Found an old reference saying it is for Goshen, IN. I've definitely heard traffic on the air side of it, but not sure about ground TX.
Thanks for the tip, appreciate it.
Programmed the other Goshen, IN RCAG RR DB freqs into RX:
127.550
128.800
307.175
314.000
but didn't hear anything on these with activity on 263.1.
Another strategy would be to search/scan VHF ZAU RCAG freqs for the same controller voice & if found, assume simulcasting from same RCAG location. Didn't have the opportunity to start this though.
Later on, about 10PM Central, UHF ZAU RCAGs at Dubuque 327.15 & Horicon 269.075 started breaking squelch on RX & were readable. There may have been some slight WX-related propagation enhancement occurring...passing front, temperature inversion, etc.
Gonna try a cross post over on Groups.io/Militaryscan, no hits there for "263.1".