[EAS] Alerting options - WWVB?

[Tom Spencer]

Tom Taggart wrote:
> Not much signal in the east...very slow data transmission
> mode.

Depends on time of day; also the antenna and ERP are factors.

At 06:00 UTC, WWVB covers about 95% of the entire Western Hemisphere

http://tf.nist.gov/timefreq/images/radiostations/wwvb-large/0600utc.jpg

This would correspond to 1:00 AM EST.  12 hours later:

http://tf.nist.gov/timefreq/images/radiostations/wwvb-large/1800utc.jpg

Pretty much the whole continent west of the Alleghenies...

Add power or improve antenna for better daytime coverage.

There's a set of maps covering the entire 24-hour period (2-hour 
intervals) at

http://www.nist.gov/pml/div688/grp40/vb-coverage.cfm

And the only reason the data rate is so low at 60 kHz is because it's at 
60 kHz.

At 110 kHz carrier, you could manage a 16k00A9W (or -D) signal, I 
think.  The exact carrier frequency and exactly how to modulate it would 
have to be studied...

As long as there's no visual information (all text or audio), all you'd 
really need is the same bandwidth as a "normal" AM broadcast signal (10 
kHz audio;  20K00A3E) Just how good do you want//need the alert audio to 
be?  At telco-quality, it becomes:  M=3kHz; 2M = 6kHz; so 6K00A3E.  
Would the "duck farts" pass down a POTS line without too much distortion?

-- 
Tom Spencer