Railfan Technology > Uniden BC125AT question

Being a newbie with this scanner, I have encountered a problem that I cannot explain. When scanning my "Bank 1" where all my channels are, the railroad frequencies come in fine. When it hits a certain frequency for county alerts, that message will come through fine and then the scanner shuts off. Based on this information can someone explain why this is happening? Could it be a malfunction of the scanner or frequency issues. Thanks for any information.

It sounds like a malfunction to me.  One thing that you might check is the battery.  If the batteries are weak or have bad cells, it may scan, but may "choke" when it has to power the speaker, especially for more than a few seconds.  That may send the radio to a low battery voltage condition and it could automatically shut off.  On my BC-125AT, I have the radio set to give me an audible "low battery" warning, but even that warning is not far in advance of the radio powering itself off.  One other battery thing on the BC-125AT--the battery terminals in the radio can be kind of flimsy and, particularly if one changes batteries often, the terminals can sometimes fail to make good contact with a cell.  I physically check those terminals every so often.  

Agree it could be a weak battery that coincidentally shows up during the extended message from one particular channel, but we would need more info about the battery situation.

An easy way to challenge that idea is to go to a continuous broadcast channel, my favorite it the NWS weather service. If the battery can maintain the load for a few minutes it would exclude the battery. Perhaps one of the batteries is weak or some other issue, the batteries are in series so if one battery fails the radio shuts off pretty quick.

Another idea would be to use a different power source, not sure what the options on that would be.

I've had a similar problem with portable scanners that have slide-in battery contacts.  The metal battery contacts slide into the plastic guides on the radio and contact the built-in terminals leading to the radio chassis.
My MVT-7100 went dead one day, and a tap on the back brought it back.
Agree when batteries are low it doesn't take much extra load, even if momentary, to cause a scanner to shut off.
Even my 40-year old HX-1000 will occasionally do that, then it's time for a charge.