[EAS] Alerting options

[Cross, Robin]

In the 60s Florida had several AM stations use 10 Hz fsk set up for EBS.  I was told it worked flawlessly.  +5 & -5 Hz.  It could still work with ascii.

Robin Cross
Chief Engineer KCUR
816-235-2880 W
816-235-2865 Fax
816-235-1551 Receptionist

Mike McCarthy wrote:

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

_______________________________________________
This is the EAS Forum Discussion List

Please invite your friends to join our Forum!
http://lists.radiolists.net/mailman/listinfo/eas

And, remember the main page: http://eas.radiolists.net