EAS Notification Question...

[RicoGregg]

A few minutes ago, the EAS Notification System for Los Angeles County was set off by the National Weather Service. I was watching my local cable system (Time Warner), and everything worked like it was supposed to (it was a severe thunderstorm warning). Emergency notifications have truly come a long way since the old CONELRAD systems. It makes you marvel at the technical advancements that have happened since then. It also makes me marvel at one other thing:

Why is the audio quality so gawdawful bad and so damn hard to understand? ???

You would think in this day and age that the audio quality on an EAS Alert would be crystal clear. It's worse than the static-ky, spurious days of AM radio in the 50s & 60s.

Why is it like this? ???

 

[oaktree]

I believe it has to do with the cheapest possible low-pass bandwidth and bitrate known to man that will allow enough spectrum to make contact closures on digital EAS units, take over all transmitters on FM & AM as well as cable headends and all cable channel distribution ... from Oxnard. It is "low voice grade" and may be at or below 12,000 kilobits of resolution, while regular AM is 22,000, low end stereo is 32,000, FM is a little higher, CD at 44k, on up. The higher the bit rate digitally (as the EAS machines are,) the better the audio quality. They are used infrequently, so, that much bandwidth and pipeline is expensive when you consider one agency (NOAA) and the NWS paying the freight ... so, nationally, it gets to be expensive.

The state uses UHF/VHF radio (you can hear it on your scanner) and the signal is relayed through repeaters around the state. (Also expensive.)

They aren't using RE-20 mikes either ...

 

[jal41]

Your cable system should be monitoring the two LP stations. I understand in California the network is a mix of AM and FM stations, but in Los Angeles the network is AM radio stations (KNX and KFI), whereas here in Georgia the network is all-FM radio stations (which allows for better quality).

http://eas.oes.ca.gov/PDF/Directory-Web.PDF

In the Atlanta area, the local LP's quit relaying the NWS due to the long safety tips and information that are a part of the warnings (which I do not agree with). They now relay all EAS alerts from GEMA (Georgia Emergency Management Agency), which includes an abbrievated. Both the NWS and GEMA systems are computerized sythnized voices for weather warnings (a GEMA employee reads missing child alerts, which are know as Levi's Call in Georgia).

Most likely the use of AM radio stations is the problem. I don't know if the California network relays NWS or records their own messages for EAS.

 

[The Beave]

RicoGregg,

I have your answer... I have studied the EAS and ESPECIALLY the weather service end (thanks to the dept. of homeland security) The frequencies of 162.XXX band are a set of protected frequencies originally that were sandwiched between 2 way business bands, and below that band is the aviation/military aircraft bands 118.XXX-144.XXX.

The console systems for the weather service is a PC based platform with a small podium mic. The quality is horrible like you said, but also the platform can convert text to voice. (vocoded)

Most NWS channels have an ERP of less than 1kw, and just like the 2-way band
they have squelching issues.

Call your local NWS and talk to the Engineer or Meterologist In Charge to visit with them. I'm more than certain they can help.

 

[kenglish]

The broadcasters are usually required to monitor a Primary (AM or FM), usually a Secondary (another AM or FM), and a mandatory (if receiveable at all) local NOAA WeatherRadio channel.

Studios are usually located (as we all know) in some noisy office complex, or at the transmitter (talk about yer' RF noise!)....so AM reception is often lousy. FM reception can be made pretty good, assuming management wants to spend the money (get the PD on your side, telling him how good the "monitoring" of the competition will be). NOAA is often harder to deal with, since it requires a vertically-polarized receive antenna on 162 MHz....close enough to the low end of the upper VHF band (channel 7 starts at 174 MHz), but wrong polarity to pick it up on the regular TV antenna.

Stations pass the audio (as well as the alert data) as a "Daisy Chain", so any weak link will affect the signal going downstream.

A tuned, shielded-loop, or similar, antenna helps with AM reception. Wellbrook, in the UK, makes some for serious DX'ers. Belar, and others, make them for commercial use. Ramsey makes a "Signal Magnet" kit. FM just needs a good FM-only antenna. And, sometimes you can get the "feeder" (like an STL) of the NOAA broadcasts on 400-420 MHz government (NTIA) channels, or rent a phone line.

Wade Antenna (in Canada) makes a commercial-grade antenna for NOAA (162 MHz) use....or, an old VHF Marti antenna might do. You can order them through CATV supply companies. And, SITCO (Simplicity Tool Co.) says they can supply a commercial-grade VHF preamp, bandpass-tuned to the 162 band, as a special order, which is great if you are a "very suburban" (out in the country) station .

 

[kenglish]

BTW, all this might be a moot point.....
Homeland Security is re-inventing the system. What will happen is anyone's guess.

 

[notalkallstatic]

Homeland Security is re-inventing the system. What will happen is anyone's guess.

It will probably become a complete disaster, and won't ever work properly again...oops...did I say that out loud?

 

[kenglish]

We've had some major complaints, from Cable viewers, about the quality of the audio from KSL-AM (State Primary and Local Primary source) during alerts. But, we can't seem to get a "legal opinion" on whether they could take the AM-HD audio feed. The digital audio would sound much better, and an HD Radio receiver would still revert to analog reception if the IBOC failed.

Also, I wonder if the data channel could carry some extra, detailed info for their CG crawls. That's the other complaint we get...."Just another interruption, but not enough details to make it worthwhile".

 

[The Beave]

Also, I wonder if the data channel could carry some extra, detailed info for their CG crawls. That's the other complaint we get...."Just another interruption, but not enough details to make it worthwhile".

The limited info on the crawls is the info sent to the stations via the weather service. Maybe it's designed to have people turn on the weather radios or a full service news station.