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Test equipment

Last year's NAB showed a sudden upsurge in the number of monitoring companies producing products designed to monitor digital videostreams, 8VSB modulation,
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Last year's NAB showed a sudden upsurge in the number of monitoring companies producing products designed to monitor digital videostreams, 8VSB modulation, detected HDTV signals and other new signal types that are recent developments in the broadcast industry. Most of these are now becoming standard items in the broadcast engineer's test gear arsenal.

The computerization of test gear is a trend on the increase. However, manufacturers are still producing stand-alone products and probably always will.

Unlike last year, there were not a large number of new “stream testers” introduced. The effort this year on the part of most companies centered on solidifying themselves as the experts in a particular area, and making the equipment they already have more user-friendly and feature-rich.

Sencore, one of the companies who pioneered digital video test equipment, had some advancements. Its field strength-measuring device, the AT1506 (See Pick Hits, pg. 82), is an upgrade of last year's AT986. Significant improvements include an increased recording capability of the signal you're measuring, and, more importantly, global positioning system receiver built into the meter. Now you don't have to try to remember the color of the buildings or some other landmark where you took those field strength readings.

Sencore also had another new DTV test item, an ATSC-compliant baseband signal source. At first glance, it seems like only a transmitter manufacturer would be interested in such a thing. But on second thought, what about testing that digital STL or doing a “proof of performance” on your DTV transmitter?

Again, Rohde & Schwarz advanced its DTV test line by showing the DVQ-M real-time tester (See Pick Hits, p. 82). Unlike many test items that only provide you with parameters, the DVQ-M is a quality tester, designed to tell you what the quality of the signal is, in reference to set standards. If you're dropping I-frames or the motion vectors aren't working, this will let you know. By comparing the signal under test to the standards, deeper levels of measurement capability are possible.

Audemat showed the DTVA01. Lest we forget, DTV's sound is shaping up to be at least as important as the picture. There seem to be few few-channel sound testers available, so this box is somewhat unique in the industry.

Acterna showed its DTS-100, which offers extensive, real-time analysis and capture in an easily portable package. The DTS-100 is capable of in-field analysis of MPEG-2 DVB/ATSC transport streams, running from a laptop plug-in box via the PCMCIA interface.

Audio Precision showed its line of PC-controlled audio measurement systems consisting of its System One, System Two and System Two Cascade, as well as a new version of its APWIN monitoring software for those systems.

One area that has received less attention that some others is the measurement of the actual output power of a DTV transmitter using 8VSB modulation. Digital modulation, in general, does not lend itself to the standard methods of “caloric” power measurement; that is, heating up some form of element and interpolating the power from the heat. Whether it's your digital cellular or PCS phone, or your HDTV transmitter, obtaining the true power in the digital domain can be quite a challenge.

To assist the industry with this effort, two major manufacturers have teamed up; Bird Electronics and Harris Corp.

Bird has a new series of meters that are designed to measure the true RMS power of the DTV signal. The “BPM” series (for Broadcast Power Monitors) uses a transmission line section installed at the transmitter output that connects to a 1 RU-high, digital monitoring unit. This system looks at forward and reverse power and also does efficiency calculation, power ratios, etc. It can be connected to a PC, so you can do some system analysis.

In dummy loads, Bird introduced a new series of high-power loads called the Digital Air Series, which claims to handle a 10dB peak over their average power without failure. Again this is designed to allow for the effects of digital modulation.

Tektronix has spruced up the WFM700 monitor to make it a multiformat measurement device, and also allow increased capability when connected to a computer. The front-panel controls area is much more attractive and considerably more user-friendly than before.

Videotek showed the VTM 330E, a rack-mount frame with up to 15 cards in it. Each card has the ability to monitor a videostream in real time by looping the stream through the card. Different cards measure different types of streams and the frames can be stacked. Each frame, or a series of stacked frames, connects to a computer, which can monitor the quality of the stream, and do detailed analysis, again in real time. The computer also can log any intermittent problems, time-stamp them, and tell you what they were in great detail. The connection to the computer is TCP/IP, so you can use the Internet if you want to tie the frames and the computer together.

For certain, today's test gear has something for everyone, or perhaps one should say, a way to test, monitor, analyze, troubleshoot, define or generally discover whatever you want to know about any signal that your plant can generate.

Paul Black is Engineering Manager of the San Francisco International Gateway teleport for Loral Skynet.