TV and radio stations are finding it difficult to upgrade or replace older VHF/UHF part 74 remote pickup (RPU) radios used for coordinating news operations, live audio feeds and IFB. While the FCC has been encouraging public safety and commercial two-way radio users to move to narrow-band digital technology, digital emissions (except, one could argue, telemetry and command on the narrow "P" channels at each end of the 450/455 MHz bands) are not allowed under Part 74 on the VHF/UHF RPU bands. Stations wanting to use analog FM are finding they have to stack an odd-number of existing Part 74 center channel frequencies to obtain a center frequency that the Commission will approve, and one that is programmable on most modern radios. This means that to obtain a usable 25 kHz wide channel, the applicant has to file for five stacked 6.25 kHz channels, or 31.25 kHz, wasting 6.25 kHz of bandwidth.
And in markets such as New York and Los Angeles, where a large number of radio and TV stations are sharing RPU bands, spectrum is too scarce to waste.
The Society of Broadcast Engineers (SBE) has offered a solution. It has filed a Petition for Rule Making that would change the channel spacing in the 450 to 455 MHz band to 3.125 kHz, and the channel spacing in the RPU bands between 150-162 MHz to 3.75 kHz. Section 74.462(a) of the FCC rules would be modified to state that any form of modulation could be used.
Section 74.462(b) is a table listing allowable bandwidths. Section 74.462(c) sets rules for emission mask and transient frequency behavior. It references Section 90.210 and 90.214 of the rules for bandwidths up to 30 kHz with a separate schedule for all other emissions.
Recognizing the amount of time it takes for a rule making to become law, the SBE also filed a Request for Temporary Waiver of Section 74.462 of the Commission's Rules to Permit Licensees of Remote Pickup Broadcast Auxiliary Stations to Utilize Digital Radio Telephony and Data Emissions. The filing does not request a change in the Part 74 center frequencies.
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.
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