Antenna design, translators and interference also on the agenda

In its final day, the IEEE Broadcast Technology Society’s Fall Symposium examined modern transmission facility remote control and monitoring technologies, high-power multistation FM antenna design, and more.

REMOTE MONITORING AND CONTROL AIDS BROADCASTERS

Paul Shulins

Paul Shulins

Burk Technology’s Paul Shulins led off the sessions with an examination of modern remote control and monitoring technologies in broadcast plants.

“There are several goals attainable with today’s monitoring and control systems,” said Shulins. “Broadcasters want to consolidate monitoring and control for all remote site functions. They want to manage national, regional, and local network operations centers or ‘NOCs.’ They want to use autonomous capabilities to react to status changes without human intervention, and also to manage alarms effectively.”

[Read: IEEE BTS Broadcast Symposium Examines Digital Radio]

He observed that SNMP was the great enabler for 21st century remote control and monitoring.

“Remote control designers have embraced SNMP,” said Shulins. “You can monitor a facility halfway around the world if it has an internet connection.”

He noted that the sophisticated remote monitoring available today can be very useful in spotting trends that might indicate pending problems and automatically initiate a corrective action.

“If you have a dynamically calculated VSWR reading available, it can be used to spot changes before operations are affected, for instance to automatically turn on antenna deicing equipment.”

He said that other broadcast plant monitoring and control capabilities now include the tracking of vacuum tube lifetimes, keeping tabs on nitrogen generator run times to flag the presence of leaks that might have developed in pressurized transmission lines and waveguides, tracking operation times of backup AC generators for scheduling maintenance, and the like.

PUTTING THEM ALL TOGETHER

Dan Fallon

Dan Fallon

Dan Fallon, Dielectric’s senior RF engineer, provided a very deep dig into what goes into a common transmitting antenna for multiple FM stations, as well as the best way to construct one.

He described a recent project that involved constructing an antenna/combiner system for use in Lima, Peru, which accommodated eight FM stations, noting that the design had been previously used for multistation operations in St. Louis and Jacksonville in the United States.

“It provides very high isolation — better than 30 dB between 88 and 108 MHz,” said Fallon. He noted that a critical element in any high-power multistation antenna project was in keeping intermodulation products as low as possible.

“If the intermod is high enough, it will interfere with our neighbors in the FM band and can also interfere with airport and other communications.”

Fallon also described the way to achieve circular polarization in multiuser antennas of this type, and also explained combiner engineering, enumerating the pros and cons of using constant impedance filter (CIF) or manifold combiner designs. He also explained advantages of using cross-coupled filters over Chebyshev designs.

FM INTERFERENCE ISSUES AGAIN

Even though it was the last item on the 2018 symposium program, there was certainly no lack of interest or loss of audience for the “FM Translators and Interference” panel discussion that featured Educational Media Foundation’s Sam Wallington, Beasley Broadcasting’s Mike Cooney, and the FCC’s Martin Doczkat.

After Doczkat set the stage with an overview of pertinent regulations and a primer on VHF radio propagation, the discussion then shifted to the situation that exists with translators today, with Wallington offering a statistic that could well account for interference problems.

“Today, translators outnumber full-power stations,” he said, noting that the most recent listing shows some 7,848 translators on the air versus 6,737 full-power FM stations.

Panel members seemed to agree that the most contentious item is the current 54 dBU protection contour.

“We can agree on everything except the 54 dB contour,” said Cooney, adding that “most of us who bought translators knew they were a nonprotected service. We really didn’t want a protected contour.”

Wallington observed that “contours have the challenge of being less accurate when you get past 16 kilometers [app. 10 miles] because of the terrain. I don’t believe the 54 dBU F(50,50) contour is the right thing.”

He added that “translators are risky; pay accordingly.” He also stressed industry cooperation for resolving interference issues at the grass roots level.

“I’d rather spend money on engineers than lawyers,” he said. “Call me if there’s a problem. I can get that translator off my channel quicker and cheaper than if I have to fight it in court.”

The 2019 IEEE BTS Symposium will be held Oct. 1–3, 2019, at the Hartford Marriott Downtown hotel in Hartford, Conn.

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