A step toward digital STL

It has taken four years, but broadcast stations apparently may get long-awaited FCC approval to begin using digital microwave studio-to-transmitter links (STLs) without the need for special temporary authority (STA) every six months or a waiver.

"Broadcasters need to convert their studio-to-transmitter links to digital or hybrid analog-digital if they're going to carry a high-definition signal," says Dr. Dane Ericksen, chairman of the FCC Liaison Committee of the Society of Broadcast Engineers (SBE). "The FCC is choosing to interpret its rules to allow digital modulation only in the 18 GHz band, which very few broadcasters use for STLs."

Most TV stations use the 7 and 13 GHz bands for STLs, but current rules say that digital modulation is allowed only at 6.5 and 18 GHz. Unfortunately, the 6.5 GHz link is not suitable for STL, and 18 GHz is for short haul, nothing more than 10 miles. According to Ericksen, the FCC has interpreted the broadcast auxiliary rule, which relates to 6.5 and 18 GHz, to mean that digital modulation is prohibited in all the other microwave bands.

Ericksen says that there isn't a problem with digital modulation in the other bands; the limitation was simply a result of rulemaking being concerned only with the shared bands. The FCC has continued to limit digital microwave transmission to those two bands. The result for broadcasters looking to send digital signals to their transmitters via digital STLs is that, every six months, they need to request an STA to use the digital or hybrid STL.

The issue is not a new one. In March 1998, the Telecommunications Industry Association/Electronics Industry Association filed a petition for a rulemaking that proposed to amend the FCC rules to allow digital modulation in any of the TV microwave bands. "It's more than four years later," says Ericksen, "and what should have been a trivial issue handled by a public notice still has broadcasters jumping through hoops.

He adds the hardware has been available to do digital and hybrid STLs for two years, but the problem is that broadcasters need either a waiver or an STA. "On one hand, the FCC says it doesn't have enough people to process the applications it gets. On the other, it requires an STA, which requires a separate filing and separate fee," he says. "The only word for this is 'silly.'"

Ericksen estimates that about 300 of the stations on the air with DTV signals are operating under STAs because some use fiber optic or have the transmitter co-located with the station. And, while the $150 fee isn't going to cause headaches, it's too easy to forget to renew and face a potential $10,000 penalty for having an unauthorized microwave link.

The belief now is that the report and order will make it to FCC commissioner levels in June. "The best thing that could happen is the commissioners realize this is not controversial, they sign off on it, and it gets published in the Federal Register," says Ericksen. "Sometimes, that last step could take months so SBE has urged that the report and order include an 'effective upon adoption' clause."

"Hopefully, we're seeing light at the end of the tunnel," he says, "and this will be the last round of STAs that stations will have to do."