01 159.570 02 159.810 03 159.930 04 160.050 05 160.185 06 160.200 07 160.215 08 160.230 09 160.245 10 160.260 11 160.275 12 160.290 13 160.305 14 160.320 15 160.335 16 160.350 17 160.365 18 160.380 19 160.395 20 160.410 21 160.425 22 160.440 23 160.455 24 160.470 25 160.485 26 160.500 27 160.515 28 160.530 29 160.545 30 160.560 31 160.575 32 160.590 33 160.605 34 160.620 35 160.635 36 160.650 37 160.665 38 160.680 39 160.695 40 160.710 41 160.725 42 160.740 43 160.755 44 160.770 45 160.785 46 160.800 47 160.815 48 160.830 49 160.845 50 160.860 51 160.875 52 160.890 53 160.905 54 160.920 55 160.935 56 160.950 57 160.965 58 160.980 59 160.995 60 161.010 61 161.025 62 161.040 63 161.055 64 161.070 65 161.085 66 161.100 67 161.115 68 161.130 69 161.145 70 161.160 71 161.175 72 161.190 73 161.205 74 161.220 75 161.235 76 161.250 77 161.265 78 161.280 79 161.295 80 161.310 81 161.325 82 161.340 83 161.355 84 161.370 85 161.385 86 161.400 87 161.415 88 161.430 89 161.445 90 161.460 91 161.475 92 161.490 93 161.505 94 161.520 95 161.535 96 161.550 97 161.565
These 97 channels (in MHz) are used by railroads across North America. At one point there was a plan to include additional channels between the existing ones (...072, 172, 073, 173, 074, 174...) but this didn't end up happening.
Many radio scanners have a built-in list of railroad frequencies that scans ARR channels 7 to 197. Because scanning is done by listening to each frequency for a fraction of a second to see if there's anything there, scanning lots of frequencies can result in missed words at the start of a transmission. This delay is reduced or eliminated by programming 1 to 97 into the saved banks and scanning that instead.
You may want to keep a mental list of the AAR number for each railroad in your area as you figure them out. Some railroads use more than one channel: large yards typically have their own (or multiple), the mainline channel may change between divisions or subdivisions, or there may be a different frequency for talking with the dispatcher.
If you hear a series of tones, it's a sign that that channel is used both for road operations and for talking with dispatch. The radio channel functions normally until a button is pressed in the cab, sending a series of tones that start a phone ringing on the dispatcher's desk (and alert others on the frequency to stop talking). When the dispatcher answers, the transmission is broadcast from repeater antennas every few miles along the track to be received by the locomotive. The crew's response is picked up by the antennas and sent to dispatch. You may hear the dispatcher's side of the conversation but not the crew's if the train is far away.