Photo Doug Wilson

Q: Do we need to purchase all new equipment, or can we reprogram our radios to meet the narrowband requirements?
A: With all the products available on the public safety communications market, it’s difficult to tell which ones are narrowband compliant. So we invited two-way radio manufacturers to identify which of their mobile and portable radio models, and base stations are compliant. Posted online, this list can serve as a guide, but verify the compatibility of your radios with each manufacturer. Test equipment is also available. The companies represented in our listing are:

• Aeroflex Inc.;
• EF Johnson;
• Harris Corp.;
• Icom America;
• Kenwood USA;
• Motorola;
• RELM Wireless;
• Tait Radio Communications;
• Thales Communications; and
• Vertex Standard.

Q: Will narrowbanding reduce our coverage?
A: The short answer is yes, it’s very possible. The FCC reports that narrowband compliance can result in a 3 dB loss in signal strength. However, this is based on a simple narrowbanding scenario in which a 25 kHz analog system converts to a 12.5 kHz analog system.

Why the reduced coverage? Your transmitter deviation will be reduced by half. Your “voice power” will be reduced. Your radio receiver, which can’t be narrowbanded, will still be expecting to receive a signal at full deviation. What will fill this newly created empty space? Noise. Noise from power lines, spark plugs, electronic cash registers, atmospherics and distant stations. Your voice signal is now competing with all of these other sources for your radio’s attention. Your receiver will have a hard time separating your voice from all of this noise. Thus, you will experience reduced coverage. In some areas, this reduction could be significant.

Make sure you perform your due diligence when evaluating any potential or actual performance impairment. Planning should include voice testing and the reliable decoding of alert paging. Several options exist for range recovery, including compandoring and noise blanking.

Compandoring is a method in which the transmitted audio is compressed before going into the transmitter, then expanded at the receiver. The result attempts to recover much of the intelligibility. Sometimes, however, sounds below a threshold level may be weak, while those above may boom through.

Noise blanking is a method in which a circuit in the receiver detects the fading and blanks the receiver during the fading period to make it sound quieter. Neither technology is new; both have been used in analog wireless communications, as well as broadcast radio, for decades and may have advantages if there is only one type of transceiver being used systemwide.

Compandoring techniques vary. Enabling compandoring on A-brand and B-brand radios creates the potential for distortion, making speech even more difficult to hear. There’s no apparent interoperability between compandoring schemes, and at least one mutual aid plan recommends analog operation without compandoring enabled so communication between different manufacturers’ radios is possible.

Also see “Narrowbanding: The Tech Side” for tips on restoring system receiver performance.

Q: Are we required to go digital or adopt Project 25 (P25)?
A: No, there’s no requirement for public safety agencies to go digital or adopt P25. Licensees can operate in either analog or digital formats as long as they operate at 12.5 kHz efficiency. However, there are benefits to going digital. (See “Narrow It Down: Analog vs. Digital Radio Systems,” March 2011 PSC.)

Q: After we narrowband, will we realize two frequencies from the migration?
A: No. You are reducing the emission of the current frequency, not dividing the frequency you’re using into two separate 12.5 kHz channels. You will need to justify and apply for additional 12.5 kHz channels through a certified frequency coordinator.

Q: What does equivalent efficiency mean?
A: 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; and
• 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.

Q: Will the FCC really enforce the Jan. 1, 2013, deadline?
A: The FCC states on its website that “Non-compliance will be considered a violation that could lead to FCC enforcement action, which may include admonishment, monetary fines, or loss of license.”

FCC Public Safety & Homeland Security Bureau Chief Admiral Jamie Barnett (Ret.) has previously indicated to Public Safety Communications that the FCC has no plans to extend the Jan. 1, 2013, deadline because public safety has long had access to the equipment. Adm. Barnett said, “[This] has been going for 10 years, and the equipment has been available for longer than that. … It’s been a process that certainly people could see coming. So while [the economics of obtaining replacement equipment is] of concern to us—and anybody can petition for a waiver—I think it’s going to be judged in the broad view of what their specific situation is. They can give the facts that are affecting them, and that will be weighed against the fact that it affects other people and that they’ve had some significant time to prepare for it.”

Q: Has the FCC established a schedule for mandatory migration to 6.25 kHz efficiency?
A: No. The FCC has not set a date by which licensees must operate in 6.25 kHz efficiency. The only requirement is for users to migrate to 12.5 kHz efficiency by Jan. 1, 2013. PSC

Answers compiled from articles in Public Safety Communications by Steve Makky Sr., Charles Taylor and Ralph Gould, as well as from the FCC’s narrowbanding website at http://transition.fcc.gov/pshs/public-safety-spectrum/narrowbanding.html.

Originally published July 2011 in Narrowband Now: Strategies for Meeting the Jan. 1, 2013, Deadline, a supplement to APCO International’s Public Safety Communications sponsored by Aeroflex Inc., Kenwood USA Corp., Motorola and Simulcast Solutions LLC.

Related Stories

• “On Your Watch: Like It or Not, Narrowbanding Is Just Around the Corner,” by Ron Haraseth
• “Check Your License: Operating a Radio with an Expired  License Can Get You Fined or Knocked Off the Air,” by Chris Kindelspire
• “‘Unfunded Mandate’: How to Fund Your Narrowbanding Project,” by Charles Taylor & Keri Losavio
• “Narrowband Migration: Lessons Learned & Best Practices,” by Keri Losavio, with additional reporting by Teresa McCallion