[n86121]

I think the real question now is,

"Do enough aircraft now have ADS-B out
to become reliably and directly visible to other aircraft,
in areas of no ADS-B ground stations?"

My Ryan is sick, and I am wrestling weather or not to fix it for $4k
(About what it cost to install, BTW).

9900 BX TCAS (AVIDYNE)

For years I have had a 9900BX which interrogates ALL 1090 traffic within 30 miles,
and a pleasant little voice that tells me if anything is interesting.

It is like having built-in radar flight following.

The interrogating 9900BX (or re-labelled Avidyne) sees EVERYTHING that emits 1090Mhz,
Mode S AND Mode C.

NGT9000

I understand the NGT9000 has a golden-screwdriver unlock that interrogates like the TCAS. When I checked into it, it also requires a $3k Skywatch antenna. Open to updates~!

==

ADS MOOSH

The evolution of these programs has created a mish mash.
While you get a lot of data, you really don't know what's missing.
It is a cloud of visible and missing targets.

Go back to elementary school Venn diagrams. (Wild top-of-head approximations here):

98% of airliners have BASIC 1090 Mode S transponders 1090 MHz
Invisible to 978Mhz UAT
Invisible to 'dual mode' 1090 listening devices (because no position info in C or S)

Only visible in ADSB world if
Ground based radar observes and ADSB ground station sends back out

2% of airliners have Mode S extended squitter ADSB 1090 Mhz
Invisible to 978Mhz UAT
Visible to 'dual mode' 1090 (Because extended HAS position info)

Airliners fly IFR so for the most part ARE visible to radar
so WILL be sent out from ground ADS stations, if YOU are within station range.

Otherwise one can pass off your nose and ALL our black boxes will never see it,
EXCEPT an interrogating Ryan or NGT 9000.

70% of GA aircraft have ADS-B out UAT 978 Mhz
Invisible to TCAS 1090 MHz
Visible to RADAR if within radar coverage
Visible to UAT IN 978 MHz

5% of GA aircraft have ADS-B out Mode S extended 1090 Mhz
Invisible to UAT in, unless observed and relayed by ground station

===

Mode S = aircraft ID, Altitude, squawk = no position
Mode C = altitude, squawk
Mode S Ext= aircraft, altitude, squawk & ads-B = position
UAT OUT= 978 Mhz = blind to the entire 1090 world w/o nearby ADS ground station
UAT IN = 978 Mhz = blind to the entire 1090 world w/o nearby ADS ground station
Dual Mode = Listens on 978 UAT and 1090 (but only sees Mode S extended w position)

Airlines have been exempted from ADS-B Mode S extended squitter,
so don't hold your breath to seeing them on your UAT IN anytime soon.

==

Funding for ADS B was justified by FAA (and the USAF)
as a way to get the private sector to buy the replacement
for areas of dying FAA radars. So it has lots of holes.
And likely to stay that way.

USAF is trying to get control of the $15b from the spectrum sale of 5G to put in more radars
Which might, or might not happen.
So CONUS coverage might get better IF USAF feeds that data to FAA for distribution over ground stations.

So down low, or out of ground-station coverage, TCAS the only way to go.
There may be lots of traffic, but you may be missing a lot of it.

What a mess!