[BC] Digital TV dispatches UK coastguard

[Hershberger, Dave]

Way back in the late 80s, when digital video was new and standards were
proliferating, and during the 8 bits vs. 10 bit debate, there was one
proposed standard which would have raised havoc with distress frequencies.

It was CCIR 601 video (27 MHz sampling), at 8 bits, using 8B9B block coding.
So the clock frequency for serial transmission was 27 MHz * 8 * 9/8 = 243
MHz, a distress frequency. Screen rooms would have been required to house
all digital video equipment had that standard come into widespread use.

Of course, it could more easily be the 9th harmonic of a 27 MHz clock, which
is what MPEG decoding uses. That hits the 243 MHz distress frequency
dead-on.

Dave Hershberger 
Principal Engineer 
AXCERA
Tel: 530-272-HDTV (4388)
Fax: 530-272-4505 
dhershberger at axcera.com <mailto:dhershberger at axcera.com> 
AXCERA. Axcessing the new era of digital communications. www.axcera.com 
960 McCourtney Road, Suite C, Grass Valley, CA 95949-7423

> [mailto:broadcast-bounces at radiolists.net]On Behalf Of Chris Gebhardt
> Sent: Wednesday, February 15, 2006 12:42 PM
> To: broadcast at radiolists.net
> Subject: [BC] Digital TV dispatches UK coastguard
> 
> 
> From:
> http://news.yahoo.com/s/nm/20060215/od_nm/britain_digibox_dc
> 
> LONDON (Reuters) - Lifeboats and a helicopter scoured the sea 
> to track 
> down an electronic distress signal -- only for coastguards to 
> discover 
> it came from a British retiree's faulty digital television 
> box on dry land.
> 
> The coastguards were scrambled after a rescue coordination center in 
> Scotland picked up what it believed to be a distress signal 
> coming from 
> the sea off southern England.
> 
> But communications experts later traced the signal to the digital 
> television set-top box in the home of 67-year-old Mary 
> Donaldson in the 
> western town of Plymouth.
> 
> "We sent a helicopter out and two lifeboats before we discovered that 
> the signal was in fact coming from inland," a spokesman for the 
> coastguards said Wednesday.
> 
> Donaldson was at the cinema when the experts tracked down the signal. 
> "We sent two officers there to investigate and they were still there 
> when the lady came home," the spokesman said.
> 
> The incident late last month was the second time this year a 
> set-top box 
> in Britain has been blamed for a distress signal. Communications 
> regulator Ofcom said both boxes were being analyzed but stressed such 
> cases were extremely rare.
> -- 
> Chris Gebhardt
> VIRTBIZ Internet Services
> chris at virtbiz.com | (866) 4-VIRTBIZ
> 
> _______________________________________________
> This is the BROADCAST mailing list
> To send to the list, email: broadcast at radiolists.net
> For sub changes, archives and info on this other lists: 
http://www.radiolists.net/