--- kind: "section" citation: "47 C.F.R. § 80.213" title: "47" number: "80.213" heading: "Modulation requirements." url: "https://uscodex.org/cfr/47/80.213" --- # §80.213. Modulation requirements. - (a) Transmitters must meet the following modulation requirements: - (1) When double sideband emission is used the peak modulation must be maintained between 75 and 100 percent; - (2) When phase or frequency modulation is used in the 156-162 MHz band the peak modulation must be maintained between 75 and 100 percent. A frequency deviation of ±5 kHz is defined as 100 percent peak modulation; and - (3) In single sideband operation the upper sideband must be transmitted. Single sideband transmitters must automatically limit the peak envelope power to their authorized operating power and meet the requirements in [§ 80.207(c)](/cfr/47/80.207.md?p=c). - (b) Radiotelephone transmitters using A3E, F3E and G3E emission must have a modulation limiter to prevent any modulation over 100 percent. This requirement does not apply to survival craft transmitters, to transmitters that do not require a license or to transmitters whose output power does not exceed 3 watts. - (c) Coast station transmitters operated in the 72.0-73.0 MHz and 75.4-76.0 MHz bands must be equipped with an audio low-pass filter. The filter must be installed between the modulation limiter and the modulated radio frequency stage. At frequencies between 3 kHz and 15 kHz it must have an attenuation greater than at 1 kHz by at least 40log10 (f/3) dB where “f” is the frequency in kilohertz. At frequencies above 15 kHz the attenuation must be at least 28 dB greater than at 1 kHz. - (d) Ship and coast station transmitters operating in the 156-162 MHz and 216-220 bands must be capable of proper operation with a frequency deviation that does not exceed ±5 kHz when using any emission authorized by [§ 80.207](/cfr/47/80.207.md). - (e) Coast station transmitters operated in the 156-162 MHz band must be equipped with an audio low-pass filter. The filter must be installed between the modulation limiter and the modulated radio frequency stage. At frequencies between 3 kHz and 20 kHz it must have an attenuation greater than at 1 kHz by at least 60log10(f/3) dB where “f” is the audio frequency in kilohertz. At frequencies above 20 kHz the attenuation must be at least 50 dB greater than at 1 kHz. - (f) Radiodetermination ship stations operating on 154.585 MHz, 159.480 MHz, 160.725 MHz, 160.785 MHz, 454.000 MHz and 459.000 MHz must employ a duty cycle with a maximum transmission period of 60 seconds followed by a minimum quiescent period four times the duration of the transmission period. - (g) Radar stations operating in the bands above 2.4 GHz may use any type of modulation consistent with the bandwidth requirements in [§ 80.209(b)](/cfr/47/80.209.md?p=b). - (h) Radar transponder coast stations using the 2900-3100 MHz or 9300-9500 MHz band must operate in a variable frequency mode and respond on their operating frequencies with a maximum error equivalent to 100 meters. Additionally, their response must be encoded with a Morse character starting with a dash. The duration of a Morse dot is defined as equal to the width of a space and 1/3 of the width of a Morse dash. The duration of the response code must not exceed 50 microseconds. The sensitivity of the stations must be adjustable so that received signals below −10 dBm at the antenna will not activate the transponder. Antenna polarization must be horizontal when operating in the 9300-9500 MHz band and either horizontal or both horizontal and vertical when operating in the 2900-3100 MHz band. Racons using frequency agile transmitting techniques must include circuitry designed to reduce interference caused by triggering from radar antenna sidelobes. - (i) Variable frequency ship station transponders operating in the 2900-3100 MHz or 9300-9500 MHz band that are not used for search and rescue purposes must meet the following requirements: - (1) Non-selectable transponders must have the following characteristics: - (i) They must respond on all their frequencies with a maximum range error equivalent to 100 meters; - (ii) They must use a Morse encoding of “PS” (dot-dash-dash-dot, dot-dot-dot), meaning “You should not come any closer”. The width of a Morse dot is defined as equal to the width of a space and 1/3 of the width of a Morse dash; - (iii) When they employ swept frequency techniques they must not transmit on any frequency for more than 10 seconds in any 120 second period; - (iv) Any range offset of their response must occur during their pause on the fixed frequency; - (v) The duration of the response code must not exceed 50 microseconds; - (vi) The sensitivity of the stations must be adjustable so that received signals below −10 dBm at the antenna input will not activate the transponder; - (vii) Antenna polarization must be horizontal when operating in the 9300-9500 MHz band and either horizontal or both horizontal and vertical when operating in the 2900-3100 MHz band. - (viii) Transponders using frequency agile techniques must include circuitry designed to reduce interference caused by triggering from radar antenna sidelobes. - (2) Selectable transponders must be authorized under [part 5](/cfr/47/part5.md) of the Commission's rules until standards for their use are developed. - (j) The transmitted signals of search and rescue transponders must cause to appear on a radar display a series of at least 20 equally spaced dots. - (k) **The modulation requirements for EPIRB's are contained in subpart V.** ## Notes ### Amendments [51 FR 31213, Sept. 2, 1986, as amended at 52 FR 7418, Mar. 11, 1987; 52 FR 28825, Aug. 4, 1987; 54 FR 40058, Sept. 29, 1989; 57 FR 43407, Sept. 21, 1992; 65 FR 77824, Dec. 13, 2000; 68 FR 46965, Aug. 7, 2003; 69 FR 64673, Nov. 8, 2004] ### Authority Authority: 47 U.S.C. 151-155, 301-609; 3 U.S.T. 3450, 3 U.S.T. 4726, 12 U.S.T. 2377. ### Source Source: 51 FR 31213, Sept. 2, 1986, unless otherwise noted. ### Amendments [51 FR 31213, Sept. 2, 1986, as amended at 52 FR 7418, Mar. 11, 1987; 52 FR 28825, Aug. 4, 1987; 54 FR 40058, Sept. 29, 1989; 57 FR 43407, Sept. 21, 1992; 65 FR 77824, Dec. 13, 2000; 68 FR 46965, Aug. 7, 2003; 69 FR 64673, Nov. 8, 2004]