The frequency listed or displayed for a radio station can differ, depending upon the radio receiver, the type of modulation used and how you are demodulating (or modulating) the signal, and the person listing the frequency. This is especially true for high frequency (HF) radios. To help avoid confusion, three terms are used to describe these radio frequencies: assigned, carrier, and window.
The assigned frequency is defined by the International Telecommunications Union Radio Regulations as "the centre of a frequency band assigned to a station". In fact, it is the actual radio frequency of the signal being transmitted and received. This is the most commonly used frequency designation.
The carrier frequency is the frequency of the carrier, or the suppressed carrier of a signal. For many, perhaps most radio signals, the carrier frequency and the assigned frequency are identical. They are identical for AM (dual sideband) signals. They are different for single sideband radios. For maritime HF single sideband transmissions, which are always upper sideband, the assigned frequency is always 1.4 kHz greater than the carrier frequency.
The carrier frequency designation, not the assigned frequency designation, is normally used in referring to single sideband transmissions. History partially explains the reason for this. Marine radiotelephony was originally AM (dual sideband), and the carrier and assigned frequencies were the same. Certain frequencies, such as the distress and calling frequency 2182 kHz, were internationally recognized and known by any mariner using a marine radiotelephone. When marine spectrum became scarce, the International Telecommunications Union moved all marine radiotelephony transmissions from dual sideband to the more efficient single sideband. At first, the carrier signal was left untouched, so old AM radios could still receive the new single sideband transmissions. In time however, the old carrier signal was eliminated. The old marine frequencies such as 2182 kHz, commonly known and used, were retained and still displayed by marine radios. Although no signal was actually transmitted on these carrier frequencies any longer, receivers still had to be tuned to those frequencies so that the voice signal could be properly demodulated and understood.
Maritime digital signals, such as narrow band direct printing (NBDP or sitor) or digital selective calling (DSC), are transmitted on an assigned frequency 1.7 kHz above the (suppressed) carrier frequency. Marine weatherfax signals are transmitted on an assigned frequency 1.9 kHz above the carrier frequency. NBDP, DSC and weatherfax radios normally display the assigned frequency. However, if a single sideband radio with a separate decoder unit is used to receive a sitor, DSC or weatherfax signal, it's likely that receiver would have to be tuned to the carrier frequency for the decoder to work properly.
The ITU assigned channel numbers to many single sideband and NBDP frequencies to help avoid this confusion. However, DSC frequencies, and most simplex single sideband, NBDP and weatherfax frequencies do not have channel numbers.
The window frequency is simply the frequency displayed (on the front panel numeric display "window") by a particular radio receiver or transmitter. Depending on the equipment, the window frequency could be either the carrier or the assigned frequency. Since the window frequency is dependent upon the equipment used, the term is not generally used by the USCG.
The USCG tries to use standard convention in its listing of radio frequencies: Single sideband frequencies are generally carrier frequencies; all others are generally assigned frequencies. When the carrier and assigned frequencies differ, we generally list both.
Read your radio's instruction manual, or talk to your marine electronics dealer, to learn whether your radio should be tuned to the assigned or the carrier frequency.
Carrier Frequency (kHz) |
Geographic Area |
|
2003.0 |
Great Lakes only |
|
2782.0 |
Mississippi River System working frequency |
|
2082.5 |
All Areas. Also, Intership non-commercial fishing. |
|
2086.0 |
Mississippi River System working frequency |
|
2093.0 |
All Areas. |
|
2142.0 |
Pacific Coast, daily, south of 42 deg. N |
|
2182.0 |
Distress, safety and calling |
|
2203.0 |
Gulf of Mexico. Also, Intership non-commercial fishing. |
|
2214.0 |
All Areas. |
|
2635.0 |
ITU Regions 2-3 (ITU RR 4193). Not in FCC rules. |
|
2638.0 |
All Areas. |
|
2670.0 |
U.S. Coast Guard Liaison and Maritime Safety Broadcasts, Also Intership Safety and Operational Communications in all areas. |
|
2738.0 |
All Areas, except Great Lakes. Shared with aircraft. |
|
2830.0 |
Gulf of Mexico only. Shared with aircraft. |
Carrier Frequency (kHz) |
Geographic Area |
|
2065.0 |
All Areas. |
|
2079.0 |
All Areas. |
|
2096.5 |
All Areas. |
|
3023.0 |
Government shore, ship and aircraft stations for search and rescue coordination. |
Reference: FCC Regulations, 47 CFR 80.373(b) and (c), except as noted. Assignments are required before these frequencies can be used by land stations. Duplex channels are not available in this band.
Commandant (G-SCT-2)
U.S. Coast Guard 27 Aug 1999
Washington DC 20593
HF Single Sideband Maritime Radiotelephone Channels
4 MHz Duplex Channels
ITU Channel No. Coast Transmit Ship Transmit
401 4357 kHz 4065 kHz
402 4360 4068
403 4363 4071
404 4366 4074
405 4369 4077
406 4372 4080
407 4375 4083
408 4378 4086
409 4381 4089
410 4384 4092
411 4387 4095
412 4390 4098
413 4393 4101
414 4396 4104
415 4399 4107
416 4402 4110
417 4405 4113
418 4408 4116
419 4411 4119
420 4414 4122
421 4417 4125 (Calling; distress
& safety working on
4125 kHz simplex)
422 4420 4128
423 4423 4131
424 4426 4134 (USCG Calling)
425 4429 4137
426 4432 4140
427 4435 4143
428 4351 (varies)
429 4354 (varies)
6 MHz Duplex Channels
ITU Channel No. Coast Transmit Ship Transmit
601 6501 (kHz) 6200 (kHz)(USCG Calling)
602 6504 6203
603 6507 6206
604 6510 6209
605 6513 6212
606 6516 6215 (Calling; distress
& safety working on
6215 kHz simplex)
607 6519 6218
608 6522 6221
8 MHz Duplex Channels
ITU Channel No. Coast Transmit Ship Transmit
801 8719 (kHz) 8195 (kHz)
802 8722 8198
803 8725 8201
804 8728 8204
805 8731 8207
806 8734 8210
807 8737 8213
808 8740 8216
809 8743 8219
810 8746 8222
811 8749 8225
812 8752 8228
813 8755 8231
814 8758 8234
815 8761 8237
816 8764 8240 (USCG Calling)
817 8767 8243
818 8770 8246
819 8773 8249
820 8776 8252
821 8779 8255 (Calling)
822 8782 8258
823 8785 8261
824 8788 8264
825 8791 8267
826 8794 8270
827 8797 8273
828 8800 8276
829 8803 8279
830 8806 8282
831 8809 8285
832 8812 8288
833 8291 8291
834 8707 (varies)
835 8710 (varies)
836 8713 (varies)
837 8716 (varies)12 MHz Duplex Channels
ITU Channel No. Coast Transmit Ship Transmit
1201 13,077 kHz 12,230 kHz
1202 13,080 12,233
1203 13,083 12,236
1204 13,086 12,239
1205 13,089 12,242 (USCG Calling)
1206 13,092 12,245
1207 13,095 12,248
1208 13,098 12,251
1209 13,101 12,254
1210 13,104 12,257
1211 13,107 12,260
1212 13,110 12,263
1213 13,113 12,266
1214 13,116 12,269
1215 13,119 12,272
1216 13,122 12,275
1217 13,125 12,278
1218 13,128 12,281
1219 13,131 12,284
1220 13,134 12,287
1221 13,137 12,290 (Calling)
1222 13,140 12,293
1223 13,143 12,296
1224 13,146 12,299
1225 13,149 12,302
1226 13,152 12,305
1227 13,155 12,308
1228 13,158 12,311
1229 13,161 12,314
1230 13,164 12,317
1231 13,167 12,320
1232 13,170 12,323
1233 13,173 12,326
1234 13,176 12,329
1235 13,179 12,332
1236 13,182 12,335
1237 13,185 12,338
1238 13,188 12,341
1239 13,191 12,344
1240 13,194 12,347
1241 13,197 12,35016 MHz Duplex Channels
ITU Channel No. Coast Transmit Ship Transmit
1601 17,242 kHz 16,360 kHz
1602 17,245 16,363
1603 17,248 16,366
1604 17,251 16,369
1605 17,254 16,372
1606 17,257 16,375
1607 17,260 16,378
1608 17,263 16,381
1609 17,266 16,384
1610 17,269 16,387
1611 17,272 16,390
1612 17,275 16,393
1613 17,278 16,396
1614 17,281 16,399
1615 17,284 16,402
1616 17,287 16,405
1617 17,290 16,408
1618 17,293 16,411
1619 17,296 16,414
1620 17,299 16,417
1621 17,302 16,420 (Calling)
1622 17,305 16,423
1623 17,308 16,426
1624 17,311 16,429
1625 17,314 16,432 (USCG Calling)
1626 17,317 16,435
1627 17,320 16,438
1628 17,323 16,441
1629 17,326 16,444
1630 17,329 16,447
1631 17,332 16,450
1632 17,335 16,453
1633 17,338 16,456
1634 17,341 16,459
1635 17,344 16,462
1636 17,347 16,465
1637 17,350 16,468
1638 17,353 16,471
1639 17,356 16,474
1640 17,359 16,477
1641 17,362 16,480
1642 17,365 16,483
1643 17,368 16,486
1644 17,371 16,489
1645 17,374 16,492
1646 17,377 16,495
1647 17,380 16,498
1648 17,383 16,501
1649 17,386 16,504
1650 17,389 16,507
1651 17,392 16,510
1652 17,395 16,513
1653 17,398 16,516
1654 17,401 16,519
1655 17,404 16,522
1656 17,407 16,52518/19 MHz Duplex Channels
ITU Channel No. Coast Transmit Ship Transmit
1801 19,755 kHz 18,780 kHz
1802 19,758 18,783
1803 19,761 18,786
1804 19,764 18,789
1805 19,767 18,792
1806 19,770 18,795 (Calling)
1807 19,773 18,798
1808 19,776 18,801
1809 19,779 18,804
1810 19,782 18,807
1811 19,785 18,810
1812 19,788 18,813
1813 19,791 18,816
1814 19,794 18,819
1815 19,797 18,822
22 MHz Duplex Channels
ITU Channel No. Coast Transmit Ship Transmit
2201 22,696 kHz 22,000 kHz
2202 22,699 22,003
2203 22,702 22,006
2204 22,705 22,009
2205 22,708 22,012
2206 22,711 22,015
2207 22,714 22,018
2208 22,717 22,021
2209 22,720 22,024
2210 22,723 22,027
2211 22,726 22,030
2212 22,729 22,033
2213 22,732 22,036
2214 22,735 22,039
2215 22,738 22,042
2216 22,741 22,045
2217 22,744 22,048
2218 22,747 22,051
2219 22,750 22,054
2220 22,753 22,057
2221 22,756 22,060 (Calling)
2222 22,759 22,063
2223 22,762 22,066
2224 22,765 22,069
2225 22,768 22,072
2226 22,771 22,075
2227 22,774 22,078
2228 22,777 22,081
2229 22,780 22,084
2230 22,783 22,087
2231 22,786 22,090
2232 22,789 22,093
2233 22,792 22,096
2234 22,795 22,099
2235 22,798 22,102
2236 22,801 22,105
2237 22,804 22,108
2238 22,807 22,111
2239 22,810 22,114
2240 22,813 22,117
2241 22,816 22,120
2242 22,819 22,123
2243 22,822 22,126
2244 22,825 22,129
2245 22,828 22,132
2246 22,831 22,135
2247 22,834 22,138
2248 22,837 22,141
2249 22,840 22,144
2250 22,843 22,147
2251 22,846 22,150
2252 22,849 22,153
2253 22,852 22,156 25/26 MHz Duplex Channels
ITU Channel No. Coast Transmit Ship Transmit
2501 26,145 kHz 25,070 kHz
2502 26,148 25,073
2503 26,151 25,076
2504 26,154 25,079
2505 26,157 25,082
2506 26,160 25,085
2507 26,163 25,088
2508 26,166 25,091
2509 26,169 25,094
2510 26,172 25,097 (Calling) HF Single Sideband Maritime Radiotelephone Channels
Simplex Channels
These frequencies are shared and are not available for the
exclusive use of any station.
4 MHz Band 6 MHz Band 8 MHz Band 12 MHz Band
4146 kHz 6224 kHz 8294 kHz 12,353 kHz
4149 6227 8297 12,356
6230 12,359
12,362
12,365
16 MHz 18/19 MHz Band 22 MHz Band 25/26 MHz Band
16,528 kHz 18,825 kHz 22,159 kHz 25,100 kHz
16,531 18,828 22,162 25,103
16,534 18,831 22,165 25,106
16,537 18,834 22,168 25,109
16,540 18,837 22,171 25,112
16,543 18,840 22,174 25,115
16,546 18,843 22,177 25,118
Maritime Channels Shared with the Fixed Service
The following channels in the band 4000-4063 kHz and 8100-8195 kHz may be used:
- for supplementing ship-to-shore channels for duplex operation;
- for intership simplex (single-frequency) and cross-band operation;
- for cross-band working with coast stations;
- for duplex operation with coast stations working in the band 4438-4650 kHz or
with Channels 834, 835, 836 and 837;
- for ship-to-shore or shore-to-ship simplex operations (8100-8195 kHz only).
4 MHz Carrier 8 MHz Carrier
Channel No. Frequency kHz Frequency kHz
1 4000 8101
2 4003 8104
3 4006 8107
4 4009 8110
5 4012 8113
6 4015 8116
7 4018 8119
8 4021 8122
9 4024 8125
10 4027 8128
11 4030 8131
12 4033 8134
13 4036 8137
14 4039 8140
15 4042 8143
16 4045 8146
17 4048 8149
18 4051 8152
19 4054 8155
20 4057 8158
21 4060 8161
22 -- 8164
23 -- 8167
24 -- 8170
25 -- 8173
26 -- 8176
27 -- 8179
28 -- 8182
29 -- 8185
30 -- 8188
31 -- 8191
Global Maritime Distress & Safety System Radiotelephone Channels
These simplex frequencies are used for distress and safety
communications, and (except for 2182 kHz) are not normally
guarded.
2182 kHz 8291 kHz
4125 12,290
6215 16,420