I'll second REW's suggestion of using crystal controlled scanners. They are a dime a dozen at swap meets and garage sales. My main one is left over from 30 years ago when I was a news man. Only one crystal in it, set in the power on channel, all other channels locked out. Never failed me in several years. I've had several WX radios (I practially collect them) and none meet all my requirements for an EAS system of always staying on, responding to everything, being easy to interface and being sensitive enough to work. The scanners usually have built in antenna jacks, no decoders to worry about (why bother since your endec does that), low impedance speaker level output that's relatiely easy to distribute and the price can't be beat even if you have to spend 5 or 10 bucks for the crystal. I'd avoid the synthesized ones, just to KISS. Mine does run on a UPS but it worked for a long time before I put it there as an after thought. If you use a conventional weather radio some idiot will put it in alert mode and the Endec will miss the tones.
Bill C,, Co-Chair, Southern NV Operational area.