Channel 14 Interference

In the process of “repacking” television broadcast stations to make room for additional wireless services, the Federal Communications Commission (FCC) has assigned Channel 14 (470-476 MHz) to TV stations in 21 markets around the country. The potential for interference from Channel 14 to Land Mobile Radio (LMR) spectrum below 470 MHz has long been recognized, and FCC rules require TV permittees on CH 14 to “submit evidence that no interference is being caused [to LMR systems] before it will be permitted to transmit programming….” The rules state that the TV permittee “must reduce its emissions within the land mobile channel. . . that is receiving interference caused by the TV emission producing a vertically polarized signal and a field strength in excess of 17 dBu at the land mobile receiver site.”   
 
LMR licensees in markets such as New York City; San Francisco; Lansing, Michigan; and Jacksonville, Florida have been contacted by Channel 14 permittees to participate in testing for interference. Although the broadcast community seems to assume that only frequencies from 468 MHz and up are likely to be affected, destructive interference sufficient to prevent a system from being keyed up has been detected as far down as 461 MHz in one instance when the broadcast and LMR sites are separated by only one mile. It is unclear whether broadcaster-funded filtering at either or both the broadcast transmitter and LMR receivers will alleviate the problem. Locating alternative spectrum for either the TV or LMR systems is, at the least, problematic. It seems inevitable that FCC involvement will be needed to resolve some situations. EWA is presently considering participatory options. 
 
In certain markets such as Green Bay, Wisconsin; Syracuse, New York; and Louisville, Kentucky, the Channel 14 permittees undertook substantial efforts to protect LMR systems from interference and seemingly have been successful. 
 
The FCC transition schedule is a 10-phase process that continues until July of 2020. The transition schedule includes a protracted period for testing to identify and resolve interference.  
 
If you or a client is in an affected area, 
1. Make certain that the broadcaster is aware of the presence of the LMR system by responding to correspondence from Engineering firms. 
2. Work closely with the TV broadcaster to ensure that the affected system is protected from interference.
3. Share with EWA letters that you receive from a broadcaster or surrogates, such as engineering firms. Please send communications to Andrea Cumpston.  
Category: EWA On Your Side