November 1996


Roy Trumbull - Editor

Bill Dempster - Artist


This month our speaker will be Peter M. Langtry of Lowney Associates. He will deal with regulations regarding the operation, maintenance, and management of underground fuel tanks.
As usual our luncheon will be at Sinbads. 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.


DEC - No Luncheon meeting. But there will be a joint evening meeting with SMPTE at KRON-TV. JVC will do show and tell on their Digital S format. The meeting will be Thursday Dec 12th at 7 PM. KRON is at 1001 Van Ness Ave., San Francisco.


KQED-FM will serve as the LP-2 station for EAS in San Francisco. KSJO will be the LP-2 for San Jose.


As of today we have no test message for the weekly or monthly EAS tests. I've contacted Frank Lucia of the FCC but so far no response. Stan Harter of State OES felt the committee should come up with a script for the coordinated monthly test but that the weekly one could be something like: "This is a test of the Emergency Alert System from (your call letters and city of license)" That would be sandwiched between the header and the end of message.


I'd like to remind you that when our founder, Howard Immekus passed away, that a scholarship fund was established at the College of San Mateo in his name. When Dick Parks died we decided it was better to support the existing fund rather than start a new one. The reality being that it is hard to accumulate enough money so that the interest will result in a significant scholarship.
Donations should be made to College of San Mateo, Office of Special Programs and Services, 1700 W. Hillsdale Blvd., San Mateo, CA 94402.


The FCC allocation table for DTV has created quite a fuss. A rival table has been generated by the Broadcast Caucus. Both contain unattainable super powers for VHF channels which are intended to replicate their present coverage. The 8 VSB system creates signal peaks that are 7 dB higher than the average operating power. Antenna gains much above 30 tend to warm the clouds. The largest UHF transmitter is 280 KW. It must be derated by a factor of 5 to allow for the peaks mentioned above. That would be only 56 KW. Even with no transmission line loss with a gain of 30 antenna it would only give 1.68 megawatts. Yet some of the average powers in the allotment table run to 2, 3, 4, and 5 megawatts.

Another problem is that some stations are assigned an adjacent channel to operate on. Initially it was felt they could share a common antenna.The stations can't have overlapping signals without creating problems, yet we have no square filters. Using real world filters with skirts, a DTV below an NTSC would result in a portion of the NTSC vestigial sideband being clipped. A DTV above an NTSC would play mischief with the NTSC aural carrier.

Part of the UHF band has been given over to land-mobile users. If you try to operate on an adjacent channel you'll desensitize co-located receivers. The requirement to suppress your signal spillage into adjacent channels by 60 dB is sufficient when your neighbor is a distant TV station but you may have products that will break the squelch in many land-mobile receivers.

There is the need to be frequency locked to adjacent channels especially when the lower channel is an NTSC channel. The pilot in the DTV signal will produce a rainbow stripe in the NTSC picture. Loran-C and GPS have been suggested.

The government is hot to auction off channels 60-69 as soon as possible. The fact that many of the TV translators which bring TV to small towns operate on those channels hasn't made much of an impact . Likewise the eventual giveback of channels 2 to 6 will eliminate the far reaching signals that are used by rural communities to maintain ties to large cities.

Local stations, which may serve out to 80 or 100 miles, will find they're only able to cover from 37 to 55 miles when operating on UHF due to the nature of UHF propagation.

Anyone attempting to receive a DTV signal without an outdoor antenna and a lo-noise amplifier will probably get nothing. If there is any reception with set top antennas it will only be for the first 10 or 15 miles.

The power required to replicate coverage for an existing UHF station is 12 dB below their current NTSC peak power. There is concern that may drastically change must-carry status.

But we're off in a rush to claim these channels while they're offered to us. I fear that we'll all be diminished by this course of action and in the future wonder how it was we set off down this path.