[KNPB TV studios]

KNPB Goes Digital!

At 3 PM PDT on September 29th, 2000, KNPB (PBS, Reno, NV) turned on it's digital TV signal. This comes 17 years to the second from the station's original sign-on in 1983. KNPB becomes the 22nd (of 310) PBS station in the country to broadcast in DTV. Here's the story of the DTV transmission plant installation.

Revised 2-14-2001 Our permanent reduced-power construction permit recieved from the FCC!

In 1997, the FCC ordered that all TV stations in the US must convert from the traditional analog TV transmission system in use since the '40's to an all-new digital transmission format. This transition was to take place over a period of years, with all stations having digital transmission on the air by 2003. In 2006, the analog broadcasts are supposed to cease, but that is not really likely until 2010 or later.

Ever since the announcement of Digital TV (DTV), KNPB has been working to be a leader in this area. As a PBS member station, KNPB has much to gain from DTV: High-definition TV (HDTV), multicasting (up to 4 (and maybe more) programs being broadcast in the spectrum previously occupied by one.), Datacasting, interactive ('enhanced') television and more. As a result, KNPB developed an infrastructure that would put them on the fast track to DTV. The turning on of the digital signal is not just a culmination of many years of planning and hard work. It is a beginning of an ever-expanding world of better television!

It has been asked, 'How do you eat an elephant?'. The answer is, 'One bite at a time.' And so it is with digital TV. Up to this point, much of the work has been on paper. Studies were done to determine just what would be required to broadcast this new signal. A permit to construct the transmission facility had to be obtained from the FCC. And of course, funds had to be raised to purchase the necessary equipment. (The FCC mandated this conversion, but never told broadcasters how to pay for the substantial costs of the conversion!) Finally, a plan was drafted for an initial low-power DTV transmission plant. After sufficient funds had been raised to obtain the necessary equipment, it was purchased. The goal was to begin transmitting digital on September 29th, 2000, exactly on the 17th anniversary of the station's initial sign-on!

There was an agonizing wait for the FCC to approve the construction of our DTV transmission plant. During this wait, the equipment arrived, so we had it on hand. The permit finally arrived on Monday, September 18th, just in time to make our goal!

[View of Reno from atop Red Peak]

Here is a picture of the City of Reno, as seen from our tower site, which ia known as Red Peak. You can see some of the mountains that completely surround the city. The first order of business was to get the antenna installed on our existing tower. It is now Thursday, September 21st. It was a cold, windy day on the mountaintop. The installation crew consisted of Fred Ihlow, the Chief Engineer; Charlie Anderson, maintenance engineer and consultant; and myself.

[Assembling an antenna panel on the ground]

The antenna system consists of four broadband panel antennas made by Kathrein Antennas of Germany. Each panel required some minor assembly on the ground before being raised up on the tower. Because we are on a mountain top, the tower does not need to be very tall. In this case, it is just 40 feet or so to the base that holds our channel 5 analog transmit antenna. Fred is an experienced climber, something rare among engineering managers. This saved us considerable time and money on this project.

[Fred Ihlow mounts an antenna panel]

It did not take long to put up the antenna. Everything went together as designed. Here, Fred is mounting the fourth and highest panel on a side-mounted pipe on the tower. After the panels were in place, the combiner was installed behind the antenna panels. Phasing lines were run from each panel to the combiner. All RF connectors were the European 7/16 DIN, something which is rapidly becoming common in this country. While Fred and Charlie worked on the antenna installation, I worked on terminating the tower end of the transmission line (7/8 inch hardline). I also helped when it was time to hoist up a new panel or some other heavy part.

[The completed DTV antenna]

It's a good thing we were able to work quickly. We got the antenna up, and the transmission line installed just in time to miss a cold, driving rain. There were even a few flakes of snow in that rain. In any case, this is what the completed antenna looks like.

[Transmitter as recieved at the studio]

Now, our attention turned to the transmitter. Since the transmitter only puts out 160 watts average power, it is not physically large. (Keep in mind, though, that there are random power peaks of 640 watts or more in this particular modulation scheme, 8VSB. So, the transmitter was grossly overbuilt for the power level.) It runs off of 208 volts single phase power at about 11 amps (2200 watts input power. Not very efficient!). A second, 120 volt circuit runs the exciter, upconverter, and control logic. The box sitting on the table in front of the transmitter is the Zenith 8VSB modulator.

[The transmitter is loaded into a truck]

Because the transmitter weighs about 400 pounds, it would be very awkward for two people to handle. Therefore, it was decided to disassemble it into major subassemblies for transport. This was easy to do, as the transmitter was modular to begin with. The two stacked modules, to the right of the cabinet, are the RF power amplifiers.

[Reassembling the transmitter on site]

On Tuesday, September 26th, Fred and I transported the transmitter to the site and reassembled it. This went very well, and we were done sooner than planned.(Here, I am attaching cabling to the lower RF PA module.) The inside end of the transmission line was terminated (N connector), and we called it a day. On Wednesday, we returned and did the AC power wiring. As this is not the permanent transmitter, or the permanent location, we used 10/4 SO cord to get power to the transmitter. Again, this task was completed more easily than planned.

[The DTV signal as observed on a spectrum analyzer]

Just after 1:30 PM on Wednesday, September 27th, we were making power into a dummy load. At 2:30 PM, we first transmitted into the antenna, to verify that the antenna is working OK (It was), and that no interference was being caused to certain types of medical monitoring devices in use at some hospitals. (No interference was anticipated, and none was actually observed. This check is mandated by the FCC.) After approximately half an hour, we shut down the transmitter. The picture here shows a textbook-perfect 8VSB DTV signal!

[Pushing the 'big' button!]

The big day finally arrived, September 29th, 2000. At 3 PM, we would officially turn on our DTV signal. Earlier in the day, Fred went to a local TV dealer where a festive ceremony would be held. I went up to the transmitter site, and performed a test transmission. Everything worked perfectly, and they had a signal the instant I touched the 'on' button! We tested both HDTV and multicast signals, and all seemed in order. So, we all returned to the studios to regroup.

When the time came to do the sign-on 'for real', Charlie Anderson, the Operations Supervisor Evie Chmura and myself would be at the transmitter. We agreed that Charlie would be the one to press the button. He had participated many years before in the development of a major television technology, the videotape recorder. Here was his chance to make more television history! (Charlie has been a major player in the station's DTV planning from the very start.) So, at exactly 3:00 PM, a ribbon was cut at the TV dealer, and the button was pressed!

On the mountain, we were rewarded with a flawlessly functioning transmission plant. PBS was feed plant. PBS was feeding us a special header to introduce the world of Digital television to the Reno 'masses' (We actually knew of two people who already had DTV receivers!). We met the header with perfect timing! (We were switching blind, so we didn't know if we would catch it exactly on time.) Unfortunately, something was wrong at the TV dealer, and the signal never did get received there. Although the 'dog and pony show' part was a flop, the signal did appear and is still on the air as I write this. History has been made!

At the time, KNPB was the smallest PBS station in the country to be transmitting a Digital TV signal. Were were also the fourth smallest station of all TV stations in the country to be transmitting a Digital TV signal!

So, where will KNPB go from here? the first thing we did was to conduct a field study of our signal, to see how robust it really is. Reports from other parts of the country were not encouraging. However, our study is showing that the DTV signal performs very well, even at low power. Basically, if the viewer is line-of-sight or nearly so with the transmitter (Which is the case for most of Reno), they should be able to get a good signal with a simple antenna. This includes indoor reception with a set-top antenna. Our study is still in progress, but we believe that we will have no problem providing high quality. high relaibility Digital TV programming to the Reno area!

We were required to file an interim report with the FCC on the progress of our low power study in early December. Convinced that we are on the right track, the FCC issued KNPB a permanent permit to operate at lower power in mid February, 2001. Although the power level we will ultimately be required to operate at is twenty times the power we are now using, we believe that KNPB is the only station in the country to be authorized to run less than the legal minimum DTV power!

Stay Tuned, this is only the beginning!

KNPB-DT TV Technical info

KNPB DTV Team