Mandatory 6.25 kHz VHF/UHF Narrowbanding? Not Soon!


A recent FCC decision resulted in some riled up members of the Part 90 land mobile radio community.  Specifically, on July 30 the FCC denied a Waiver Request submitted by the International Municipal Signal Association (IMSA).   IMSA had requested that the FCC waive the requirement that Part 90 VHF & UHF radio manufacturers include a 6.25 kHz bandwidth mode (or equivalent efficiency) into newly type-accepted products.

Thus, the Commission’s 1995 decision to require that manufacturers include a 6.25 kHz bandwidth mode (or equivalent efficiency) into all VHF/UHF Part 90 equipment type accepted after January 1, 2013 remains in place.  While manufacturers may continue to manufacture equipment type accepted before January 1, 2013 (i.e. 12.5 kHz only), availability of such new equipment is sparse.

While the Commission denied the Waiver Request, the Order did include the following statement:

“The Commission has stated repeatedly that the migration to 12.5 kilohertz operation was only a transitional step in the eventual migration to 6.25 kilohertz technology, and that it intends, if necessary, to establish a deadline for mandatory migration to 6.25
kilohertz technology.”

This statement caused a few folks to express concern that there would be another mandatory change in equipment coming soon.  However, mandatory Part 90 VHF & UHF narrrowbanding to 6.25 kHz (or equivalent efficiency) won’t be happening for a long time.  If this is sufficient to ease your personal concerns, feel free to stop reading this post now.  But, if you want to see why, please read on.

The background on what has come to be called narrowbanding is long and complicated. However, it’s important in the consideration of the next level of spectrum efficiency.

In 1987, I filed a Petition for Rule Making on behalf of the National Association of Business and Educational Radio (NABER, now WIA), asking that the FCC permit the trunking of what was then the 800 MHz “Conventional Pool” frequencies.  In response, the FCC issued a Notice of Inquiry (PR Docket No. 87-213, 2 FCC Rcd 3820, released June 29, 1987) that not only proposed to look into 800 MHz trunking, but also whether the VHF and UHF bands could utilize trunking technology to achieve greater efficiency.

We recognized that VHF/UHF “refarming” would be quite the regulatory quagmire, while the 800 MHz issue was fairly simple.  Therefore, we successfully convinced the FCC to tackle the VHF/UHF issue in a separate proceeding.  As a result, there were two different proceeding, with 800 MHz trunking dealt with in a 1988 Notice of Proposed Rule Making.

What became VHF/UHF narrowbanding was handled in PR Docket No. 92-235.  Along with other rule changes in the bands, the FCC initially established a transition time to move from 25 kHz bandwidth equipment to 12.5 kHz bandwidth equipment in a 1995 Report And Order And Further Notice Of Proposed Rule Making.  In that decision, the FCC decided to manage narrowbanding of these bands through the equipment type acceptance process, over a ten year period.

Note the time frame – seven years between the NPRM and the Report and Order.

Subsequently, the Commission did not believe that the pace at which 12.5 kHz (or equivalent efficiency) equipment was being adopted by the land mobile radio industry.  Therefore, in 2003 the Commission issued a Second Report and Order, which initially created a deadline for 12.5 kHz migration of January 1, 2013 for non-public safety systems, and January 1, 2018 for public safety systems.  Subsequently, the Commission decided to make the dates the same for both types of users, January 1, 2013.

Again, note the time frame – ten years for migration.  When the non-public safety land mobile radio industry asked for that to be shortened, the Commission refused.

To go to mandatory 6.25 kHz bandwidth (or equivalent efficiency), the Commission will again need to go through another rule making proceeding.  Given: (1) how long the initial rule making took to get to completion (seven years); (2) how difficult the mandatory 25 to 12.5 kHz conversion was for the Commission; (3) the fact that another rule making on this issues is not presently on the FCC’s radar (note in the IMSA decision the words “if necessary” were used); (4) the time-line for conversion (ten years); and (5) the “rapidity” that current Part 90 items are flowing out of the Commission, is there any reasonable expectation that mandatory 6.25 kHz migration will happen before virtually every piece of 12.5 kHz only equipment is gone?


One thought on “Mandatory 6.25 kHz VHF/UHF Narrowbanding? Not Soon!

  1. The commission is going amuck letting Cellular push broadcasters out .
    Then closing field offices which leaves unlicensed operations , interference issues unresolved .
    They should have fixed the VHF spectrum aligning input and outputs like the UHF and 800 MHZ bands are !
    The t-band issue is looming
    Talk about messed up decisions – looks like they are going out of Business – maybe Amazon could do better !


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