Radio silence
In
The term "radio station" may include anything capable of transmitting a radio
Amateur radio Wilderness Protocol
The Wilderness Protocol recommends that those stations able to do so should monitor the primary (and secondary, if possible) frequency every three hours starting at 7 AM, local time, for 5 minutes starting at the top of every hour, or even continuously.
The Wilderness Protocol is now included in both the ARRL ARES Field Resources Manual[2] and the ARES Emergency Resources Manual. Per the manual, the protocol is:
The Wilderness protocol (see page 101, August 1995 QST) calls for hams in the wilderness to announce their presence on, and to monitor, the national calling frequencies for five minutes beginning at the top of the hour, every three hours from 7 AM to 7 PM while in the back country. A ham in a remote location may be able to relay emergency information through another wilderness ham who has better access to a repeater. National calling frequencies: 52.525, 146.52, 223.50, 446.00, 1294.50 MHz.
Priority transmissions should begin with the LITZ (Long Interval Tone Zero or Long Time Zero) DTMF signal for at least 5 seconds. CQ like calls (to see who is out there) should not take place until after 4 minutes after the hour.
Maritime mobile service
Distress calls
Radio silence can be used in nautical and aeronautical communications to allow faint distress calls to be heard (see
Silent periods
Up until the procedure was replaced by the Global Maritime Distress and Safety System (August 1, 2013 in the U.S.), maritime radio stations were required to observe radio silence on 500 kHz (radiotelegraph) for the three minutes between 15 and 18 minutes past the top of each hour, and for the three minutes between 45 and 48 minutes past the top of the hour; and were also required to observe radio silence on 2182 kHz (upper-sideband radiotelephony) for the first three minutes of each hour (H+00 to H+03) and for the three minutes following the bottom of the hour (H+30 to H+33).
For 2182 kHz, this is still a legal requirement, according to 47 CFR 80.304 - Watch requirement during silence periods.[4]
Military
An order for Radio silence is generally issued by the
In the British Army, the imposition and lifting of radio silence will be given in orders or ordered by control using 'Battle Code' (BATCO). Control is the only authority to impose or lift radio silence either fully or selectively. The lifting of radio silence can only be ordered on the authority of the HQ that imposed it in the first place. During periods of radio silence a station may, with justifiable cause, transmit a message. This is known as Breaking Radio Silence. The necessary replies are permitted but radio silence is automatically re-imposed afterwards. The breaking station transmits its message using BATCO to break radio silence.
The command for imposing radio silence is:
Hello all stations, this is 0. Impose radio silence. Over.
Other countermeasures are also applied to protect secrets against enemy signals intelligence.
Electronic emissions can be used to plot a line of bearing to an intercepted signal, and if more than one receiver detects it,
Other uses
Radio silence can be maintained for other purposes, such as for highly sensitive
In the USA, CONELRAD and EBS (which are now discontinued), and EAS (which is currently active) are also ways of maintaining radio silence, mainly in broadcasting, in the event of an attack.
Examples of radio silence orders
- Radio silencing helped hide the Japanese attack on Pearl Harbor in World War II.[9] The attackers had used AM radio station KGU in Honolulu as a homing signal.
- On June 2, 1942, during World War II, a nine-minute air-raid alert, including at 9:22 pm a radio silence order applied to all
- In January 1965, Syrian Armed Forces observed a period of radio silence which successfully detected Mossad spy Eli Cohen who was transmitting espionage work to Israel.
See also
References
- ^ Iraqi ships maintaining radio silence The Guardian
- ^ "ARES Field Resources Manual" (PDF).
- ^ U.S. Coast Guard, Radiotelephone Handbook, COMDTINST M2300.7
- ^ "47 CFR 80.304 - Watch requirement during silence periods".
- ^ Emissions Control 3 Mission Airforce Technology
- ^ George Musser (July 14, 2015). "New Horizons Emerges Unscathed from Pluto Flyby". Scientific American.
- ^ Jim Algar (November 15, 2014). "Philae Lander Historic Comet Mission Cut Short? Probe Goes on Radio Silence as Battery Depletes". Tech Times.
- ^ Charles Q. Choi (June 16, 2015). "New Spaceship Antenna Prevents Radio Silence During Fiery Re-Entry". Space.com.
- ^ Pearl Harbor National Geographic
- ^ "1942 World War II Chronology". www.sfmuseum.org. Retrieved 2019-04-07.