Single Channel Air-Ground Radio System, commonly known as SINCGARS "sink-gars", FM or Fox Mike radio. SINCGARS and FM are used in conjunction with HF-SSB systems, UHF/SHF/EHF SATCOM and other communications systems for tactical military communications purposes.
VHF Tactical FM Land Mobile Air-Ground Military Communications
VHF-FM tactical radio system, with frequency-hopping and voice encryption/data encryption capabilities. Operating in the 30.000 to 87.975 MHz frequency band with 25 kHz channel steps. Uses 150.0 Hz CTCSS squelch system. Operates in single-channel (SC) and frequency-hopping (FH) modes for voice and data. Most radios include repeater capability (called RETRANS or retransmit in military usage). Compatible with previous-generation FM radios such as the PRC-25, PRC-77, PRC-1077, HH7700 and dozens of other similar tactical handheld, manpack and vehicle-mounted radios operating in the 30-76 MHz (30.00 to 75.95 MHz in the original PRC-25/PRC-77 and VRC-12 channeling) or 30-88 MHz range. NATO military forces and many other military forces use similar frequencies for tactical purposes, almost always with FM voice. The US military fields radios that operate in the 30-174 MHz and 30-512 MHz ranges to support SINCGARS, regular VHF-FM, 136-174 MHz VHF-high band services like VHF marine, aircraft radios, SATCOM and interoperability with other radio systems that use VHF/UHF.
In the United States, the military uses a combination of SINCGARS and VHF/UHF trunking systems for communications. The US government VHF-low bands are used in addition to the civilian bands on a non-interference basis. This includes use of the 50-54 MHz 6-meter amateur radio band and various portions of the VHF low band Business Radio frequency bands.
However, certain bands in the 30-50 MHz range (VHF low band) are allocated to exclusive government/military use. There are non-military government users of these frequencies, however most federal government agencies have moved to the 162-174 MHz and/or 406-420 MHz federal bands with the proliferation of trunking systems. There are still some wide-area networks such as the Tennessee Valley Authority's backup system that operates in the 40-42 MHz band.
Federal Government and Military Only Bands 30-50 MHz
This list applies to the United States only. The US military will often use frequencies outside these bands on a non-interference basis. In Europe, CEPT standardizes the 30.300 MHz - 30.500 MHz, 32.150 MHz - 32.450 MHz and 41.000 MHz - 47.000 MHz band as "harmonized" military bands for NATO and allied military tactical radio use.
|30.000 MHz to 30.550 MHz|
|32.000 MHz to 33.000 MHz|
|34.000 MHz to 35.000 MHz|
|36.000 MHz to 37.000 MHz|
|38.000 MHz to 39.000 MHz|
|40.000 MHz to 42.000 MHz|
|46.600 MHz to 47.000 MHz|
|49.600 MHz to 50.000 MHz|
It should be noted that military operations in single channel mode are found on any frequency between 30.000 and 87.975 MHz outside the government/military exclusive use bands on a non-interference basis. Use of the 150.0 Hz CTCSS or PL tone squelch allows for frequency sharing with other users, combined with the fact that civilian allocations in the 30-50 MHz band use 20 kHz channel steps, compared to the 25 kHz channeling used by military VHF-FM or SINCGARS systems.
It is important to note that in SC mode or single channel mode, SINCGARS radios allow for -5 kHz / +5 kHz or -10 kHz / +10 kHz offsets, effectively changing the 25 kHz frequency step to 5 kHz frequency step, allowing for use of non-standard frequencies in single-channel mode. In FH mode or frequency hopping mode channels are 25 kHz frequency steps. US government (and some older-generation military) land mobile systems use 10 kHz or 20 kHz channel steps in the above-listed bands as well. Use of standard land mobile CTCSS or PL tones have been reported (cf. the TVA's 40 MHz land mobile system uses 203.5 Hz PL and 250.3 Hz PL with 20 kHz channel spacing, even though the same band is used for military communications. The TVA channels naturally avoid use of 40.500 MHz - the military tactical band FM emergency channel.)
Background and History
SINCGARS evolved from basic simplex and duplex military systems operating in the low to mid VHF range (30.00 to 75.95 MHz) starting with the revolutionary PRC-25 radio. The PRC-25 (and associated VRC-12 vehicle radio set) utilized 150.0 Hz CTCSS squelch combined with indent channelization for frequency control vs. manual tuning with a VFO greatly simplified radio operation. The CTCSS system removed the need for adjustable squelch and made it easy for the average solider to use a radio with minimal training. The PRC-25 and PRC-77 (and dozens of clones, improvements, etc.) are considered hallmarks of battlefield communications simplicity and function. Their origin lies in WWII with the adoption of the SCR-300 (BC-1000) backpack (manpack) radio developed and manufactured by Motorola.
The US military pioneered the use of FM voice on the battlefield in World War II with the original "three band" system, allocating 20 to 27.9 MHz to armor (100 kHz steps), 27 to 38.9 MHz to artillary (100 kHz steps) and 38 to 54.9 MHz to infantry (100 kHz steps). The famous BC-1000 or SCR-300 backpack radio fielded in WWII operated in the 40 to 48 MHz range using 200 kHz steps and FM voice (falling within the 38-55 MHz "infantry band". Tank radios with FM provided vast improvement over AM-based systems on the battlefield. While the SCR-300 / BC-1000 did use a VFO, it featured channels labelled on the display instead of frequency and included a fine-tuning/adjustment signal generating function for battlefield fine tuning. Its use did require adjustment of the squelch and fine-tuning (meaning that the operator still needed to be trained in its use, compare to the PRC-25/PRC-77/VRC-12 family of radios, that are "soldier-proof"). With the adoption of the PRC-25/VRC-12 radios the "three band" system was abandoned, allowing cross-unit communications without the need for multiple radios. It also provided considerably more available channels (30-76 MHz in 50 kHz steps - 920 available channels vs. 20-55 MHz in 100 kHz steps - 350 available channels). Use of HF SSB and CW systems continued throughout the Vietnam war and up to the present day for long range communications and special operations uses.
The SCR-300 and similar high-HF/low-VHF radios developed in WWII and the Korean War revolutionized small unit tactics. First the capability for a platoon or similar level unit to communicate with its headquarters or commanding elements and then the capability for each man in a squad for fireteam to communicate with each other in addition to the longer-range communications capability for platoon-to-commander and platoon-to-platoon communications using FM radio have changed the battlespace forever. The basic military backpack radio (and now handheld radio) concept has been copied endlessly, to the point where even militias and guerrilla forces use similar VHF/UHF radios for similar purposes. For example, see Ukraine militia forces using Baofengs (UV-5R, UV-82 and similar VHF/UHF handheld Chinese radios) and fighters in Afghanistan using Icom IC-V8s and other 2 meter / VHF handheld radios for battlefield tactical purposes, often in conjunction with 26-28 MHz CB type equipment or other similar radios/bands.
Communist Bloc countries, including the Soviet Union (and former Soviet Union, now Russia), Poland, as well as Western and Central European military forces also use similar frequency ranges (for example, 26 MHz - 70 MHz is/was a popular frequency split for tactical radios, instead of 30-76 MHz). Various handheld and manpack radios covering these bands have been manufactured and used in various countries.
Captured radios from Iraq in the first and second Gulf Wars (Iraq Wars) indicate the 30-76 MHz (in 25 kHz steps, FM mode) band was used heavily by the Iraqi Army for tactical communications. The Iraqi military apparently used Italian made manpack and vehicle radios, as well as Soviet/Russian radios in the same frequency band. The PRC-638 manpack (backpack portable or transportable) radio made by IRET in Italy covers 30.000 MHz to 79.975 MHz in 25 kHz steps, with selector switches for 30 MHz/40 MHz/50 MHz/60 MHz/70 MHz, rotary decade switches for 0-9 and then a selector for 00 kHz, 25 kHz, 50 kHz or 75 kHz. For example, to select the frequency 31.575 MHz, the user would select "3", "1", "5" and then "75" on the radio's panel. This is very similar in operation to the PRC-25/PRC-77 and VRC-12 series of radios.
As discussed in previous paragraphs, there is a move to COTS equipment, including non-standard radios such as amateur radios, VHF marine band radios, CB/11 meter radios and other land mobile radios in the VHF/UHF band for tactical purposes. Unfortunately, VHF low and VHF mid band does not work well in heavily built up areas (i.e. urban warfare radios). High band VHF and UHF work considerably better in these environments. It is because of this that the modern PRC-148 and PRC-152 radios cover 30-512 MHz instead of just 30-76 MHz or 30-88 MHz.
Improvements with radio technology allowed for all three bands to be combined and moved from 20-55 MHz to 30-76 MHz and eventually 30-88 MHz, reducing channel spacing from 100 kHz to 50 kHz (Vietnam War) to 25 kHz (SINCGARS and present day). With the addition of frequency-hopping (ECCM - electronic counter-counter measures or anti-jam) and voice encryption (COMSEC) the FM radio became the standard battlefield tactical radio for ground and air communications. In the United States, most military systems still use 50 kHz step compatible frequencies for range control (cf. Fort Hood Range Control on 30.450 MHz is often heard during 11m/CB/10m and VHF low band band openings). See the frequency bands above. The 30 MHz, 32 MHz, 34 MHz, 36 MHz, 38 MHz, 40 MHz, 41 MHz and 46/47 MHz bands are very popular for CONUS-based military communications.
Evolution of military FM radio tactical radio bands: World War II, Korea and Beginning of Vietnam War (roughly 1940-1965)
|Frequency Band||Use||Channel Step/Frequency Spacing|
|20.000 MHz to 27.900 MHz||Armor Band (tank radio, tank destroyers, tank command nets)||100 kHz (channels 200-279), PRC-8, PRC-8A, SCR-508, SCR-509, SCR-510, SCR-528, SCR-538, etc|
|27.000 MHz to 38.900 MHz||Artillery Band||100 kHz (channels 270-389), PRC-9, PRC-9A, SCR-608, SCR-609, SCR-610, SCR-628|
|38.000 MHz to 54.900 MHz||Infantry Band||100 kHz (channels 380-549), PRC-10, PRC-10A, BC-1000/SCR-300 (partial, 40-48 MHz only)|
|40.000 MHz to 48.000 MHz||Infantry Band (partial)||200 kHz (channels 0-40), SCR-300 (BC-1000) manpack backpack radio|
Most of Vietnam War and Cold War (roughly 1965-1980s)
|Frequency Band||Use||Channel Step/Frequency Spacing|
|30.000 MHz to 75.950 MHz||Tactical Band (30-76 MHz) (150 Hz CTCSS "new squelch" system) removes need for manual squelch control||50 kHz (channelized intent frequency control) PRC-25, PRC-77, VRC-12 and dozens of others|
|Frequency Band||Use||Channel Step/Frequency Spacing|
|30.000 MHz to 87.975 MHz||Tactical Band (30-88 MHz) 150 Hz CTCSS (some radios allow use of other tones)||25 kHz step, single channel SC (fixed frequency) mode or frequency hopping FH (anti-jamming countermeasure) mode|
|30 MHz to 512 MHz||Tactical Band (30-88 MHz) combined with VHF/UHF bands, including the airband, VHF marine band, VHF land mobile bands||25 kHz step, single channel SC (fixed frequency) mode or frequency hopping FH (anti-jamming countermeasure) mode, 2.5, 5, 8.33 kHz steps|
|380-430 MHz||Intra-Squad Radio (ISR) and Improved Intra Squad Radio (IISR) systems||Various frequency steps and modes used for short range communications within squads/fireteams|
|2400-2500 MHz (2.4 GHz)||Intra-Squad Radio (ISR) and Improved Intra Squad Radio (IISR) systems||Various frequency steps and modes (including spread spectrum and frequency hopping) used for short range communications within squads/fireteams|
Amateur Radio Operators Using Surplus Military Equipment
Because previous-generation, vintage or antique military radios with 30-76 MHz or 30-88 MHz frequency bands cover the 6 meter amateur band, and WWII and Korean War vintage equipment covers 20-28 MHz or 20-27.9 MHz and 27-38.9 MHz or 27-39 MHz amateur radio operators will often use surplus equipment in the 10 meter and 6 meter bands for FM communications. Vintage military radio equipment is also used by amateur operators in the HF bands and VHF bands above 6 meters where available. This includes the 4 meter band around 70 MHz, which is available in select countries for amateur use. The PRC-8/PRC-8A (20 MHz-28 MHz), PRC-9/PRC-9A (27 MHz-39 MHz), PRC-10/PRC-10A (38 MHz-55 MHz), PRC-25, PRC-77 and similar radios are very popular with amateur or ham radio operators who keep these vintage radios alive by operating them on the amateur bands.
51.0 MHz is the most common military amateur radio frequency on 6 meters, as this allows for compatability with 100 kHz channel steps, 50 kHz channel steps, 25 kHz channel steps and tunable radios such as the PRC-10 or PRC-10A. Before the adoption of the PRC-25 and VRC-12 family of radios, armor (tanks), artillery and infantry each had their own radio bands (20-28 MHz for armor/tanks, 27-39 MHz for artillery and 38-55 MHz [or some subset thereof] for infantry). For example, the famous walkie-talkie backpack or manpack radio SCR-300 (BC-1000) covered 40-48 MHz in 100 kHz steps while the PRC-6 "banana radio" handheld transceiver or HT covered 47-55.4 MHz.
With the adoption of the PRC-25 and VRC-12 family of radios (and associated fixed and aircraft radios), armor, artillery and infantry could all communicate using the same radios, greatly improving tactical battlefield communications in time for the Vietnam War.
See Radio Nerds for a large library of resources on military radio gear, including technical and operations manuals.