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Narrowbanding Overview

Narrowbanding refers to public safety and industrial/business land mobile radio systems migrating from 25 kHz efficiency technology to at least 12.5 kHz efficiency technology. Narrowbanding is also referred to as VHF/UHF narrowbanding because the frequency bands impacted by narrowbanding are in the VHF/UHF ranges.

There is a separate help article on how to file a narrowbanding application.

What is the purpose of narrowbanding?

The 150-174 MHz and 421-512 MHz frequency bands are congested with limited frequency availability for implementation of new systems or expansion of existing systems. Narrowbanding to at least 12.5 kHz efficiency technology will enable licensees to operate more efficiently, either with narrower channel bandwidths or an increased number of voice paths or higher data rate per channel.

Who has to narrowband?

As of January 1, 2013, all public safety and industrial/business land mobile radio systems operating in the 150-174 MHz and 421-470 MHz bands were required to cease using 25 kHz efficiency technology and begin using at least 12.5 kHz efficiency technology.

Note: The narrowbanding requirement also applies to the 470-512 MHz bands. These frequencies are sometimes referred to as the T-Band. However, on April 26, 2012, the January 1, 2013, deadline was waived while the Commission considers issues surrounding future use of the T-Band. Additional information about the waiver is available in an order.

As of April 1, 2014, PSHSB will dismiss applications to renew 150-174 MHz and 421-470 MHz band wideband-only licenses unless: (a) the application also proposes to modify the license by replacing the wideband emission designator(s) with narrowband emission designator(s); or (b) the application certifies that the station equipment meets the narrowband efficiency standard.

What does equivalent efficiency mean?

Any of the following meet the 12.5 kHz equivalent efficiency requirement:

  • One voice path in a 12.5 kHz channel;
  • Two voice paths in a 25 kHz channel; or
  • Data operations on channels greater than 12.5 kHz must employ data rates greater than 4.8 kbps per 6.25 kHz channel, such as 19.2 kbps per 25 kHz channel.
How do I know if I need to comply with the narrowbanding requirement?

There are three steps:

  1. Check the radio service code on your FCC license. Only radio service codes IG, IK, PW, YG, YK, and YW are part of the narrowbanding requirement.
  2. Check the frequencies on your license. Frequencies between 150-174 MHz or 421-470 MHz are part of the narrowbanding requirement.

    Note: The following paging frequencies are exempt from narrowbanding:

    • 152.0075 and 157.4500 MHz in the Public Safety Pool (note: frequency 163.250 kHz is NOT exempt from narrowbanding); and
    • 152.480, 157.740, 158.460, 462.750, 462.775, 462.800, 462.825, 462.850, 462.875, 462.900, 462.925, and 465.000 MHz in the Business Industrial Pool.
  3. Check the emission designator of the frequencies that are part of the narrowbanding requirement. An emission designator with a bandwidth of 11.25 kHz (11K3) or narrower complies with the narrowbanding requirement.

    Note: If you are required to narrowband, you need to file an application in the FCC’s Universal Licensing System (ULS). There is a help article that provides information on filing a narrowbanding application.

How do I check for the information in the three steps above?

You can use the FCC’s Universal Licensing System (ULS) license search. The quickest way is to search by your call sign.

Once you enter your call sign and select Search, the radio service code is listed on the next screen.

To view the frequencies and emission designators, select the Call Sign, and then select the Frequencies tab towards the top of the screen. Once you are at the Frequencies screen, select the Emission link towards the top of the screen. The frequencies and emission designators are listed.

Can you explain the format of the emission designator?

The emission designator is made up of 7 characters. For purposes of determining whether narrowbanding is required, you need to focus on the first four characters. These characters determine the bandwidth.

The bandwidth will always include three numerals and one letter. The letter is the position of the decimal point and represents the unit of bandwidth. The bandwidth unit designator can be H = Hz; K = kHz; M = MHz; or G = GHz.

The emission designators where narrowbanding applies should always include a K for kHz.

Here is an example of an emission designator that complies with the narrowbanding requirement: 11K2F3E. This emission designator complies because it is 11.2 kHz (listed as 11K2).

Here is an example of an emission designator where narrowbanding needs to happen: 20K0F3E. This emission designator does not comply because it is 20.0 kHz (listed as 20K0).


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