From HFUnderground

Jump to: navigation, search

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 military communications purposes.


VHF Tactical FM Land Mobile Air-Ground Military Communications

Two Harris RT-1523 SINCGARS ASIP radios with ECCM capability for anti-jam and secure voice and data for tactical military communications, shown in use by the US military
Two handheld VHF-FM tactical radios Datron HH7700 30-88 MHz (30.000 MHz to 87.975 MHz) in 25 kHz steps, with no frequency hopping capability, the radio below is a vehicle-mounted VHF-FM military tactical radio

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 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.

Frequency Band
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.

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 (using 150.0 Hz CTCSS squelch combined with channelization vs. "tuning" greatly simplified radio operation and made it easy for the average solider to use a radio with minimal training). 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. Tank radios with FM provided vast improvement over AM-based systems on the battlefield. 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.

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.

Personal tools