Sec. 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 
and 216-220 MHz bands the peak modulation must be maintained between 75 
and 100 percent. A frequency deviation of &177;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 Sec. 80.207(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 MHz bands must be capable of proper operation with a 
frequency deviation of #5 kHz when using any emission 
authorized by Sec. 80.207.
    (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 
Sec. 80.209(b).
    (h) Radar transponder coast stations using the 2920-3100 MHz or 
9320-9500 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 9320-9500 MHz band 
and either horizontal or both horizontal and vertical when operating in 
the 2920-3100 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 
2920-3100 MHz or 9320-9500 MHz band that are not used for search and 
rescue purposes must meet the following requirements:

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    (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 
9320-9500 MHz band and either horizontal or both horizontal and vertical 
when operating in the 2920-3100 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 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.
[ 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]