FCC Rules

Purpose

FCC rules and regulations are often misunderstood and misquoted. To aid in clarifying a lot of the misconceptions surrounding them in regards to wireless networking, we have tried to centralize a discussion about them here.

Disclaimer

None of us are lawyers. Everything expressed here is based on a regular person's interpretation of the rules, regulations and laws surround these issues. Before doing anything, SVWUX, its members and officers highly suggest that you retain counsel.

SVWUX, its members and officers may not be held liable for your actions resulting from anything printed here.

Definitions

Part 15

Part 15 refers to equipment and operation of equipment defined under Chapter 47 of the Code of Federal Regulations (CFR), Part 15. It defines the criteria for unlicensed usage of the radio spectrum. Most consumer-grade wireless networking (such as the IEEE 802.11 standards) fall into this category.

The FCC's website has the latest copy of Part 15.

Part 97

Part 97 refers to equipment and operation of equipment defined under Chapter 47 of the Code of Federal Regulations (CFR), Part 97. It defines the criteria for licensed usage of bands dedicated to amateur radio operators, or hams. Only licensed operators or individuals under the supervision of a licensed operator are allowed to transmit signals in these portions of the radio spectrum.

There are several sites dedicated to amateur radio, including:

The FCC's website has the latest copy of Part 97.

Maximum transmit power of Part 15 equipment

§ 15.247, titled "Operation within the bands 902-928 MHz, 2400-2483.5 MHz, and 5725-5850 MHz," governs the criteria for power output of Part 15 equipment that is both frequency hopping and digitally modulated. This criteria applies to most wireless networking standards.

According to § 15.247(b)(3), systems that employ digital modulation in the bands mentioned above are allowed to transmit at up to 1 Watt (30 dB) of power.

There are some exceptions to this rule, largely for directional antennae only:

2400 - 2483.5 MHz (2.4 GHz)

  • If an antenna with a directional gain greater than 6 dBi is used, the maximum power output shall be reduced by the amount (in dB) that the directional gain of the antenna exceeds 6 dBi. For example, if you want to use a 2.4 GHz directional antenna with a gain of 12 dBi, you cannot exceed a transmit power output of 30 dB - (12 dBi - 6 dBi) = 24 dB.
  • 15.247(c)(1)(i) "Systems operating in the 2400-2483.5 MHz band that are used exclusively for fixed, point-to-point operations may employ transmitting antennas with directional gain greater than 6 dBi provided the maximum conducted output power of the intentional radiator is reduced by 1 dB for every 3 dB that the directional gain of the antenna exceeds 6 dBi." For example, if you want to use a 2.4 GHz directional antenna with a gain of 12 dBi for fixed point-to-point operation only, you cannot exceed a transmit power output of 30 dB - [(24 dBi - 6 dBi) / 3 dB] = 24 dB.

5725 - 5850 MHz (5.8 GHz)

  • Part 15.247(c)(1)(ii) "Systems operating in the 5725-5850 MHz band that are used exclusively for fixed, point-to-point operations may employ transmitting antennas with directional gain greater than 6 dBi without any corresponding reduction in transmitter conducted output power."

This would seem like 802.11a, which operates in the 5.8 GHz range, is an ideal candidate for long range point-to-point operation, since it can be used at a full 1 Watt regardless of the antenna used.

Part 15 equipment reclassified under Part 97

Amateur radio operators love to "reclassify" unlicensed, low-power equipment under their licensed rules. They claim to be allowed to ignore the 1 Watt transmitter and antenna gain restrictions placed on Part 15 equipment/operation, and think they can use any antenna at up to 1500 Watts (the maximum allowed under Part 97). They're partially right and partially wrong.

Transmit power

Part 15 sets a hard limit on transmitter power within the 2400-2483.5 MHz and 5725-5850 MHz bands: 1 Watt. Amateur radio operators are not allowed to exceed this, except in certain cases:

  • To aid in the mitigation of an emergency
  • Overlap on licensed bands

In the 2400-2483.5 MHz band, amateur radio has been licensed a small chunk for use with amateur television (2390-2450 MHz). This roughly corresponds to channels 1 thru 5 of the 802.11 specification. On these channels, amateur radio operators can exceed the 1 Watt of transmitter power by using external amplifiers connected between their equipment and antenna. However, on all other channels in that range, they must abide by the 1 Watt restriction defined under Part 15.

The one place where amateur radio operators really win big is antenna gain. There is no gain limit on the antenna used by an amateur radio operator -- that is, there is no power reduction if the antenna gain exceeds the limits defined in Part 15.

Priority over Part 15 Users

Since amateur radio's purpose is to relay emergency communications, operators normally enjoy a privileged status in the radio spectrum. However, this priority usage is limited to two scenarios:

  1. Bands licensed to amateur radio
  2. Emergency traffic in or out of the normal amateur radio bands

The most common time when this becomes an issue is in the 2.4 GHz band (2400-2483.5 MHz). Amateur radio has been licensed a small chunk for use with amateur television (2390-2450 MHz). This roughly corresponds to channels 1 thru 5 of the 802.11 specification. On these channels, amateur radio operators can declare priority usage over Part 15 operators. However, on all other channels (including the 5.8 GHz band), amateur radio operators have no priority.

Miscellaneous Rules

For an amateur radio operator to reclassify Part 15 equipment under their Part 97 license, they must abide by the rules defined in Part 97, including, but not limited to:

  1. Every 10 minutes, the operator's call sign must be transmitted in clear text (§ 97.119(a)). This is usually done by including the call sign in the SSID of the wireless network.
  2. All traffic must be unencrypted.*

* According to § 97.113(a)(4), amateur operators must not sent "messages encoded for the purpose of obscurring their meaning." This is generally accepted as a unilateral declaration that all traffic must be unencrypted. However, it can be debated that the purpose of some encryption is to maintain data privacy -- especially in the case where an amateur operator is passing along medical information. We will continue to research this area; for now, please read Part 97 and all corresponding FCC regulations and determine this answer for yourself.

Additional Resources

ARRL

Federal Communications Commission

RadioExam.org

Topic revision: r5 - 2009-11-13 - 02:22:13 - AndrewBrown
 
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