Narrowbanding FAQs: FCC Official Answers Technical Narrowbanding Questions
Wednesday, January 20, 2010 | Comments
Editor’s Note: MissionCritical Communications received several technical questions from readers referencing the Jan. 6 “Narrowbanding: Helpful Tips from Spokane” article. Following are answers from Ira Keltz, deputy chief of the FCC’s Office of Engineering and Technology.
 
In addition, FCC officials have agreed to answer technical questions submitted by MissionCritical Communications readers. If you have a technical question regarding VHF or UHF narrowbanding, e-mail editor@RRMediaGroup.com, and we will request an answer from the FCC and run the information as soon as possible.
 
Question 1: If a licensee uses a narrowbanding modification kit from a third-party manufacturer, do the kits need to be type accepted by the FCC? The referenced article above describes the modification kits: We have a lot of GE MASTR II repeaters and voted receivers, which aren’t narrowband capable. Communications Specialists, a company in California, makes numerous modification kits for various makes and models of base radios. The kit for the MASTR IIs includes new crystal filters and a capacitor, which converts it to narrowband. In bench tests before and after the modification installation, we gained 1 to 1.5 dB of quieting on the SINAD.
 
Answer: Based on this description, the kits would not need FCC approval because they consist of a set of passive components. However, using these kits to modify the radio entails a hardware modification in the operator’s repair shop, which requires a new equipment certification and a new FCC ID (See 2.1043(a)).
 
Question 2: Can a licensee, using commercial, off-the-shelf test equipment bring a transmitter into acceptable limits of the emission mask for 11K2F3E by realigning the deviation from the current 5 kilohertz down to the new 2.5 kilohertz? For example, a licensee has new, narrowband-capable radios that he has switched to narrowband to use as a reference. After realigning a transmitter to produce only a 2.5-kilohertz deviation, the spectrum and modulation signals looked the same on his test equipment. As long as the licensees are transmitting within the new specs, will they be in compliance?
 
Answer: No. To be compliant with the commission’s rules, the radio must be specifically certificated for narrowband use under Part 90.
 
Question 3: Will tightening the frequency stability to below 2.5 parts per million (PPM) make a system compliant?
 
Answer: No. To be compliant with the FCC’s rules, the radio must be specifically certificated for narrowband use under Part 90.
 
Additionally, below we’ve provided an excerpt from the FCC Knowledge Database (KDB) on the subject of permissive changes as it relates to Part 90 refarming. The KDB page is available at: http://fjallfoss.fcc.gov/oetcf/kdb/forms/FTSSearchResultPage.cfm?id=20292&switch=P
 
Question (from FCC KDB): How will new applications and permissive change applications be handled for wideband and narrowband equipment in the Part 90 re-farming bands?
 
Answer (from FCC KDB): In WT Docket 99-87, FCC 03-34, the commission adopted new frequency bands for transmitters under Part 90 of the FCC rules. Under the new rules, equipment in the Part 90 re-farming frequency bands 150 – 174 and 421 – 512 MHz will no longer be issued with a 25-kilohertz emission designator. The new rules prohibit Equipment authorization of devices with 25-kilohertz channel spacing after Dec. 31, 2004.
 
The current policy to address this timeline is:
 
New Grants: Applications for new equipment authorization received before Jan. 1, 2005, will be granted with a wideband (25-kilohertz) emission designator as long as the equipment also has a narrowband (12.5- and/or 6.25-kilohertz) emission designator. Applications for new equipment authorization received after Dec. 31, 2004, will not be granted with a wideband emission designator.
 
Permissive Changes: A class I permissive change may not be used to add a narrowband emission designator to a wideband device. Only the FCC or a TCB (within 30 days of grant) may modify the text on a grant, and for a class I permissive change, no filing is submitted. Applications for a class II permissive change received before Jan. 1, 2005, may be submitted for any modification that meets the definition of a permissive change. The wideband channel will be listed on the grant. A class II permissive change may be submitted to add a narrowband emission designator to a wideband grant if no hardware changes are made to the device. If hardware changes are made to the device, a new FCC ID will be required. When a class II permissive change is submitted to add a narrowband emission designator, only the permissive change grant will show the narrowband emission designator. The original grant will not be modified to show the new narrowband emission designator. Applications for class II permissive changes for wideband-only equipment will not be accepted after Jan. 1, 2005. Applications for class II permissive changes for multimode equipment received after Dec. 31, 2004, will not be granted with a wideband emission designator. A class II permissive change may be submitted to add a narrowband emission designator to a wideband grant if no hardware changes are made to the device. If hardware changes are made to the device, a new FCC ID will be required. If a device that was previously granted with wideband and narrowband emission designators is submitted for a permissive change with modifications unrelated to the emission designators, the permissive change will be granted without the wideband emission designator. Applications for devices with only narrowband emission designators will be processed as they currently are now.
 
Permissive Change Example: Equipment is approved for 25-/12.5-kilohertz operation prior to Jan. 1, 2005. After Jan. 1, 2005, a component unrelated to the power output or frequency determining circuitry becomes unavailable and must be replaced with a similar component. The change meets the 2.1043 definition of a permissive change and is tested to determine if a class I or class II permissive change is appropriate. If the test results show a class I change is acceptable, then the process is complete, and the new device may be marketed. If the test results show a class II permissive change is required, an application is then submitted to the FCC or a TCB. For applications received after Jan. 1, 2005, the permissive change grant will not be issued because the original was with both 25- and 12.5-kilohertz emissions, but only with the 12.5-kilohertz emission. When a permissive change is filed for 25-/12.5-kilohertz equipment, the FCC will not require the device to show compliance with the 6.25-kilohertz requirements that become effective Jan. 1, 2005, per 90.203(j)(5).
 
Software Change to Remove Emission: When a software change is made to a device to remove an approved operating mode/emission designator, no permissive change is required unless the device was approved as a software-defined radio (SDR). If the device was approved as an SDR, a class III permissive change must be filed with the commission. TCBs cannot approve SDRs yet. 
 
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