Retrofitting the C-Band Downlinks: A Daunting Task
ALEXANDRIA, Va.—While the FCC could wave its wand and turn all C-band downlinks into just so much scrap metal, optimism runs high that the CBA’s proposal for reapportionment of the 500 MHz spectrum and band sharing will be the outcome—if 5G does have to be accommodated.
However, that approach involves the addition of an LNB filter, and likely will require retuning receivers and moving dishes to different satellites. This sounds easy enough, but when you consider that upwards of 14,500 downlink sites are involved, and that many of these have multiple antennas—some as many as a dozen—the effort becomes rather mind-boggling.
In its proposal, the CBA estimates that the necessary work could be completed in “a period of only 18 to 36 months from the time of a final FCC order.” However, based on his long experience with earth stations, John Joslin, director of sales and marketing for satellite vendor Dawnco, is somewhat skeptical.
“Under good conditions [ground-mounted antennas], it should take 20 to 40 minutes to install one filter, and perhaps an hour to install four,” he said. “Under worst-case scenarios such as mountaintop downlinks, rooftop installations, or high-security locations, it could take much longer.”
He estimates—again under optimum conditions—that once filters are in place, it will then take another 20 minutes to an hour to retune a facility’s sat receivers.
The real time-sink may be the requirement for repointing and peaking dishes for optimal performance if it’s necessary to change satellites to replicate services.
“The average 3.7-meter satellite antenna can take two to four hours to reposition,” he said.
He cautioned, however, that many downlinks suffer from neglect, and most antennas used for day-in-day-out reception of a program service by broadcasters are fixed, not motorized, and as such can be literally “frozen” in place.
“Many older dishes have rusted bolts that will take a great deal of time and effort to loosen or cut off and replace,” he said. “C-band dishes larger than seven meters will be very hard to repoint because of the need for special tools and hoists. Dishes smaller than three meters are very difficult to use, and sometimes can’t be peaked for proper reception when used with new ‘finicky’ digital satellite receivers.”
Joslin says, based on experience, it’s likely that a small percentage of sites will need a total dish replacement, and this could take days or weeks.
WHAT’S THE BEST WAY?
While one approach would be to establish a “logistics support” operation, with teams sent out to make the earth station changes, Joslin doesn’t really think this is realistic, given the short period of time proposed for the changeouts, the very large number of sites involved, and many variables that may be encountered.
“I just don’t see it happening this way,” he said. “At least not in a relatively short amount of time. There are just too many things to go wrong—scheduling downtime to take a dish off line, getting access to remote sites, or especially antennas in a secure are.
“And in many situations, you’re going to find dish owners who are protective about their installations and are not going to want someone else to come in and make changes without their people there to oversee things,” Joslin added. “All this is going to require a lot of planning and scheduling, adding to the time to do the changes.”
If the CBA proposal is approved, Joslin believes that C-band dish owners would be happier—and the changeouts would go faster if a program were set up similar to that in place with the ongoing TV spectrum repack, with owners being responsible for securing their own equipment and installers, and reimbursement coming from the FCC.
“I’ve spoken with a number of my customers and the majority favor such an approach,” he said.
LESSONS LEARNED IN A REAL-WORLD SCENARIO
Bob Kovacs, former technology editor for TV Technology, also worked as a Sprint broadcast engineer during that company’s initiative to replace TV station analog microwave ENG gear with newer digital models to free up 2 gHz spectrum, shared his thoughts about the logistics of any sort of large-scale facility modification. While he acknowledged that adding filters, retuning receivers and repointing satellite dishes might be less demanding than changing out microwave gear, the number of sites involved in the Sprint project (about 1,000) amounts to only a very small fraction of the downlinks that will need attention, he doesn’t really see an outcome any better than that achieved with the Sprint initiative. (It ran almost twice as long as originally projected.)
“The BAS Relocation project started in 2004 and was officially complete in July 2010,” said Kovacs. “When I was hired in 2005, I was told that the project was expected to be completed by September 2007. However, things got bogged down due to various unplanned issues and it took nearly three years longer to complete than initially planned.”
Kovacs said some of the delays occurred in connection with sites that had received no attention in years and required time in excess of that budgeted. Other slowdowns were due to outdated or otherwise inaccurate station equipment inventories that had to be reconciled. There were also a number of other issues, including the inability of suppliers to deliver sufficient gear within the necessary time frame.
“What looked good on paper didn’t always pan out in the field,” he said.
Kovacs added that one of the more daunting—and sometimes time-consuming—tasks in connection with the analog/digital swap was to convince TV station personnel that their day-to-day operations would not be impacted by replacement of the old gear with new.
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James E. O’Neal has more than 50 years of experience in the broadcast arena, serving for nearly 37 years as a television broadcast engineer and, following his retirement from that field in 2005, moving into journalism as technology editor for TV Technology for almost the next decade. He continues to provide content for this publication, as well as sister publication Radio World, and others. He authored the chapter on HF shortwave radio for the 11th Edition of the NAB Engineering Handbook, and serves as editor-in-chief of the IEEE’s Broadcast Technology publication, and as associate editor of the SMPTE Motion Imaging Journal. He is a SMPTE Life Fellow, and a Life Member of the IEEE and the SBE.