginning, with a compliance deadline of 2020.     
The future has now arrived!

ADS-B falls under the umbrella of FANS - Future Air Navigation System.  
FANS was developed to improve the safety and efficiency of airplanes 
operating under time-based procedural control to keep aircraft 
separated, and in order to do that you need to have automated systems 
that report the exact position of each aircraft in real time, which is 
where ADS-B (automatic dependent surveillance - broadcast) comes in.     
Another application known as ADS-C (automatic dependent surveillance, 
contract). In this system, an air traffic controller can set up a 
"contract" (software arrangement) with the airplane's navigational 
system, to automatically send a position report on a specified periodic 
basis – every 5 minutes, for example.

The upshot of all this is to transition from voice reports (based on 
inertial position) to automatic digital reports.  That's not an 
unfortunate side-effect, it has been one of the primary goals for 
modernizing the analog radio-based air traffic control system that still 
uses components dating back to the 1940s.    Of all modes of voice used 
today, HF is the least efficient because it involves contacting an HF 
operator who then transcribes the message and sends it to the 
appropriate ATC service provider who sends it to the HF radio operator 
who contacts the airplane.  We all know that the quality of HF 
connections can be poor, leading to repeated messages and opeators can 
also be saturated with requests for communication.  This leads to 
procedures which keep airplanes separated by as much as 100 nmi (190 km) 
laterally, 10 minutes in trail, and 4,000 ft (1,200 m) in altitude. 
These procedures reduce the number of airplanes which can operate in a 
given airspace and Next Gen is aimed at handling increased aircraft 
density and avoiding congestion.

One major HF radio hardware and service provider,  Collins Aerospace, is 
looking at how HF can be a part of the future solution but not 
necessarily in the present (analog) form.  This is the wideband digital 
HF initiative, developed initially for the Air Force that Collins is 
presenting as a complement to the SATCOM-based approach:

https://runwaygirlnetwork.com/2019/01/15/wideband-digital-hf-a-go-for-the-cockpit-says-collins-aerospace/

As Collins says "SATCOM and HF can work together, simultaneously, in a 
complimentary fashion to provide robust and efficient over-the-horizon 
communications."

To the HF and V/UHF listener, the bottom line is yes, as with virtually 
every other form of communications, the future is digital and there will 
be less to hear.

73, Bob W9RAN