Stations Need to Protect Wireless Mic Use
While wireless microphones need to be licensed in order to get the most protection from white space device interference, just having a license does not provide protection from white space devices. Most low-power auxiliary licenses specify operation throughout the entire TV band to give licensees the option of changing channels to avoid interference. However, before a wireless microphone (licensed or unlicensed) can be registered in the white spaces database for protection, certain criteria have to be met,
Protection is based on database registration of the location and time, along with the frequency the mic uses. This makes it impossible to register wireless microphones used in the field for newsgathering unless it's for a specific event such as election night coverage at campaign headquarters. The same rules apply to wireless mics used for sporting events—you can't register 24 hour-a-day use at a stadium. Devise use during specific times for games can be registered. Sites and venues where unlicensed wireless microphones, or other low power auxiliary service devices, are used have to be registered at least 30 days in advance. This is to give the FCC time to make requests for registration available to the public and to provide an opportunity for public comment.
Registration of channels available for white space devices at events or venues is available only as a last resort. The rules state, "Parties responsible for eligible event venues filing registration requests must certify that they are making use of all TV channels not available to TV bands devices and on which wireless microphones can practicably be used, including channels 7-51 (except channel 37)."
Registrations must include the name of the owner of the low power auxiliary device (not the licensee), a contact person, address, e-mail, and phone number, and coordinates where the devices are to be used (latitude and longitude in NAD83 accurate to 50 meters). The registration for each site must also include the channels used by the low power auxiliary service devices to be operated, and the number of wireless microphones used on each channel. According to the rules:
"As a benchmark, at least 6 – 8 wireless microphones must be used in each channel. Registration requests that do not meet these criteria will not be registered in the TV bands data bases."
The registration requests must include the specific months, weeks, days of the week and times that the devices are to be used. Registrations for licensed devices need to include the call signs of the wireless microphones or low power devices. Registrations for unlicensed devices must also include the name of the venue where they will be used.
Here are some steps stations can take to reduce the chances of interference:
First, make sure all microphones are licensed. Wherever possible, license the mics on broadcast auxiliary frequencies outside of the TV bands, such as 944-952 MHz, after appropriate coordination is done to avoid interference to aural STL links and other broadcast users. If frequencies in the TV bands are used, make sure the mics the crews are using operate on one of the two channels reserved for wireless microphone use (the first available channels above and below channel 37). The FCC Order recommends using frequencies below channel 21, where portable white space devices are not permitted,
With fewer channels available for ENG wireless microphone use, coordination between stations will be necessary to avoid interference. The FCC Oder states, "We also observe that in the case of a major unplanned news event, broadcasters already coordinate their use of frequencies for wireless microphones and that at a site can share frequencies by avoiding operation of wireless microphones at the same time."
For known large events, such as election night coverage, consider registering additional channels if needed.
It should be possible to register licensed low-power auxiliary device operations in production studios, once it's been demonstrated that alternative frequencies are not available. Note, however, that the specific times the devices in the studio must be listed in the registration and that the FCC will take action—including denial of registration—if it finds frequencies and times are being registered, but not used.
Finally, check the registration database to be sure operations are correctly listed. Note that personal/portable white space devices are allowed to operate for up to 48 hours without updating their list of available frequencies, so plan ahead.
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Doug Lung is one of America's foremost authorities on broadcast RF technology. He has been with NBC since 1985 and is currently vice president of broadcast technology for NBC/Telemundo stations.