Save your money and don’t buy a scanner Whistler or Uniden; neither will properly decode NXDN node do they properly respect wildcard RAN, NAC, etc. If you’re serious about rail communications, either get a Icom R30 or a real AAR radio such as an Icom IC-F3161, F3261 or F3400 loaded with AAR firmware.
I second this, but the AAR firmware isn't necessary. I use an F3161DS without the AAR firmware and it's great. The only pain is manually entering all of the AAR channels by hand the first time around, but it can be done and transmitting can be disabled. The AAR firmware has keypad entry of channels (it's only available on the full keypad versions to my knowledge) which is great and all but can lead to accidental transmissions and that's a big no-no. You can also turn keypad entry off if you REALLY want an AAR firmware radio. All things said and done, if you find a good deal, you can get a used Icom radio with all of the fixings for programming it up to your liking for about as much or less than a Whistler TRX-1, which is just "okay." I also own a TRX-1, and would NEVER bring it as my main trackside radio unless I can't bring my Icom. The audio is super quiet and would not be heard over the sound of trains going by when trackside. Mind you, the Icom is also relatively quiet so a speaker mic or earpiece would be even better, especially when riding so you don't raise the eyebrows of fellow passengers or employees.
TL,DR: Get an Icom F3161 or F3261 and program it with AAR channels RX only and you'll be a happy railfan.
Source: A happy railfan and licensed amateur radio operator who has done the above ^-^