Many high-power broadcast stations have few options for staying on the air while replacing a transmitter. Acrodyne Services, focused on transmitter installation and service, has developed the Mobile Acrodyne Transmitter (MAT) — a self-contained UHF transmitter housed in an enclosed trailer.
As an external system, MAT maintains broadcasting without interfering with the removal of the old transmission system, room prep, electrical modifications, and new transmitter installation inside the facility. MAT can broadcast ATSC 1.0 or ATSC 3.0 signals.
“Stations and TV groups are continuing to upgrade their broadcast infrastructures by replacing old transmitters,” Acrodyne GM Andy Whiteside said. “There are low-power solutions and other workarounds, but none of them are ideal, especially for stations that have limited space or run into unexpected delays because of logistic and structural issues. MAT provides a clean, external, and high-power solution that allows broadcasters to conduct business as usual.”
Whiteside added that the UHF version has been deployed successfully several times, and a VHF version is currently being prepared for deployment later in 2021.
Dale Scherbring, Director of Engineering for RF transmission at Sinclair Broadcast Group, described MAT as a “full-power transmitter on wheels that was designed by Acrodyne engineers who get their hands dirty.”
The climate-controlled trailer features a one-rack, liquid-cooled Rohde & Schwarz THU9evo UHF19kW transmitter with 12 amplifiers, Dielectric tunable mask filter, patch-panel, test load plus pumps, and separate heat exchangers for the transmitter and test load. Stations only need to provide AC power and an input signal from master control. Acrodyne provides a run of coaxial flex line to connect MAT’s output to the antenna to maintain regular broadcasting.
Sinclair Broadcast Group Manager of TV Transmission Engineering Rusty Mooney was part of MAT’s initial deployment in June 2020 at the company’s two stations serving Raleigh: WLFL-TV and WRDC-TV. Both transmitters were in the same room and both needed to be replaced. Plus, a new filter for WRDC needed to be installed. “There just wasn’t enough room for all of that work,” Mooney recalled. “You’d run out of wall space trying to keep one transmitter running while trying to build a new transmitter.”
With MAT parked outside the facility and transmitting, the old WRDC transmitter was removed – and when the new WRDC transmitter was commissioned, MAT was quickly reconfigured to broadcast for WLFL while its transmitter was replaced. “MAT allows you to offload your signal to the trailer,” Mooney said. “Then you can gut the room and start with a clean slate for the new install.”
MAT’s next stop was KDNL-TV, a Sinclair station serving St. Louis, in early January 2021. According to Mooney, the small RF facility required extensive renovations in addition to a new transmitter. The station stayed on the air until late March with MAT while it replaced its two-cabinet IOT transmitter.
Acrodyne’s “transmitter on wheels” concept was first developed during the recent FCC Repack, when hundreds of UHF stations across the country transitioned to new channels. Last September, WHKY, an independent station owned by Long Communications that serves part of the Charlotte market, rented an earlier version of MAT while renovating its facility and replacing its old transmitter.
Between the four-cabinet transmitter and two very large filters for the channel 14 UHF station, the building did not have room to accommodate a second transmitter. “I had to get the old transmitter out of the building,” said Tom Long, one of the station owners. “MAT makes it a lot easier. It got everything out of my way and it’s self-contained.”
Once all its Repack projects are complete, Sinclair is expected to replace the remaining IOT transmitters in about 20 of its stations with solid-state transmitters. Scherbring expects to use MAT at those locations and at the VHF-to-UHF conversions currently being considered. However, he said MAT can also be deployed for emergency or disaster situations, and the system can be operational within a day. Both VHF and UHF versions of MAT will be available for use by all broadcasters, subject to demand.
