Archived Tech-Notes
Published by: Larry Bloomfield & Jim Mendrala      The following are our current e-mail addresses:
E-mail = or
 We have copied the original Tech-Notes below as it was sent out.  Some of the information may be out of date.

DTV Tech Notes

% Larry Bloomfield & Jim Mendrala

(408) 778-3412 or (805) 294-1049

E-mail =  or

February 19, 1999  DTV Tech Note - 026


Surprise, Surprise, Surprise.  Here's another one in less than a week.  We said we'd publish these when there was something to say.  Sharing experiences, knowledge or anything else relating to DTV, HDTV, etc., with your fellow engineers: That's what we are all about. We will send this to anyone asking, just E-mail us. There is no charge for this Newsletter.  Welcome to all new subscribers -- we've got quite a few.  We're now over 250.  If you are receiving this newsletter and want to get off the list, just e-mail us that request. We hope everyone will participate in all ways with comments, experiences, questions and/or answers. This is YOUR forum!   Past issues are available at:  WWW.SCRI.COM


In response to the article entitled "Is the Peacock Changing Colors?" from our last edition, we received this e-mail:

"Every time there are layoffs, budget cuts, etc., there is also talk of selling the Peacock [or part of it].  I equate it to removing the engine from a car, pushing it down a hill and declaring, "See how cheap it is to operate!"

The old days of spending lots of money to maintain high programming and engineering standards, in return for a reasonable profit, are long gone. The cable channels are trying to look like the broadcast networks and the broadcast networks are trying to look like cable channels.  And it seems to be working.


Anonymous, NBC-TV, Burbank

(Editors note:  This is how we received it.  When I worked there, there were more than 475 technical people on permanent staff.  It is unlikely that there are 75 at this time.)


(Editors note: (1) The material in this issue is all by Larry Bloomfield.

(2) If this story looks familiar, (here's the legal part) a condensed version of this article appeared in the January 1999 issue of Broadcast Engineering, copyright 1999 Intertec Publishing in the Beyond the Headlines section.  Having been a Chief Engineer at a station that depended on translators to cover a good part of our DMA, I have asked Broadcast Engineering if I may share the unedited version here, which goes on to point out a serious situation facing the viewers in the state of Utah.  This situation, I'm sure will face others in areas where translators are very much a way of life.) 

Utah TV - New and Old - A tradition of cooperative efforts

If you've ever been there, the mention of Salt Lake City will probably bring back memories of a very beautiful, well planned, organized and symmetrically laid out city, founded, in hardships by a group of very hearty, dedicated and focused people.  It's not just the junction of I-15 and I-80, it's the nation's 37th largest demographic marketing area (DMA), which, in addition to all of Utah, covers parts of four other states, and has some very rough and "unfriendly" RF terrain.

Like most all other western states DMA's, many of the viewers do not "see" the main broadcast station. Dave Hudson, Chief Engineer of the CBS O&O station, KUTV mentioned that some viewers see his station relayed through 5 to 7 translators.  My first clue as to how the DMA is "really" covered beyond the "metro" area was from the large number of translators scattered in, around and through out the state that duplicate the programming from most of the stations in Salt Lake City.  In an impromptu survey I conducted of the participating Chief Engineers, Utah has well over 560 licensed translators and more that haven't gone through paperwork mill.

Despite all this, the broadcasters in "the City" by the lake with the highest saline content on the planet have not lost any of that original pioneering spirit, focus, direction or cooperation when it comes to serving their DMA or the digital delivery of their television signals. In late October of this past year, eight of the nine stations serving the Salt Lake City area announced plans to build a joint digital television transmitter site.  Farnsworth Peak named for the Utah native and American inventor of today's electronic scan TV system, Philo Farnsworth, in the Oquirrh Mountains under the name of "DTV-Utah."

Only one station in the Salt Lake metro area is not participating, KSTU-13.  Curious, I tried to reach their Chief Engineer, Al Schultz, but got the General Manager, Duffy Dyer, instead.  The first thing out of Dyer's mouth was:  "We're an O&O and have been told by corporate not to comment."  While trying to find the phone number to someone at corporate who could comment, I said:  "It would be in the viewers best interest if all transmitting facilities in the Salt Lake metro area were co-located," to which Dyer said: "We could spit and hit either KSL's building or the new DTV building."  If that's the case, who can disagree with Dyer's closing remark:  "We're not doing anything that is a disservice to the viewers?" 

The project won't come cheep.  I overheard one Los Angeles broadcast engineer, after going on line November 1st, say, "These DTV transmitters draw anywhere from 3 to 4 times the power compared to our old NTSC transmitters."  Due to the sometimes nasty winters in and around Salt Lake City and the very healthy appetites of eight new DTV transmitters, getting power and maintaining it to "The Peak" won't be an easy chore for the local power company.

The cost to build the DTV-Utah site is estimated at more than $7 million.  That price tag will include a 330-foot tower (see blueprint), antennas, buildings, and "emergency" power systems.  Farnsworth Peak is located atop a mountain range that extends from the South, north to I-80 and is westerly of Salt Lake City.  The site is 9273 feet above mean average sea level, which puts it about 5000 feet above the Salt Lake Valley floor.  The new DTV site is adjacent to KSL's existing transmitter site.  The joint venture has elected KSL Television to be the managing partner.

The project had its beginnings when DTV-Utah was organized last year to evaluate the feasibility of co-locating a transmitter site.  The study was conducted by Spectrum Solutions Group of San Francisco and all Utah television stations (and permit holders) were invited to participate.  Similar to the observations I made in my feature about selecting DTV Antennas in last April's issue of Broadcast Engineering, the feasibility study showed distinct economic and technical advantages for co-location.

The all too familiar story of weather will determine when construction can begin.  Completion is expected prior to November, this year.  Each station will then begin broadcasting its digital signal as soon as they've acquired and installed the required equipment to do so.  In speaking to several of the Engineering bosses at the participating stations, some plan to broadcast from the site as early as this fall.

Greg James, manager of DTV-Utah and vice president for engineering at KSL, said, "The expense of converting to digital broadcast is significant for each station. The transmission facility is only one small part of that expense.  Stations in the group have already begun the transition, but it will take time to duplicate all cameras, switching equipment, relays, and other technology." James noted that some stations would make the transition prior to FCC deadlines.  "Utah audiences are technically sophisticated and expect the best," he said.  "In addition, we must worry about the limited construction season on Farnsworth Peak, and we should be well into a digital environment prior to the heavy demands of the 2002 Winter Olympics."

Some of the Utah based engineers I spoke with about this project feel that Farnsworth Peak will improve their signal reception into some locations, especially in fringe areas along the Wasatch Front, where current signal quality is weak.  It certainly makes sense and reduces reception problems to provide viewers one place to "point" their new DTV antennas, if they can electronically see Farnsworth Peak.

According to my survey, there are:  690,000 TV Households in the whole DMA with 498,000 in the Metro Area.  According to Mike Grover, Chief Engineer at KJZZ-TV:  "I estimate that about 70% of the people "can" receive us directly from our transmitter.  However, many people "choose" to watch us on cable, even in areas where we have a strong primary signal.  Keeping this in mind, I'm guessing that less than half of our total viewership actual watch us on our primary transmitter."

The numbers Phil Titus, Chief Engineer of KUED gave me were almost identical saying his NTSC transmitter covers 72% of the area with 50% Cable penetration in the metro-Salt Lake and 55% Cable penetration in whole DMA.

When asked what percentage of the viewership watch via translators, Grover said 30% and Titus said 28%.  They both followed that, without taking a breath, and sounding like an echo, "These figures may be a little deceiving, since most rural cable companies rely on the translator network to get our signal."  That's over a quarter of their respective viewing audiences.  Utah's not alone!  These figures also hold true for most all DMAs in states stretching from the Eastern slopes of the Rocky Mountains to the Pacific Ocean and it wouldn't surprise me if there were small, but extensive translator networks in the Appalachia's.   

All translator viewers and those who get their cable via translators are in a rather precarious situation.  First, none of the translator networks were put up over night. According to Utah's translator guru, R. Kent Parsons, TV & FM Translator Field Systems Engineer and Specialists for the University of Utah and Vice President of the National Translator Association, the Utah translator network has developed over the past 42 years.  Most are not particularly accessible, especially come wintertime.  Been there -- done that!  Next, the FCC is taking away some of the frequencies typically assigned to translators, causing major re-channeling problems (Channels 60-69). 

Based on his years of experience with the Utah translator network, Parsons has developed a plan to shuffle things around so the existing NTSC translator network, with frequency changes, can continue to serve the area.  Parsons told me he has met with the FCC and, "they have accepted my plan, but," he added, "it will take about $3 million just to keep the existing rural NTSC translator channels (560+) on the air.  With the advent of DTV and the lessor number of channels available, there's no interference-free room for DTV translators-anywhere in Utah."

In talking to Parsons, he did say one other thing that made a whole lot of sense:  "The term "Secondary Service" is a misnomer.  It isn't "secondary" if you haven't got anything else."

Between the frequency changes in NTSC, the total lack of coverage for DTV stations via translators and ownership questions, viewers are going to suffer!  Ownership questions are becoming a nightmare.  The stations own some of their translators, but not all.  Dave Hudson sited a very typical example.  He said:

"KUTV is on approximately 114 translators; we hold the licenses for 5 of them.  The overwhelming majority of the translators in Utah have been purchased and maintained by county governments, community groups, cities, and individuals." Translator ownership ratios are very different for each station, but the totals are very high, nonetheless. It is not common for a station to have a total number of translators anywhere from 60 to 120.  Hudson added:  "The men who maintain this network of translators perform an amazing feat."

It's been my experience that the contributions to the "organizations" that are necessary for maintenance and upkeep have dwindled and the local governments want out of the translator business.  It will take lots of dollars, which the stations may not have or wish to divert, right now, away from converting their main broadcast facilities over to digital.  Due to the waning interest and funds, the other translator owners probably won't be too successful in raising the capital to address DTV, even if the frequencies were available.   

Looking to the government won't be much help.  These are the people who want to take away local-into-local satellite service, a possible answer for some of these viewers.  It seems that Congress only sees the FCC as a Golden Fleece.  Speaking of "fleece," I need not dust off my crystal ball to forecast that fleecing is what appears to be very much in our DTV future.  The FCC needs a wake-up call to address this issue.  Good luck!  When it comes to these kinds of issues, the sleep they seem to be in makes Rip Van Winkle's look like a catnap.  They've got to give on one of the issues.  If they continue to do nothing, there's going to be a lot of folks left without TV of any kind.  All one has to do is become familiar with the history of the people who settled Utah to know they don't and won't put up with very much government baloney.  

Stay tuned to Beyond the Headlines, as we'll be giving you progress reports on both the DTV-Utah project as it moves along.  It is lining up to be a model.  And Parson's is in the process of implementing the DMA's translator shuffle, which should prove to be interesting in its self.

The Utah television engineering community, in this cooperative effort, has up held the highest tradition of a people who went there with nothing but push carts and in covered wagons; willing to join together and cooperate to achieve a common goal.  It is their kind of cooperative engineering effort that should be commended in this day and age of everyone wanting to "do their own thing." Making it easier on viewers will help to insure a much smoother transition to this new technology and should be an example to broadcasters else where to get it together.  As Mike Grover, Chief Engineer of KJZZ said:  "It has been a good experience to come together as a group of broadcasters with a common goal.  While each station will certainly benefit from this alliance, I think the real winner in all this is the viewer."


Flannery and the Blarney Stone!

Cervantes would be proud.  Righting wrongs or setting the record straight!  After hearing that "bandwidth is the future," from Bill Gates, one tends to perk up when something relating to bandwidth, or the efficiency there of, comes across the desk.  One such story tweaked the interest recently about an Irish girl who either has a great gift for us all or has succumbed to the effects of the Blarney stone. 

New equipment is constantly on the drawing board designed with speed in mind to make our Internet access and e-mail go faster.  Remember the days of the 600-baud modem?  But hardware isn't the only approach to speed.  In researching information on bandwidth management, an interesting story came to light that was a refreshing surprise.  Hardware isn't the only approach to be taken.

According to a story in the London Times, a Sixteen-year-old Irish schoolgirl, Sarah Flannery, has proved the next generation of speed is in the software.  History tells us that a trio of students attending MIT developed the current code that runs e-mail, back in 1977, long before young Sarah was born. 

As a child of the cyber age, it shouldn't come as any surprise that this young Irish lassie has devised a new code that will send e-mail ten times faster, and with no change in the level of security that today's data protection code offers.

Here's the kicker.  Unlike some software geniuses, Flannery says she is considering publishing her discovery rather than applying for a patent.  She says that she doesn't want people to have to pay for it.  Needless to say she is being inundate with job and scholarship offers.  The Times of London has ignored our requests for a photo of Flannery.  Perhaps it all for the best.  If she lived in this country, congress would probably investigate her, thinking she is a subversive.

On the other side of that coin, a few days later a second story said that Flannery's approach would take ten times longer than existing software.  It will be interesting to see if this is fast bits or fast Blarney.


Broadcaster, Bandwidth Broker or both? - The New Technology at NAB 99

There should be little question in anyone's mind that most of the focus at NAB this year, on the television side of the exhibition halls, will be on all the new bells and whistles in the wonderful world of digital television.  In addition to keeping the NTSC plant on the air and working, a whole new parallel operation will begin to unfold, according to the FCC's timetable, in additional markets across the land. If the DTV broadcaster of the future is considering multichannel operation, that new parallel operation will have several paths.

The pioneers in the first phase still have many unsolved issues and new ones are cropping up every day.  Those stations who are bumping up the local NTSC signals and passing through the network feeds have not encountered many problems, but two areas which seem to be a source of consternation to most stations are the local origination of high definition programming and multicasting.  

One Director of Engineering and Technology for a group owner said that his company hasn't developed a business plan that addresses multichannel.  His competitors are addressing that issue as this goes to press. One cannot help but wonder if he's ever heard of the early bird and the worm?

The strongest argument for multicasting is if that a broadcaster can deliver more viewers to his advertisers by the offering a variety of programming over a number of channels, they'll get more of the finite advertising dollars in their market.  It is immaterial if these are different types of programs or if the station broadcasts its fair, spread over, or repeated during, the evening, like near video on demand. Delivering viewers is what brings in the bucks!

ATSC (digital television) permits the transmission of as many different programs or services as they can be squeeze into the 6 MHz, but there are tradeoffs and the broadcaster must decide the quantity vs. quality level he'll settle for.  This can be either a positive or a negative in the equation. The key is the management of the available bandwidth.

Bandwidth is a very precious resource, irrespective of the transmission media.  Bill Gates even said that the future was in bandwidth.  If you can believe Gates, bring the women and children in and set the hounds out to protect and manage your bandwidth so you can get the most out of it.  If you don't, be assured that your competitors will.  It's simple: By optimizing the data transmitted, more can be put in the maximum allowable bandwidth at any given time. 

The transmission media, be it terrestrial, fiber, copper or satellite, has physical bandwidth limits.  It should come as no surprise that, as standard practice, a number of program Bitstream's are multiplexed together to be either send down a fiber or to a transponder.  The same is true in multicasting.  Good practice is to insure that this number of program Bitstream's, when multiplexed together, will approach the bandwidth limits of what ever the media.  It also stands to reason that each program source may well have different or changing bandwidth requirements. 

The smart engineer will keep his eyes out for equipment that will permit bitrate scalability so Bitstream's can be parsed.  This Bitstream parsing can occur either during transmission or in the decoder.  Bandwidth scalability is a particular case of bitrate scalability where part of a Bitstream, representing a part of the frequency spectrum, can be discarded during transmission or decoding.

Some program material requires a constant bitrate.  Constant bitrate (CBR) streams are buffered regulated to allow continuos transfer of coded data across a constant rate channel without causing an overflow or underflow to a buffer on the receiving end.  It is the responsibility of the Encoders Rate Control stage to generate bit streams that prevent buffer overflow and underflow.  CBR encoding can be modeled as a reservoir: variable sized coded pictures flow into the bit reservoir, but the reservoir is drained at a constant rate into the communications channel.

CBR bandwidth management is used to address those types of programs, such as live sporting events, where the content and bandwidth requirements are uncertain.  The broadcaster then decides, in advance, the maximum bandwidth limits that will be devoted to the program to insure quality.  This is much safer than depending on the statistical multiplexer to do the "right" thing. This is a quality of service decision on the broadcasters part.   

The most challenging aspect of a constant rate encoder is, yes, to maintain constant channel rate (without overflowing or underflow a buffer of a fixed depth) while maintaining constant perceptual picture quality. CBR is not a very efficient technique.

Not all scenes in a video presentation require encoding at the same CBR in order to achieve good picture quality.  By capitalizing on this varying need for bitrate by moving bits generated from complex scenes in one program to less demanding areas of other programs the bandwidth can be optimized.  The problem with CBR is that peaks may occur simultaneously, which potentially could create overloads in channel capacity resulting in picture degradation. 

To avoid this kind of problem in CBR, a statistical multiplexer can process the actual encoded bit stream to reduce the peaks and hide potential artifacts in areas of the picture were they ill go unnoticed.  VBR can be "on the fly."  The simplest form of variable rate (VBR) Bitstream's does not obey any buffer rules, but will maintain constant picture quality.  Constant picture quality is easiest to achieve by holding the macroblock quantizer step size constant (e.g., level 16 of 31).  In its most advanced form, a VBR stream may be more difficult to generate than CBR streams.  In advanced VBR streams, the instantaneous bit rate (piece-wise bit rate) may be controlled by factors such as local activity measured against activity over large time intervals (e.g. the full span of a movie), or instantaneous bandwidth availability of a communications channel.

Statistical multiplexing takes the bit distribution model to four dimensions: horizontal, vertical, temporal, and program axis.  The 4th dimension is enabled by the practice of multiplexing multiple programs (each, for example, with respective video and audio Bitstream's) on a common data carrier. In the 4-D model, bits may be distributed according the relative complexity of each program against the complexities of the other programs of the common data carrier.  For example, a program undergoing a rapid scene change will be assigned the highest bit allocation priority, whereas the program with a near-motionless scene will receive the lowest priority, or fewest bits.  An examination and reaction to microblocks and its' contents within the MPEG-2 structure are required to achieve the best level of VBR statistical multiplexing.  The accompanying diagrams will help you to understand this approach.

There are two parts to bandwidth management.  The broadcaster must first decide what quality of service is desired for each programming service.  The ability to affect the bandwidth must be at one of two levels: the service level and down to the program level.  This decision obviously must be tied in directly with the program scheduling software.  The choice of where is necessary as the quality desired for each of the various programs on the same service may differ in accordance with type and content, yet some services may never need to be changed.  The traffic system software must be able to access the available bandwidth at any point in the schedule, permitting the broadcaster to make an informed and intelligent decision in allocating what is available.

Once the decision is made, the traffic and control system software should be able to execute bandwidth allocation commands to the appropriate hardware.   In addition to this, the traffic system should be able to deliver last minute changes in the bandwidth allocation requirements to the hardware, keeping in mind that there will be latency in changing from one bandwidth to another.  All this must be done seamlessly and without drawing the viewer's attention to any action by the broadcaster.

The second part of bandwidth management is virtually automatic and solely hardware related.  This is where the statistical multiplexer employs the parameters decided on by the broadcaster in the preceding paragraph to actually allocate the bandwidth.  Hardware is a purchasing decision and should be done in accordance with the standards and architecture of the broadcast system. 

Controlling the mix of traffic on congested media is critical in delivering reliable performance for important applications and users. Several bandwidth management solutions are available today that claim to solve the congestion problem. Not all products, however, provide the requisite level of functionality to control the bandwidth of real world traffic.  Bandwidth managers must control bandwidth for entire classes of traffic, not just individual connections.  It is important to avoid bandwidth starvation through weighted priorities to ensure that all connections receive some bandwidth and judicious management of the bandwidth must be maintained under all traffic conditions, not just worse-case scenarios.  Last, but not least, a good bandwidth manager must integrate with a firewall to support encryption.

There is an obvious and apparent need for sophisticated software to integrate a bandwidth management system that will work in a multichannel environment, while optimizing the transmission path by effectively communicating with the plants compression equipment.  In this light, the practical approach to bandwidth management is in the areas of constant and variable bandwidth management, but with the option to select which ever will best suit the needs of the moment.  Needless to say, this ability to switch must be seamless to maintain the quality and integrity of the program material.  In addition to this, in the effort to achieve the goals of optimum bandwidth management, it is necessary to be able to splice MPEG-2 programming and, again, do it seamlessly.  These are the only ways to insure the highest quality in the transmission of the program material. 

The keys to managing bandwidth are in the exchange of knowledge.  The knowledge of the bandwidth requirements for the signals your are dealing with (incoming, out going and/or locally originated).  The knowledge of the availability and capacity of the equipment with which you will deal with theses signals and the knowledge of what is at the other end of the transmission "pipeline."  This is where software system steps in and does its' job, disseminating this knowledge and a whole lots more.

Bandwidth management and the software that runs it, must be abler to address the plants hardware configuration, setting up the defaults for each program service in the lineup.  As sporting events scroll up on the schedule, the bandwidth manager allocates an appropriately larger amount of bandwidth to ensure high quality. However the same service does not get the same amount before or after the sporting event.  Bandwidth management has to happen at both the program service and individual event levels.

As events are scheduled, an operator would set up the defaults for bandwidth management according to the needs of the service.  The user could also set up event specific bandwidth requirements in the scheduler to override the defaults on an as-needed event-by-event basis.

There are several manufacturers of bandwidth management equipment whose equipment will operate at the level and complexity required of the discerning user of modern day communications equipment seeking to get the most out of their particular system.  In addition to the many functional similarities between manufacturers, each has designed into their equipment their own distinct operating characteristics and abilities that must be taken into account at the time the system is launched.  It would not be prudent to recommend one manufacturer or system over the other, as each will fulfill a specific need to achieve a particular end.

No one is in business to loose money.  Anyone who transports digital material, irrespective of its content, would do himself or herself a disservice if they did not at least look into the claims that have been presented here.  The broadcaster who is even remotely considering multichannel operation at any time: the cable operator who wants to optimize their system without the costly replacement of the distribution network: and the satellite systems operators who want to get more through their spacecraft: need pay heed to this information.  You can bet that your competitor will!  Begin a dialogue with those companies who can supply equipment and can deliver the specifically develop sophisticated software to perform these functions.  You'll be glad you did.

The accompanying drawings are reprinted by permission and are courtesy of Imedia.  I'd like to thank the following companies who helped in the preparation of this information:  (hardware)  DiviCom (, IMEDIA (, Phillips (www.Phillips.Com)  and V-Bits (  and for software: SunUp Design Systems (


The Silent Key

It is always a grim task when it is necessary to share about the passing of a family member, friend or associate.  John DeWitt, JR., a major contributor to the electronic industry passed away at the age of 92 in Nashville, Tennessee earlier this year.  DeWitt, a pioneer in the broadcast industry, made significant contributions to science by bouncing a radar signal off the moon and back to earth.  Conceiving the idea as early as 1940, DeWitt continued to try his theories while working as an engineer at WGN-Radio in Chicago.  His first attempt to obtain moon reflections were unsuccessful.  He used a 138 MHz transmitter and receiver that he had developed for WGN.  

Success would not elude DeWitt for very long.  On Jan. 25, 1946, after several evenings testing and adjusting other radio equipment, his military-sponsored group heard the first reflections of radar waves from the moon, proving that electromagnetic waves could penetrate the Earth's atmosphere.

Once the test results had been confirmed by independent experts, news reports put the feat in the same class as the development of the atomic bomb.  Time magazine declared, "Man has finally reached beyond his own planet."


The DTV Tech Notes are published for broadcast professionals who are interested in DTV, HDTV, etc., by Larry Bloomfield and Jim Mendrala. We can be reached by either e-mail or land lines (408) 778-3412, (805) 294-1049 or fax at (805) 294-0705.  News items, comments, opinions, etc., are always welcome from our readers; letters may be edited for brevity, but usually not.     --------- <<<

DTV Tech Note articles may be reproduced in any form provided they are unaltered and credit is given to the DTV Tech Notes and the originating authors, when named.