MARCH 1998
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
Hammett & Edison, Inc. - Dane E. Ericksen, P.E. - (707) 996-5200
LeBLANC - David A. Hill - (650) 574-4600
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
Doty-Moore RF Services, Inc. - Donald Lincon - (415) 388-5678
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 speaker will be Fred Jones, the developer of the Ramsa DA7 digital audio mixer by Panasonic. Fred came into the business as a user of equipment so he had a good idea of what people wanted. Our thanks to Leo's Pro Audio for making the arrangements.

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.

On feb 26th Comark, Dolby, Divicom, Microwave Radio, and Dielectric Communications gave a free day long seminar at Dolby Labs in San Francisco. It was an excellent session. Dolby proposes building level information into digital content to inform the receiver of the desired level settings appropriate to the content. Dielectric and Comark have done joint tests on the S/N impact of uncorrected group delay in filters. You get wiped off the map if you don't correct for it. Even phase and amplitude ripple on transmission line are more troublesome than you would think. Microwave Radio detailed the signal margin penalty of using digital microwave. Dane Ericksen explained that you couldn't light up on a channel without considering the effects on spillover from the digital signal into adjacent channels. Divicom covered the encoding issues and the usage of the digital bandwidth. In talking with Dielectric, I found out the 500khz resolution of the DTV mask may make it somewhat easier to meet the spec.. Dane Ericksen passed out a summery of the key features of the 6th Report and Order Reconsideration.

On the same day as the meeting at Dolby, there was a marathon meeting at the San Francisco Planning Commission on the permit for the construction work needed to mount the antennas at Sutro Tower. The permit was approved but additional legal maneuvering is anticipated. Each broadcaster is working out the details of modifications needed to their space in the Sutro building. Some equipment has already arrived and it looks like the November 1 date will be met by several, if not all, of the stations

While the straight SF broadcasters haven't been able to plan an NAB dinner for years, the bent ones are doing fine. The dinner for the National Association of Gay and Lesbian Broadcasters will have its NAB dinner April 7th at Sam's Town, 5100 Boulder Hwy. Social hour from 1830 to 2000 with dinner at 2000. For reservations call 1-888-293-8454.

The channel filters for digital television will have virtually no effect at the edge of the channel. The reason it that the group delay would have a fatal impact on the 8VSB signal. The filters don't kick in until 750 khz to 1250 khz away from the channel. That means that the FCC mask has to be met by the transmitter. That's something of a daunting task when you consider that values of -35 to -38 dB are typical of what a transmitter will do. The IOT has a very broad response so there really isn't much rolloff near the channel edge.

The dynamic correction we've been hearing about may distort the peak to average ratio of the signal and truncate peaks and effectively reduce system S/N. The correction may provide little more than a carpet to sweep signal under while simultaneously reducing power and coverage.

Buried in the 8VSB modulator is a filter which converts the 8 level digital signal to an analog signal. It is the intersymbol interference filter (ISI). Without it the required bandwidth would be infinite. With it, the system put 2 pounds of YNW in to a one pound bag. Once in awhile 7 dB spills out. If you believe in perpetual motion machines and alchemy, 8VSB should present no problem.

Please be advised that you can't walk from the front of the LVCC to the LV Hilton. Construction is underway. You have to go halfway back toward the meeting rooms and then go over. Allow twice the amount of time.

The chapter 40 web page is at and is maintained by Tim Pozar.

The keeper of the chapter 40 email address list is Warren Reese his address is

Warren worked for the KPH in Bolinas which was one of the last coastal Morse sites. He has photos of KPH on his web page at

Mountaintop Engineers Plan Annual Pre NAB Vanilla Pudding Run at ZZYZX
The 9th annual Vanilla Pudding contest is on again in ZZYZX, which is between Barstow and Las Vegas. The April 1st sand dune rock downhill ski run, done while balancing cups of vanilla pudding on the skis is in the grand tradition of radio transmitter site sports. Check out the details at