Hi,
Just some additional info you might enjoy.
Those FAA 978 and 1090 rebroadcast towers are sometimes but not always at airports. The one near me about 3 miles away broadcasts on both 1090 and 978. It looks like the typical cell/mobile phone communications tower, and I’m sure they are just leasing space on the tower.
Here is an older, and possibly slightly outdated site with a good list of those sites.
http://towers.stratux.me/
Based on your location near KFDK, Frederick Muni, MD, this is the likely one you are receiving.
Google Maps link to site at KFDK: (Use sat view and StreetView)
39.41148, -77.37093
http://maps.google.com/?q=39.41148,-77.37093
If you use Google Streetview, you can see a great view of the site including:
-Electric transformer outside the fence.
-Electrical boxes inside for AC and backup power.
-Big box at back for electronics and network connections.
-Propane tank in front and backup generator further back.
-Multiple 978 and 1090, and probably others on the tower.
These towers are not especially tall, because they are designed to receive and transmit to aircraft, and not especially ground sites like us. I just barely receive the site 3 miles from my home.
TIS-B and ADS-R is rebroadcast on both 978 and 1090.
The 978 broadcasts can include 1090 traffic, and also 1090 traffic that is mode-a/c only. These aircraft will be identified with a pseudo hex code. Locally, mine start with 290xxx, but that varies by area.
The 1090 broadcasts can include 978 traffic, and also the 1090 mode-a/c only aircraft.
Both can include military 1090 mode-s and even 1090 ads-b that might otherwise be blocked. Some of those “real” military aircraft with real, valid mode-s codes will sometimes be identified with those pseudo hex codes like 2990xxx in my area.
The positions broadcast for the mode-a/c only aircraft are based on FAA radar tracks.
978 broadcasts also include weather and test data like notams which can be decoded. The towers also broadcast their ID and location, which can also be decoded with special software.
Occasionally, you will even see a “double track” when an aircraft is received locally by ads-b, and then you also see a TIS-B FAA radar track for the same aircraft. That sometimes happens when the two tracks have not yet been correlated by the FAA system. The ADS-B track will be perfect, and the FAA radar track will wander a bit since it is based on radar, not GPS.
I did not see any pseudo hex codes in your image, so those are all aircraft with valid mode-s codes.
Regards,
-Dan
