Roy Trumbull - Editor
Bill Dempster - Artist
Advertisers for this month's newsletter are:
Zack Electronics - (800) 998-3947
Advanced Marketing - Frank A. Santucci - (650) 365-3944
Riggins Electronics Sales - George Riggins - (662) 598-7007
Orban - Rick Sawyer - (360) 715-1913
MARCOM - Martin Jackson - (408) 768-8668
William F. Ruck, Jr. Broadcast Engineer - (415) 995-6969
Communications Law Center - Philip M. Kane - (650) 369-7373
RF Specialties of California - Bill Newbrough - (888) 737-7321
Hammett & Edison, Inc. - Dane E. Ericksen, P.E. - (707) 996-5200
LeBLANC - David A. Hill - (650) 574-4600
Pacific Research & Engineering Corp. - William Hopkins - (760) 438-3911
Keith Davidson & Company - Keith Davidson, CSBE - (707) 648-0412
Improbable Missions Fource - Mike Schweizer - (888) 4-ISDN4U
Svetlana Electron Devices - George Badger - (800) 578-3852
TFT Inc. - Jesse J. Piatte, Jr. - (408) 727-7272 x504
Audio Accessories - Rosie Alexander - (510) 787-3335
Brill Electronics - Marcie Mearns / Field Sales - (510) 308-1248
Brill Electronics - Larry Shore / Inside Sales - (510) 834-5888
Scala - Michael Wm. Bach - (541) 779-6500
Scala - Everett E. Helm, CPBE - (541) 779-6500
Harris - Ed Longcrier - (800) 315-7285
Anixter - Judy Conner - (510) 489-7430

This month our program will feature the latest from Cutting Edge Audio.

As usual our luncheon will be at Sinbad's. Sinbad's is just south of the Ferry Building on the Embarcadero near the foot of Mission Street. Please RSVP to Karen Prasek at Zack's: 408-324-0551 x126 as we've been running out of tables and chairs. We meet at 11:30 and are seated at 12:30.

Future Meetings
The analog signal we've been using for over 50 years is a repetitive scanning pattern. Once the receiver syncs up to it, it is pretty much a no-brainer to display. The sound is separate and manipulated on the basis of the 4.5 Mhz intercarrier spacing. ATSC is quite different. It is based on fixed packet length but what goes in those packets could be video, sound, data, program schedules, access codes, or even a few things not thought of yet. The receiver must sort out the packets and send them to the appropriate destinations and then the electronics have to make sense out of them.

The visual compression works on the basis of sending entire pictures as seldom as possible and, for the most part, sending only difference information to update the last picture sent. The audio compression is entirely different in that it reduces the data by eliminating that part of the signal which is likely to be masked from audibility by one mechanism or another. I defer to Dolby for a more detailed treatment of AC3.

There is an essential conflict between the two compression schemes that impacts lip sync. The receivers will line up the time stamps of the video and audio packets and present them at the same time but the sync may not be satisfactory for critical viewers.

Of some concern is encoder latency. If I receive digital video from my network and separate analog or digital audio to go along with it, I'll need to encode the video into an MPEG stream. The audio will go to an AC3 encoder and both encoders will go to a mux. If the video encoder latency is greater that the AC3 encoder latency, I'll need a rubber band buffer when I put the two signals into the mux to match them up or else I'll need some way to diddle the time stamps. These are rather speculative problems as no one has taken delivery of an SDTV/HDTV encoder or seen any incoming signals from their respective networks.

I expect that initial programming won't be in full AC3 as there isn't an announced scheme for transporting 5.1 channels of audio to affiliates. We'll probably see mainly surround sound that will have to go through a Pro-Logic decoder and then be encoded as an AC3 stream.

Many years ago, either in a tabloid or in TV Guide was a story about someone in the UK receiving old TV programs from outer space. I asked a friend on the Internet about it.

Hallo Roy. yes, there was a big to-do about thirty years ago when some London 'inventor' invited the press to view what he called live television from the USA. He herded the press into a room where they saw, on standard British 405-line TVs mark you!, station IDs from a number of American TV stations. It earned him some fame at the time from a rather uncritical public. Afterwards someone noted that one of the stations apparently coming in over the airwaves was (I forget the call letters but it was called 'The Eyes of texas' or something similar) and this station had been off the air for two years before his claimed reception. A technical journalist was all ready to denounce this man a few years ago as a hoaxer but got worried at the last moment in case he was still alive and sued for libel.

I'm pretty certain I have cracked the story anyway. In the early 1950s there were a lot of USA magazines circulating in the UK and one of them (I forget the reference but I have the issue, about March 1950 or 51) published a two-page spread of American TV station ID photographs. By an amazing coincidence, all the stations that this inventor "received over the air" were ones in this photo spread. Clearly he had just rigged up a camera and a closed circuit TV system and duped the reporters in that way! Clever in a way. A couple of years ago one of our dumber papers told the story of an old TV which only received old programmes from the 1950s (but the ones they described in the article) were _all_ ones which had been repeated on TV in the last few years. Some press men are verygullible, it would appear. And I'm a journalist too, but a very cynical one!!!!

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Webmeister Tim Pozer has the current newsletter plus newsletters all the way back to 1996 at: