In order for a TCB to review and approve a radio device, the device must be covered by the current applicable rules. Under some parts of the rules, definitions were ambiguous or the methodology used was based on an interpretation or a technical opinion, and was not officially documented in the rules. For certain parts of the rules, FCC also adopted new rule makings, which are now applicable. This article addresses the updated Part 15.C rules and examines the various changes and their effects.

Adoption of the changes was also based in part on recently adopted proposals for rule making concerning spread-spectrum devices. Other changes were implemented to clarify the Part 15 rules to help facilitate the TCB program. Although most of the rule changes affected primarily spread-spectrum radios, some proposed changes are effective across all unlicensed transmitter devices.

The FCC lab released three public notices specifically addressing test methods for frequency-hopping spread-spectrum devices, the definition of unique connectors, and the definition of modular approvals. These notices were intended to clarify ambiguous parts of the rules because TCBs are prohibited from certifying products not defined under the rules.

For example, FCC had accepted a generic definition of a module radio, allowing these spread-spectrum transmitters to be certified as module devices, despite having no official reference in the FCC rules. The unofficial rule interpretation helped industry solve a need, but without an official FCC public notice or rule making, a TCB was not sanctioned to qualify such a device as a radio module.

In another case, changes to the frequency-hopper rules were adopted based on a request for a rule change by the HomeRF group and other interested parties. These groups requested that FCC allow higher data rates than the existing 2 Mb/sec for frequency-hopping spread-spectrum devices.

FCC Part 15.203 states that intentional radiators operating under this rule shall be designed so that no antenna other than that furnished with it by the responsible party shall be used with the device. The reason for adopting this rule was to prevent the use of unapproved, aftermarket high-gain antennas or third-party amplifiers with a device or system.

To meet this requirement, FCC allows several options. The first option is a permanently attached antenna. These antennas usually include those devices for which the box must be opened to remove the antenna, a nonstandard tamperproof screw secures the antenna to the box, the antenna is soldered to the box, or the antenna is molded into the radio.

The second option is that the antenna be professionally installed. FCC's definition of professional installation had been somewhat ambiguous. For the most part, however, high-gain antennas designed to be mounted on a building exterior or a mast generally fall under the professional-installation clause. (The definition of professional installer does not include your brother-in-law simply because he can work the VCR remote or plug in the DVD player.) FCC's definition (though unofficial) is a properly trained person whose normal job function includes this type of work. The National Association of Radio and Telecommunications Engineers now has a certification program for unlicensed wireless systems installers in order to clarify the qualifications and definition of a professional installer for the industry.

The third option allows a nonstandard or unique connector to secure the antenna to the transmitter. An FCC public notice was released to clarify what qualifies as a unique connector. FCC clearly defines as standard such connectors as BNC, F, N, banana, and other readily available connectors. FCC unofficially defines this as a litmus test. Industry commonly refers to this list as the Radio Shack test: If the connector is available at Radio Shack, then it is not considered unique. FCC did allow for connectors such as the MCX and MMCX (which can be bought at some amateur radio stores) because these small connectors usually require someone with a professional skill set to work with those devices because of their size.

FCC Public Notice DA 00-1087 (released May 22, 2000) provided a new definition of unique connector for the industry.¹ Some connectors that had previously been ruled as nonstandard were redefined as standard. The public notice also gave a very short time period in which to comply with the new rules. This date has been changed twice due to industry filings, and the implementation date has now been indefinitely rolled back.

One major misunderstanding in industry was that the new definition meant that all devices after the implementation date required a new unique connector. Rather, it meant only that a design being approved after the implementation date required a new connector.

Under the new definition, FCC defines readily available as being for sale on the Internet or through catalogs. Whether the requirements of the public notice will be adopted is currently under review at FCC.

Modular Radio Approval. One of the stipulations of the TCB program is that TCBs cannot approve a device that is not covered by a specific rule. Based on that requirement, a TCB could not approve a spread-spectrum transmitter as a module device.

Although not specifically stated in the rules, since 1996 FCC has allowed transmitters that meet specific criteria to be certified as stand-alone radio modules. This enabled radio manufacturers to obtain approval for their devices as stand-alone products that could then be integrated into host devices without retesting the radio portion or obtaining an additional FCC certification. As long as approved antennas are used with the system, no recertification of the transmitter portion of the product is needed. However, the entire host device with the radio must be tested for emissions. This type of approval covers radios designed on printed circuit boards such as PCMCIA cards, bus cards, or any board for which the manufacturer can demonstrate a true module approval.

Under FCC Public Notice DA 00-1407 (released June 26, 2000), a radio can be approved as a module if it meets the following criteria:²

Wideband Frequency Hoppers. FCC released its first Report and Order ET Docket No. 99-231 on August 8, 2000.³ This was based on FCC Notice of Proposed Rule Making (NPRM) 99-149, which covered two distinct topics addressing spread-spectrum issues. The first topic covered in this report and order addressed the increase of allowable bandwidth for frequency-hopping (FH) devices. The increase in the FH bandwidth by a factor of 5 would allow FH systems to increase their data rates in order to be somewhat comparable to direct-sequence systems currently on the market.

Under existing FCC rules for spread-spectrum, FH devices were limited to a maximum 20-dB bandwidth of 1 MHz, which limited data rates to 2 Mb/sec. The HomeRF working group proposed to FCC that these devices be allowed to use 5-MHz-wide hopping channels to take advantage of higher data rates.

The adopted increase in bandwidth, however, came at a cost. For those FH systems operating with 1-MHz bandwidth, the transmitter-conducted power is 1 W peak output, plus 6 dBi gain allowed for the antenna, which provides a total of 4 W effective isotropic radiated power (EIRP). For systems operating at the 5-MHz bandwidth, the power has been reduced to 125 mW transmitter-conducted peak power output, plus 6 dBi gain for the antenna. That is about 3/4 W EIRP of total power with the antenna.

FCC did reduce the number of hopping channels from a minimum of 75 to a minimum of 15 channels for the 5-MHz- wide bandwidth in a 75-MHz system. To obtain the 20-dB bandwidth for 5 MHz and the total number of hops per the 20-dB bandwidth, one must measure from the 20-dB point on the low side of the lowest signal to the 20-dB point on the high side of the highest frequency selected. The hopping time for the 15 channels is 2.5 seconds per channel, versus the 400 milliseconds maximum for the 75 hopping channels (see Table I).

Frequency-Hopping Spread-Spectrum Test Methodology

FCC released Public Notice DA 00-705 on March 30, 2000.⁴ This public notice covered test methodology for frequency-hopping spread-spectrum devices. The public notice was based on input from the TCB work committee assigned to support this task. This notice included the requirements for the test software and the required radio modes for properly testing an FH product. The test methodology includes SAR and MPE requirements, power output measurements, and bandwidth measurements. Although written for 1-MHz-wide systems, the methodology can be easily adopted for use with 5-MHz-wide systems.

Unintentional Radiator. FCC has recently made one major change to the requirements that does affect transmitters. FCC will no longer accept certification for any type of digital device. The digital portion of the transmitter must now be approved under the declaration of conformity route.

Over the last year, FCC has made some significant changes to the Part 15 rules and more changes are under consideration. Among those being considered is a change to the Part 15 rules to allow the use of a new technology called ultrawide band. This low-power radio system would operate under Part 15.209 limits and use up to a 2–3-GHz frequency band.

FCC is also researching test methodologies for millimeter devices and for short-range, high-speed wireless digital communication devices that use the unlicensed national information structure (U-NII) band. Other items under consideration include allowing the use of wideband orthogonal frequency division multiplexing (W-OFDM) in the 2.4 GHz band and allowing direct sequence processing gain measurements under the second part of NPRM 99-149. FCC is planning to hold an open forum session on the Part 15 rules sometime in early 2001.