SDR CTF: Air Band

Between Commercial FM and the 2-Meter Amateur band is the air band used by commercial aviation for air traffic control and navigation. I picked up a sectional aeronautical chart which has helpful information on what channels are used by which airfield and the location of radio navigation devices. In areas where there is not an identified channel on the chart, you may find traffic on 121.5 (the emergency channel,) 122.2, 234.0 and 255.4 MHz. Also of note, on one of these charts you can find the highest points in the area either geographically, or towers or buildings. This information might be helpful for other communications purposes.

Looking at the nearest major airport to me, Port Columbus International (CMH), it's pretty busy with lots of notes. I can pick out:

• CT (control tower) 132.7 MHz AM
• ATIS (automatic terminal information system) 124.6 MHz AM if you want a nice voice-to-text experience

There is also a communications box identifying itself as "Columbus RCO" noting that voice is out of Dayton on 122.2 and 122.3

Note that these are AM signals.

Next Steps

There's more than voice traffic, most aircraft is sending transponder data via ADS-B and some are sending ACARS.

We also mentioned radio navigation beacons.