Most ATS facilities, military towers; an ELT or EPIRB transmitting on 121.5MHz may make this frequency impractical for communications.
243.0 MHz VHF
AM Voice/data
Generally limited to line of sight.
Military emergency frequency.
123.1 MHz VHF
AM Voice
Generally limited to line of sight.
SAR operations; on-scene comm.
2182 kHz HF
R3E, H3E, J3E, J2A, J2B
radiotelephony
Generally less than 300 miles for average aircraft installations.
International Maritime voice distress, safety, and calling frequency.
Silence period on this frequency are observed for three minutes (3 min.) twice an hour. Beginning on the hour and at 30 minutes past each hour to facilitate reception of distress calls.
Ships, boats at sea, Coast Guard Stations, commercial coast stations.
3023 kHz HF
4125 kHz HF
5680 kHz HF
R3E, H3E, J3E,
J2A, J2B
radiotelephony
Several thousand miles depending upon propagation conditions.
Alternate on-scene and SAR coordination communications.
Vessels and aircraft SAR coordination.
500 kHz MF
CW, telegraphy
Generally less than 100 miles for average aircraft installations.
Ships at sea, Coast Guard Stations, FSS, and commercial coast stations. Use is decreasing due to advanced comm. technology. As of February 1999, international requirements to have this capability aboard ships ceased.
156.8 MHz, VHF
Channel 16
FM, voice
Line of sight
International VHF maritime voice distress, safety and calling frequency.