A monthly newsletter by Society of Broadcast Engineers Chapter 48

November 1996


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Contents

Chapter 48's Next Meeting
The October 1996 Meeting
Upcoming Chapter 48 Meetings and Events
RF Flanges and How to Ruin Them
Computer Related Acronyms - Part 2 of 3
EAS Update
Hams Face Exposure Limit
Three States Approve Overlay Area Codes
SBE Offers Professional Liability Insurance
Etc.

Chapter 48's Next Meeting...

...will be held on Wednesday, November 20th, starting at the noon hour. Meeting place will be the Coco's Restaurant, located southeast of the Havana and Parker roads intersection in Aurora. This month's program will feature a very important update on the EAS system due to go into effect January 1st. Local chapter nominations for officers will also be held. Be there or be nominated!

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The October 1996 Meeting

Our October get-together was combined with our fellow engineering groups SMPTE and SCTE for a half-day of seminars and free lunch on Thursday, October 19, at the beautiful KUSA, Channel 9 studio building on Speer Boulevard.

Attendance was quite light from Chapter 48, but good overall, with all of the seats filled by the time the first presentation got underway. Due to the light turnout by Chapter 48 members, attending chapter officers Vice-Chairman Eric Schultz and Secretary/Treasurer Bill Harris opted not to hold nominations for Chapter 48 officers in 1997. Rather, nominations and elections will be held at the November meeting on the 20th at Coco's Restaurant.

It was definitely a day of advanced technology for those attending. There was discussion of Sony's Serial Data/Digital Interface (SDDI); Asynchronous Transfer Mode in backbone transit and video transport; MPEG encoding to provide compressed services via satellite and cable; the future of telecommunications from the perspective of AT&T and an FCC regulatory activities and changes update from Leo Cirbo, Denver FCC Engineer in Charge.

To top off the event, KUSA Vice President of Engineering Myron Oliner presented a tour of the station's facilities.

Our thanks to all of the folks making presentations, KUSA and Myron Oliner for the meeting place, and the meeting planners for making this informative and timely program a possibility.

Hope you'll join us on Wednesday, November 20 at 12:00 noon at the Coco's Restaurant at South Havana and Parker Road. We'll have nominations and elections of Chapter 48 officers for 1997 and a very important update on the Emergency Alert System, due to go into effect January 1st!

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Upcoming Chapter 48 Meetings and Events

November 10 (Sunday) SBE Chapter of the Air, 0000 GMT, 14.205 mHz, Hal Hostetler WA7BGX - control station.

WEDNESDAY November 20, 1996 Coco's Restaurant, 12:00 noon; South Havana and Parker Road - Chapter Officer nominations and elections; EAS update - Jack McKain, KWGN-TV and Rebecca Willman, FCC

EARLY DECEMBER MEETING!

December 11, 1996 12:30 pm - lunch meeting to be held at Bennett's Pit BBQ at 13000 E. Arapahoe Rd, Englewood 1:30 pm - KTVD-TV's studios at 11203 E. Peakview Ave., just off Arapahoe road in Englewood - FCC Inspection Vehicle - Jon Sprague, FCC

January 1, 1997 (Wednesday) First day you MUST have a new EAS encoder/ decoder operating at your station and monitoring at least two sources.

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RF FLANGES AND HOW TO RUIN THEM

D. W. Sargent
D. W. Sargent Broadcast Service
Chapter 28

There has been much written about installing and maintaining coax transmission line over the years. Topics range from how to pressurize the line to how long the horizontal run should be in relation to the vertical run, to what manufacturer you should use. This article is going to deal with a subject that applies to any type of transmission line, i.e., FLANGES.

Have you ever looked between the flanges of rigid or semiflex coax and seen a space between them? I'll bet you grabbed a couple of wrenches and tightened them until the bolts squeaked. This is a good way to create a discontinuity (at best), and create a situation for burning (at worst).

The flange has two components, the first serving to connect the flanges together (main body) and the second as the RF contact (contact ring). The RF contact ring extends beyond the flange body. This contact ring is not massive like the body of the flange, in fact it is down right delicate when compared to the body.

The gap between the body of the flanges will be between 0.020" and 0.040" when the contact rings are touching. This distance will vary depending on the size of the coax. There is an O ring groove in each flange, but we will not be concerned with that here other than to say it is a very important component and should not be damaged.

What happens to this contact surface when you really bear down with the wrenches on the bolts? You can smash the surfaces down. If you tighten one side tight before the opposite side, you will mash one side more than the other. If you ever reuse this flange with another, the contact surfaces will not properly mate. This condition will result in a high current density situation because you won't make contact on the entire surface. Arcing can be the result.

You may have heard about "warped" flanges. I doubt that given the small area of the RF contact ring versus the very large part of the body of the flange that you could damage the body. You can certainly damage the contact ring (and probably the O ring) by over-torquing the bolts. What will this do to the electrical characteristics of the line? For one thing you will have destroyed the smooth surface contact, and that will result in an impedance "bump." This will be a discontinuity and the magnitude of VSWR that results will depend on the frequency--at UHF it will be higher than at VHF. Of course, it isn't going to help you at any frequency! And if you get too carried away you will be making your RF contact through the large portion of the flange instead of the RF contact ring, resulting in a significant VSWR change.

Some engineers have said that they have observed systems where the bolts themselves were serving as the RF contact. This will eventually result in burning of the bolts and nuts which will cause the flanges to become loose and you will have a real burn-up situation. If you don't torque the bolts enough the contact surfaces will not be able to carry the current, will heat up, and eventually burn. If the bolts are loose enough, the surfaces won't meet and arcing will occur, and the O ring will not be compressed enough to prevent leaks in the pressurization system.

This discussion applies to EIA and EIA type flanges only. There are other types of flanges that have been used over the years that are different and have their own set of problems, but these are disappearing and we will not address them here.

--Reprinted from Chapter 53 (South Florida) Newsletter

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Computer Related Acronyms - Part 2 of 3

Eric Schultz, Chapter 48

EMS - Expanded Memory Specification - A memory management technique that allows computers to exceed the original 640K DOS limitation. Programs requiring EMS are becoming uncommon.

EOF - End Of File - A byte of data indicating that the end of a file has been reached.

FAQ - Frequently Asked Questions (pronounced "fack") - A list of common questions and answers pertaining to a specific topic. Before posting a question to a computer newsgroup, it's best to find out if the newsgroup has a faq.

FAT - File Allocation Table - The portion of a hard drive where the map of the drive's directories and files is stored.

FPU - Floating Point Unit - Also know as a math co-processor, the FPU is processor dedicated to mathematical functions, reducing the processing demands on the CPU. The Intel 80386 was often accompanied by an 80387 FPU. The 80486 and Pentium processors have built-in FPUs.

FTP - File Transfer Protocol - A set of instructions used to transfer files between computers.

GDI - Graphics Device Interface - A programming interface that allows software to draw fonts and graphics on the computer display.

GUI - Graphical User Interface - The interface used by the computer to interact with the user. Microsoft Windows and Macintosh System 7 are examples of GUIs.

HTML - HyperText Markup Language - The scripting language used to create World Wide Web pages.

HTTP - HyperText Transfer Protocol - The set of instructions used to transfer data between World Wide Web clients and servers.

IDE - Integrated Device Electronics or Intelligent Drive Electronics - The hard drive interface system most commonly used in PC compatible computers.

IMHO - In My Honest (or Humble) Opinion - An abbreviation used in internet chat, email or news.

IRC - Internet Relay Chat - A protocol for internet chat.

IRQ - Interrupt ReQuest - A signal from a hardware device such as a modem or a disk drive used to get the the CPUs attention.

ISA - Industry Standard Architecture (pronounced "eye-suh") - The bus design found in PC compatible computers. ISA bus slots are found in both 8- and 16- bit formats.

ISDN - Integrated Services Digital Network - A digital communications specification, allowing data rates up to 128bps.

JPEG - Joint Photographic Experts Group - A compression method for reducing the size of image files. JPEG is a lossy form of compression, meaning that once the image is compressed, the original quality of the image cannot be restored.

LAN - Local Area Network - A small network of computers, usually limited to one building. LANs can be connected to other LANs, WANs or to the Internet.

LSB - Least Significant Bit - The bit carrying the least weight in a binary number. Usually this represents the value of one.

LUN - Logical Unit Number - Used to distinguish between multiple SCSI host adapters in a computer. Each adapter has a unique LUN.

MIPS - Millions of Instructions Per Second - A measurement of microprocessor speed.

MFLOPS - Millions of Floating Point Operations Per Second - A measurement of microprocessor speed.

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EAS Update

Leonard Charles

As the night of party hats and noise makers draws near, broadcasters cannot forget that New Years Day 1997 signals more than the start of another calendar. All broadcasters must have EAS equipment installed and operating on that festive day.

The next step is to begin contemplating programming of that equipment. With only the National Presidential message mandated for immediate relay, broadcasters will need to decide what additional alert messages they will relay and whether they will relay them manually or automatically. A Local Plan developed by broadcasters and Government Emergency sources in a local area will hold the information to make those decisions. Information on what types of messages to expect and where they will come from will help the broadcasters make those decisions.

As a broadcaster, now is the time to get involved in formulating that Local Plan.

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Hams Face Exposure Limits

Chapter 124, Portland

The new FCC RF safety standards that become effective in January are causing considerable consternation in the amateur radio ranks. Strongly opposed by the ARRL, the regulations affect ham installations with over 50 watts PEP. Some hams, recognizing the close proximity that many of their antennas have to the general public, are taking this to mean the end of all operations at powers over 50 w. The Commission appears to be attempting to calm the storm somewhat in recent correspondence with the League. They stated that they'll provide "straightforward methods for amateur operators to determine potential exposure levels" by year's end, and are relying on hams to police themselves in this matter. Meanwhile, the ARRL is reviewing whether to seek reconsideration of any aspects of the FCC decision. Also, it appears that push-to-talk portable and mobile radios will not require the routine evaluation for compliance with the RFR limits. Are time-averaging exposure meters the next must-have ham shack accessory?

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Three States Approve Overlay Area Codes

Neal McLain, Chapter 24

Three states - Maryland, Pennsylvania, and California, - have formally approved the adoption of overlay telephone area codes. In all three cases, the decision to approve an overlay, instead of a geographic split, was the outcome of a big political battle. As in previous overlay-vs.-split battles, the arguments were much the same:

Businesses and municipal governments generally prefer overlays so they won't have to change phone numbers on letterheads, sales brochures, building signs, vehicles, web sites, etc. Cellular and paging companies prefer splits, arguing that it isn't "fair" if their customers have to use numbers in the overlay area code. This argument is also put forth by competitive wireline providers such as cable television companies and long distance carriers seeking to offer local telephone service.

Consumer-protection groups favor splits, arguing that overlays discourage competition in the local telephone-service market. "The overlay was opposed by Pennsylvania's consumer advocate and its small-business advocate, who said it could stifle competition. They said people would be unlikely to switch to a competitor if they had to move to a new area code."

Consumers object to any plan which requires dialing more than seven digits for local calls; hence they usually prefer splits. Incumbent wireline companies rebut this argument by noting that subscribers near boundary lines must dial 11 digits for local calls across the boundary, a situation which becomes increasingly common as area codes are split into ever-smaller areas.

In the end, the decision rests with the state-level regulatory body responsible for utility regulation.

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SBE Offers Professional Liability Insurance

SBE is pleased to offer a new member benefit. Group rates on professional liability (errors and omissions) insurance. Contract engineers, and others who do not always work as an employee when providing broadcast engineering services, should find this coverage extremely valuable. The program is called "PROINSURE," and is administered by MIMS International, Ltd. of Towson, Maryland. The coverage is under-written by Employers Reinsurance Corporation and is tailored specifically for broadcast engineers. For more information and a no-obligation quote, call Debbie Zarzecki at (800) 899-1399.

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Newsletter Committee

Bill Harris.......(303)756-4843 email: BHarris4@IX.netcom.com
Garneth M. Harris..(303)756-4843
Andre' Smith.......(303)871-4204 email: ansmith@du.edu

Views expressed herein do not necessarily reflect the official positions of the Society, its officers, or its members. We regret, but are not liable for, any omissions or errors. The Denver SBE Newsletter is published approximately twelve times per year. It is prepared with a combination of text and graphic data. Submission deadline is 10 days before the last day of each month. Other SBE chapters are permitted to use excerpts if attributed to the original authors, sources, and/or the Denver SBE Newsletter.