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Railfan Technology > Why knowing AAR Radio Channel Nos. is important

Date: 05/20/23 14:36
Why knowing AAR Radio Channel Nos. is important
Author: WW

Here is a dirty little secret that still lurks unspoken among most of the railfan community:  About the only people who refer to a railroad radio channel by its frequency are a very few railroad radio technicians and most railfans.  Almost everyone else in and around the railroad industry refers to railroad radio channels by their AAR Channel Number.  Most railroaders don't know and don't care what the frequency is of the railroad radio channel that they are using.  So, why is this important?  Because, when you are in the field and a train crewperson says, for example, "we're going to Channel 023 023," you don't want to be fumbling around trying to figure out what the radio frequency of Channel 023 023 is (it's 160.4550 mHz, by the way).

So, here is a quick intro, for those not familiar with the AAR Channel No. system.  There are several sources out there for the AAR Channel numbering scheme, here is the one that I use:  https://www.radioreference.com/db/aid/7747 .

Some history:  For decades, the U.S. and Canadian railroads used 97 AAR-designated VHF radio Channels, designated AAR Channels 01-97.   The full AAR Channel No. was a pair of two-digit numbers,the first being the transmit channel of the radio, the second being the receive channel of the radio.  So, in our example, a radio tuned to 160.4550 mHz for both transmit and receive would have been Channel 23 23.  Many railroad employees still use those numbers, though narrow-banding in 2013 caused the railroads to use pairs of three-digit number to designate the channel.  This same frequency (just narrow-band instead of the "vanquished" wide band) has an AAR Channel No. of 023 023. Note in the AAR Channel list that there are now analog "splinter channels" available, numbered 107-198. All AAR Channels from 001-198 are analog radio channels.  With the adoption of the NXDN digital platform by the railroads in 2013 (though few railroads are using NXDN now, even though nearly all Class I railroads have been purchasing NXDN-capable radios since about 2012), those digital channels were assigned there own AAR Channel Numbers.  Note that NXDN channels use the same frequencies as analog channels, but carry different AAR Channel Nos.  In our example, the 160.4550 mHz frequency being used for NXDN digital communications would have an AAR Channel No. of 339 339.

In cases, where a railroad would be using a different frequency for a transmit channel from the receive channel--say, when accessing a repeater--this would be reflected in the AAR Channel No.  For example, let's say that the railroad was using the frequency of 161.460 mHz (AAR Channel No. 090) for transmit and our 160.4550 mHz (AAR 023) channel example for receive, the AAR Channel No. for that combination would be 090 023.

So, how to use these numbers effectively for using your radio for railfanning:  My suggestion is buying a radio that supports "alpha tagging" of frequencies entered into the radio.  Many amateur radios do this, as do  most all commercial radios, and scanners such as the ubiquitous Uniden Bearcat BC-125AT.  Many amateur radios and scanners also allow the user to toggle the display between displaying the frequency or the alpha tag, in this case, the alpha tag being the AAR Channel No.  With the AAR Channel No. alpha tags programmed into the radio, the railfan will be able to easily select that AAR being used by train crews, etc.

One final note, a lot of railfan websites and publications continue to publish ONLY the railroad frequency and not the AAR Channel No. in posts and publications--Trains Magazine is a major offender in this regard, but by no means the only one.  They need to publish both in their articles and postings.  I even spoke at length about this to the late Jim Wrinn when he wast still the editor at Trains Magazine.  I plant to "remind" them about this oversight again soon.

EDIT:  The original link to the AAR Channel Plan has a error in the splinter channels designations; the new link inserted in the edit is correct.

Edited 1 time(s). Last edit at 05/21/23 10:01 by WW.

Date: 05/21/23 08:36
Re: Why knowing AAR Radio Channel Nos. is important
Author: ironmtn

You make a very good point. Through the years, I've known a number of railfan friends who programmed in the AAR frequencies. Before radios with alphanumeric tagging, they were careful to do so in numeric order by the AAR channel number, so that they could switch to that channel easily, even without a visual display. Particularly when they heard a channel change transmission such as you mentioned, or saw a sign along the track indicating a channel number change.

Some only kept those AAR channels, and some never even used other channel banks on their radios (once those became available) to program in other AAR channel groupings or frequencies for their favorite or more frequently monitored railroads. And they made it work just fine.

I never took that approach. Once I finally got a radio with frequency banks, I programmed in groups of frequencies for railroads by geographic areas. That approach worked as well - mostly. But, when I'd hear one of those channel change messages, or saw a sign along the track indicating it, my monitoring was sometimes silenced because the channel changed to was a secondary frequency that I hadn't programmed in that geographical group. Sometimes because I just thought it wasn't important to have, and sometimes because other frequencies I wanted in that geographical group had filled that bank on the radio. And yes, I was left stumbling to find out what the frequency was for that AAR channel, and to program it into the radio manually in the field. Not a huge problem, but it took time, and was a distraction from the action. And I probably missed a few shots with the camera while I was doing that.

I like the geographical grouping pattern still, and find it useful. BUT - it should not be the sole organizational principle. I should ALSO have maintained all of the AAR frequencies, in numerical order, and (once I had a radio with a digital display), also programmed in the AAR channel name for the alphanumeric display. With both schemes, I could use either. And if I was monitoring using a geographically-oriented channel bank, and I heard either a AAR channel change transmission or saw a sign  along the ROW for one, I could quickly and easily enable the bank with all of the AAR channels, and easily select the channel number indicated.

Not only was I not wise enough to realize this when I got my current radio, a Uniden Bearcat BC-125AT, but I stupidly compounded my mistake. When I bought the radio, all of the AAR frequencies were pre-programmed by Uniden into Bank 1 out of the box. I'm not sure if that's still the case, but it was then. All I had to do was to add the AAR channel name tags (if they were not already programmed in by Uniden - I don't remember).

But I thought - stupidly - that I had a better idea. I wanted Bank 1 to be my "trip priority" bank, which would have all of the frequencies for a certain pre-planned trip (like chasing a steam excursion) in that bank. No need to select them out of other banks or groups, or to use the "real estate" of another bank. They would all be easily accessible there - just open up that bank. And all of my other geographically-oriented banks / groups would still be there, available for use if I took the proverbial "long way home" from the special, designated trip. And available for other trips.

And with that said, yes, you may be able to guess the rest. To open up Bank 1 for that purpose, I deleted every one of those AAR frequencies. And some other pre-programmed public safety frequencies too. I got my Bank 1 Trip Priority Group alright. But now - if I wanted all of the AAR Channels again to easily switch to one by AAR Channel number, I would have to reprogram them all to make such a selection when needed. Like when I heard a train say, "switch to channel 20". Or whatever.

It was one of the dumbest things I have ever done.

Time has made the mistake worse, I really like the radio, and WW has acknowledged it's okay. It works very well for me, and I'm just not in the market for or desirous of a more sophisticated, better quality unit. But the jack on the side of the radio that Uniden made to do double duty for a recharging port and a programming cable no longer works and needs repairs. It is just not a high quality jack, and frequent use with the recharger early in the radio's life with me has worn that connector, or a wiring contact. I always found the charger to be very slow, and when that jack started acting up, I abandoned use of the jack for recharging and went to removable rechargable, or even regular AA batteries, which have worked fine. Yes, as WW once warned, the contacts in the battery compartment are not too sturdy, so I take batteries out and put them back in with care. So far though, so good on that score.

But even without recharging use, the jack has worn out, and no longer communicates with the cable for software programming either. Getting the jack fixed has proven to be challenging. No radio shop in my area wants to do the work, and a shop I found online which was willing to do so now no longer does. I can get by fine for power using removable batteries. But now if I want all of those AAR channels again - as I have, many times, along with my other geographically-oriented channel banks - I will have to manually program them all back in, one by one, using the radio's controls. Which are fine for adding a frequency now and then, But for adding all of the AAR channels it will be an arduous piece of work. Yup, you guessed it, I've never done it.

So, a word to the wise.

1) If your radio comes with all of the AAR channels / frequencies pre-programmed, do NOT delete them. If the AAR Channel numbers were not pre-programmed also for the alphanumeric display, add those alphanumeric codes as you can and time permits. And if you want to ALSO use another organizational schema, such as the geographical groupings I use, then ALSO program those groups separately in OTHER banks.

2) Likewise if your radio doesn't come pre-programmed with the AAR channels / frequencies, then program them all into one or two banks. You will want them, and accessible in that scheme.  And then separately program in your other groupings into other banks. But by all means have all of the AAR Channels available, and easily selectable by AAR Channel number as the organizational scheme, as needed.

You can use the AAR Channels as such as your primary organizational schema, as many railfans do. Or you can use them in addition to other organizational schemes in other banks. But make it a HAVE BOTH situation - and NOT an either-or situation.

You will thank yourself many, many times for the wisdom (which I failed to have) of doing so.

And sincere thanks to WW for his oh-so-wise advice in the original post for this thread. It is advice that is oh-so-true. And don't I know it. From hard-won experience.


Edited 1 time(s). Last edit at 05/21/23 08:42 by ironmtn.

Date: 05/21/23 09:58
Re: Why knowing AAR Radio Channel Nos. is important
Author: WW

On my BC-125AT,. the railroad "Service Search" must live in the firmware of the radio, not in the regular 10 memory banks.  When it stops on a channel in Railroad Service Search it displays what looks like an AAR Receive/Transmit block (e.g., 118R/166T), but with the Receive channel first, opposite of the AAR naming convention of Transmit Channel/Receive Channel. The first number correctly refers to the correct AAR Channel No. for the frequency; I have no idea what the second no. refers to. I see no way to access the Service Search channels to modify them in the BC-125AT programming software. 

As to the memory banks, here is how I have my BC-125AT set up.  The first 6 channels of the AAR Channel Plan (AAR Channel Nos. 001-006) are for Canadian use only.  So, in my radio I use the first 6 channel slots in Bank 1 instead for the 6 UHF train telemetry channels.  Then I enter the AAR channels as follows:
Bank 1 - Scanner channels 7-50 AAR Channels 007-050
Bank 2 - Scanner channels 51-97 AAR Channels 051-097
Bank 3 - Scanner channels 107-150 AAR Channels 107-150
Bank 4 - Scanner channels 151-197 AAR Channels 151-197

This leaves the remainder of the banks (5-10) available for other entries, and leaves Banks 1-4 for railroad channel use, with the Scanner channel no. being the same as the AAR Channel No.  

Edited 2 time(s). Last edit at 05/21/23 10:03 by WW.

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