Midwest Television announced this week to enthusiasts on the HDTV.forSanDiego.com forum that KFMB-DT will broadcast digital TV on channel 7 beginning in March. The station will give up channel 55, the spectrum it has used since 2001, to MediaFLO, a Qualcomm division that transmits mobile multichannel television and has purchased from the FCC the rights to use channel 55 nationwide.
In order to temporarily occupy channel 7 VHF, Qualcomm worked with KFMB, incumbent NTSC channel user KABC in Los Angeles, and the FCC. They were able to obtain an experimental license for a period that will expire February 17, 2009, when KFMB-DT will occupy only its elected channel 8 with an ATSC signal. The experimental license will require two renewals since they are granted on a 6-month basis.
According to Rick Bosscher, KFMB RF Supervisor, the complicated agreement between these parties includes some protection for KABC. The KFMB VHF 16-panel Delta Wing array antenna made by Dielectric beams in a cardioid pattern with a sharp null in the direction of KABC’s line-of-sight Mt. Wilson transmission antenna. KFMB-DT 7 will initially sign on with only 47 kW ERP from a new Harris CD Platinum VHF transmitter. After they retire the Comark channel 55 transmitter, they will install additional PA cabinets to bring the ERP to 140 kW maximum from the easterly lobe. When they move to channel 8 next year, the antenna will be rotated to place the null toward the ocean, and used only as a standby. They will use the older top-mounted omni-directional slot antenna as primary. At that time, power will settle at 14.9 kW ERP.
In order to support the VHF panels, the 1954 vintage tower had to be substantially reinforced, and new one-inch guy wires installed to the top. Travis Donahue of Wireless Infrastructure says their company may have “put up more steel than made up the original tower.”
As part of the deal, KFMB Stations Director of Engineering Rich Lochmann says they will provide space for MediaFLO channel 55 transmissions on a neighboring tower at their Mt. Soledad site.
Additionally, Rich says, LG/Zenith will use the new VHF ATSC station to test their new set-top boxes in the San Diego County terrain.
When the February Nielsen ratings sweep is finished February 28, the station will publicize the transition for digital viewers, then, if all goes well, the switch will take place March 6.
The added transmitter required substantial electrical power planning and rework, and Bosscher says Juice Electric did a great job supplying the power while everything stayed on the air.
The experimental permit for the project raised some eyebrows among technical observers. It’s not publicly known whether the permit was coordinated with Mexico. Temporary, scheduled use of spectrum operating outside parameters of standard FCC rules traditionally involves a Special Temporary Authority permit issued by the FCC’s Media Bureau rather than an Experimental Permit issued by the Office of Engineering and Technology (OET). Details of the permit were not published on the internet but were available by visiting the OET in person. MediaFLO has obtained numerous experimental permits to broadcast its mobile television in the San Diego area during its product development phase.
The author of this article, Gary Stigall, is Director of Engineering for Bay City Television, dba XETV FOX6, owned by Mexican broadcaster Televisa Corporation. He previously worked for KFMB Stations for 13 years.