[EAS] Alerting options

[Mike McCarthy]

Illinois has their back-bone system operating in the 44Mhz region and it 
requires 25 interleaved transmitters and two independent networks to 
cover the state. Imagine a state like Texas or mountainous California or 
Montana trying to do that. Who will build and maintain the equipment and 
sustain the operating systems? This will not be an inexpensive endeavor 
if it's to be a hardened and durable system to withstand various natural 
and man-made events, yet reach places that need to be reached with as 
few transmitters as possible.

The most robust, albeit slow, means to convey basic text over the widest 
area is a low frequency sub-carrier on big AM stations. It would pass 
maybe only 20 or so characters per minute.  But in the EAS/CAP world, 
both the header and a URL can automatically be passedin near real 
timeand repeated during the duration window. Plus the system can be 
under continuous test.

A research colleague commented with the proper receiver design and 
heavily narrowed IF, the signal would be quite interference and 
lightning strike tolerant/resistant. And a single centrally located low 
band station could cover most of the CONUS day and night. The reality is 
the system would be best placed on PEP as well as strategic secondary 
stations since they have the hardened infrastructure already in place.

However, IBOC uses that part of the spectrum for something and a station 
transmitting IBOC on AM would not be able to send the subcarrier without 
shutting down IBOC. That might be a moot point as many stations have 
shut down IBOC anyway, some have shut down at night to eliminate 
interference, and installations have all but stalled.

Mike McCarthy
Chicago

On 8/25/2011 11:59 PM, Robert Paine wrote:
>   Here's another that "will never happen" and maybe the idea is full of holes, but at least it's an attempt: Since the analog VHF channels are freed up, why not utilized part of that spectrum as a dedicated national, regional and state alerting system. Any combination of voice and digital could be used. Since the old V channels had pretty decent coverage, a good transmitter might have a good reception area. When necessary, satellite booster xmtrs would fill in the gaps.
>   I'm a very non-technical person and if this has already been proposed in one form or another, the Emily Letilia disclaimer applies: nev-ver mind.
>
> Bob, KA3ZCI