[EAS] EOC emergency links to stations and other EOCs

[Dan Peek]

Hi John,

I started the discussion which has been interesting and informative. I've learned a few things although I haven't been able to read through everyone's posts as thoroughly as I would have liked. What I had in mind was a VSAT system that had a national frequency and didn't require a precisely pointed satellite dish. I'm thinking about some of the sought after TV spectrum (maybe the guard bands?) or something like that. Receivers are easily available for that. It might still be low bandwidth and unidirectional. I was dreaming of something that could be included in a cell phone which would warn people who were outdoors and hopefully they could pass the message along. Maybe not ideal.

Dan Peek, 3ABN LPTV engineer

Dan Peek, Engineer
Three Angels Broadcasting Network, Inc.
3391 Charley Good Road
West Frankfort, IL 62896 USA
618 627 7635 direct
618 218 2035 cell
www.3ABN.org -- Watch all our channels streaming live

On Mon, Aug 29, 2016 at 10:23 PM, John Willkie <johnwillkie at hotmail.com> wrote:
>There was some discussion of systems that wouldn't work, and then geo-sync VSAT was discussed and dismissed, essentially based on the need for getting to an uplink and needing highly directional antennae. I was too deep into my code to take the time to respond at the time.

>The basic requirements, as I see them:

>    * Links must be available 24/7, particularly during an emergency
>    * Links must work indefinitely even if there is no power available at all points between nodes
>    * EOCs must be able to confirm that messages were received at the far end
>    * EOCs must be able to confirm that messages were (or were not) aired, or that airing was deferred.
>    * Links must be able to carry audio, text and data in real-time

>I see two ways to accomplish this.

>I'd first like to mention the simplest topology: using the digital bandwidth available in off-the-shelf satellite emergency phones. These are hand-held devices that link with Low Earth Orbit satellites (such as those operated by SPOT for remote sensing). The units have an essentially non-directional antenna, and they're battery powered.

>Caveat: bandwidth tends to be very limited (measured usually in single-or-double digit k's), and transport tends to be non-IP. Voice quality is low, and some units are outgoing-only (ie, emergency outgoing calls.) To get a message to such units, you would connect using POTs or another sat phone. Also, individual calls would need to be made to every remote pickup point, unless a "dispatch voice" function is offered.

>The preferred solution, is simply to use VSAT terminals, with symmetrical data packages carrying IP datagrams. Use it to send audio, data, and low-frame rate low resolution video in, say, 1 Mb/sec. There is no need for an uplink larger than the VSAT terminal that can do 20 simultaneous credit-card transactions at the same time at a gas station while also delivering "Gas Station TV."

>Sure, satellites fail from time to time. So, use VSAT dishes that send and receive simultaneously on two birds at the same time.

>And, you avoid the vagaries of terrestrial mw and FM transmission over long distances, local power issues, smoke, etc.

>John Willkie

>__________________________________________________________
>The EAS Forum Discussion List is hosted by the BWWG (Broadcast Warning Working Group). http://eas.radiolists.net
>Please invite your friends to join our Forum! The sign up is at: http://lists.radiolists.net/mailman/listinfo/eas
>___________________________________________________________