[EAS] Uses for your old EAS unit

[Dale Lamm]

Dave,

The right way to do this would be to bridge a monitoring input across
the main audio input on the second unit (at your transmitter site). Be
sure the incoming filters on the second unit allow for two sources, the
"genuine" agency (such as NOAA) and the relayed alert from the first
unit (at your studio, with your call letters in the ID field).

If my understanding is correct, the second unit will hear the VHF NOAA
alert header and begin the relay process. Simultaneously, the studio
unit hears the same VHF NOAA alert and begins it's relay process.
Because the second unit is downstream from the first, it controls what
goes into your broadcast transmitter. Shortly thereafter, the second
unit hears a duplicate header arriving on the main audio line (from the
studio unit), and discards this alert because it was "already heard".

EAS units apparently make the decision to relay or discard dupes as soon
as the header bursts are decoded, since the headers contain all the
detail needed to act on a message. I was also under the impression that
alerts with similar priorities would not pre-empt one another, but be
acted on sequentially as long as they were not dupes.

Regardless, your comments indicate someone has tried this and
experienced problems. I happen to have four EAS units available for
bench testing (two different models among the four). Let me make a few
tests. Thank you for pointing this scenario out.

Also, the notion of waiting till you've heard the EOM bursts before
initiating a relay is curious. All the relevant alert info is in the
header (except the voice message, which the EAS unit cannot decode). I'm
unsure how waiting for the EOM makes things any better.

Dale

-----Original Message-----
From: eas-bounces at radiolists.net [mailto:eas-bounces at radiolists.net] On
Behalf Of Dave Turnmire

On 7/8/2012 12:55 PM, Dale Lamm wrote:
> ...6. Put the old one in series with the new one at a different 
> location (the transmitter?). Attach one or two very important
monitoring inputs.
> Now you've got two chances to relay an important alert. [Dale] ...
I have seen this tried in some other scenarios  and it does NOT work as 
expected.   Say box #1 picks up an alert on its monitoring input and 
forwards it out its program audio output.  This program audio gets fed
on your STL to the transmitter site and once there, feeds the PROGRAM 
input of the site's new EAS box.   After all, it is primarily the 
program audio source... having some EAS audio added is secondary to the
program audio function.  Only problem... the EAS box at the transmitter
site only monitors the "monitor" inputs for EAS audio... it doesn't
expect EAS audio on the program input. So... it doesn't know that the
alert it DOES pickup on a monitor input duplicates one coming in on the
program input.  Assuming for the sake of argument that you didn't have
any delays programmed on either box, the two alerts arrive more-or-less
at the same time, and at some point after the alert starts on the
program input, it is interrupted by the alert arriving on the monitor
input.

The exact details depend on the delays involved and the eccentricities
of the particular EAS boxes involved regarding at what point in the
incoming alert does it start forwarding the alert (ie, after the initial
data tones, or after the EOM?  Former is quicker, latter is "safer").  
But one way or another, you sound bad on the air. And if you happen to
have someone downstream relaying your signal, who knows how THEIR box
reacts to this mess.

Dave

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