physics

Survivable Low Frequency Communications System

Survivable Low Frequency Communications System is a physics topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Survivable Low Frequency Communications System rather than just read about it. In short: The AN/FRC-117 Survivable Low Frequency Communications System (SLFCS) was a communications system designed to be able to operate, albeit at low data transfer rates, during and after a nuclear attack. The system used both very low frequency (VLF), and low frequency (LF) radio bands.

Key takeaways

Survivable Low Frequency Communications System belongs to physics; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Survivable Low Frequency Communications System to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Survivable Low Frequency Communications System from memory before moving on to harder problems.

Reference excerpt

The AN/FRC-117 Survivable Low Frequency Communications System (SLFCS) was a communications system designed to be able to operate, albeit at low data transfer rates, during and after a nuclear attack. The system used both very low frequency (VLF), and low frequency (LF) radio bands.

Mission SLFCS was used for United States nuclear forces' command and control communications for Emergency Action Message dissemination and force direction. Single channel, receive only capability was provided at ICBM launch control centers. The single channel operated between 14 kHz and 60 kHz to receive commands from remotely located Combat Operations Center – Transmit/Receive (T/R) sites; this low frequency range is only slightly affected by nuclear blasts. For example, the Silver Creek site typically transmitted at 34.5 kHz. The transmitter could be tuned to any designated frequency in the above mentioned range. Receivers could receive down to 14.0 kHz. SLFCS' primary advantage was that it would experience minimal radio signal degradation as a result of nuclear detonations. It would be an alternate means of communication during and after detonations, providing a survivable command and control communications network for the Strategic Air Command (SAC), the Joint Chiefs of Staff (JCS), and North American Aerospace Defense Command (NORAD). SLFCS would also relay signals from the Navy's LF/VLF systems.

Locations

Transmitters Silver Creek, Nebraska (Detachment 1, 1st Aerospace Communications Group) Hawes Air Force Station, California (Detachment 2, 33rd Communications Squadron) PACCS aircraft NAOC (formerly known as NEACP)

GREEN PINE Stations

The GREEN PINE communication system took messages broadcast over SLFCS and 'upconverted' them to UHF messages for bombers headed north. There were a handful of GREEN PINE stations in the northern portions of Alaska and Canada.

Receive Only Altus AFB, Oklahoma Barksdale AFB, Louisiana (8th Air Force Command Post) Beale AFB, California (9 SRW Command Post) Blytheville AFB, Arkansas (97 BW Command Post) CLOSED Carswell AFB, Texas (7 BW Command Post) CLOSED Castle AFB, California (93 BW Command Post) CLOSED Davis-Monthan AFB, Arizona - 390th SMW (18 LCCs) CLOSED Dyess AFB, Texas (96 BW Command Post) Eielson AFB, Alaska (6 SW Command Post) Ellsworth AFB, South Dakota - 44th SMW (16 terminals - 15 LCCs and Wing Command Post) CLOSED Fairchild AFB, Washington F.E. Warren AFB, Wyoming - 90th Missile Wing, 20th Air Force (21 terminals- 20 LCCs, 1 at 20th AF Missile Operations Center) Grand Forks AFB, North Dakota - 321st SMW (16 terminals - 15 LCCs and Wing Command Post) CLOSED Griffiss AFB, New York CLOSED Grissom AFB, Indiana K.I. Sawyer AFB, Michigan CLOSED Little Rock AFB, Arkansas - 308th SMW (18 LCCs) CLOSED Loring AFB, Maine (42 BW Command Post) CLOSED Luke AFB, Arizona Rickenbacker AFB, Ohio Malmstrom AFB, Montana 341st SMW (20 terminals - 20 LCCs) Mather AFB, California CLOSED McConnell AFB, Kansas 22 BW (Command Post), 381st SMW (18 LCCs) CLOSED Minot AFB, North Dakota (5 BW/91 SMW 15 LCCs) Pease AFB, New Hampshire (509 BW Command Post) CLOSED Plattsburgh AFB, New York (380 BW Command Post) CLOSED Robins AFB, Georgia (19 BW Command Post) Seymour Johnson AFB, North Carolina (68 BW Command Post) Travis AFB, California Vandenberg AFB, California (1 STRAD Command Post)1 LCC O1A Whiteman AFB, Missouri - 351st SMW (16 terminals - 15 LCCs and Wing Command Post) CLOSED Wurtsmith AFB, Michigan CLOSED March AFB, California (15th AF COC)

History The first program (487L) took six years from the time of the initial requirement to full operation. The second part (616A), which was basically a modification of an already operational system, took 10 years.

Chronology 1961 29 Sep – Headquarters USAF issues Specific Operating Requirement 193, for the Survivable Low Frequency Communications System; system is envisioned to link Alternate Joint Command Center with command centers of SAC, NORAD, SAC numbered air forces with LF radio networks; a total of 18 transmit/receive (T/R) sites and 375 LF-receive only (R/O) in all SAC launch facilities, mobile Minuteman trains, SAC air base control rooms, and SAC UHF positive control stations in the northern tier 1962 12 Mar – Amendment to SOR 193 changes number of transmit T/R sites to 19 (three each at AJCC, SAC, NORAD, two each at 2d Air Force, 15th Air Force and 8th Air Force, one each at Larson AFB, Southern Alaska, Sondrestrom AB, and the United Kingdom; Full Operating Capability was extended from July 1964 to May 1965. 27 Apr – A revised program directive delineated the network; T/R equipment would be installed at HQ SAC, the SAC numbered air force headquarters, and in the ABNCP, Alternate Joint Command Center (AJCC) and NORAD command center. 14 Green Pine stations, missile launch control centers, all SAC bomber wing command posts would have R/O terminals, as would the NORAD regional control centers. Initial Operating Capability (IOC) was placed at 1 Oct 1966. 1968 29 Jul 1968 – Silver Creek site accepted by SAC 19 Aug 1968 – Silver Creek site turned on for continuous operation 5 Sep 1968 – Silver Creek begins operational testing 1971 16 Jun – SLFCS IOC obtained by SAC units 1974 26 Jul – HQ USAF approves Program 616A (Improved SLFCS); system would improve SLFCS by providing anti-jam protection, improved modems, increased range and make it compatible with the Navy LF/VLF system 1978 SAC conducts Initial Operational Test and Evaluation (IOT&E) at Ellsworth AFB, South Dakota for Program 616A; test is successful 1986 30 Sep – deactivation of Hawes Radio Relay Site, Hinkley, California 20 Oct – destruction of Hawes Radio Relay Site by the Army Corps of Engineers 1996 Rapid Execution and Combat Targeting (REACT) upgrade to Minuteman launch control centers complete; advances allow SLFCS messages to be handled automatically by Higher Authority Communications/Rapid Message Processing Element (HAC/RMPE) 2005 11 Nov – last Minuteman Launch Control Center receives Minimum Essential Emergency Communications Network (MEECN) upgrade, rendering SLFCS obsolete. 2010 MMP – Minuteman Minimum Essential Emergency Communications Network Program now in the upgrade portion. Work In Progress. Advanced EHF will be available once upgrade is complete.

Photo gallery

Illustrations

Worked examples

Example 1 — a first encounter with Survivable Low Frequency Communications System

Start with the simplest possible case. Write down what Survivable Low Frequency Communications System claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In physics, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Survivable Low Frequency Communications System before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Survivable Low Frequency Communications System ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Survivable Low Frequency Communications System

In research: Survivable Low Frequency Communications System appears in physics research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Survivable Low Frequency Communications System in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Survivable Low Frequency Communications System is common in secondary-school and first-year university syllabi. It links to neighbouring topics Military communications of the United States, Military radio systems of the United States, Nuclear warfare, so understanding it makes those chapters shorter.
In everyday life: Look for Survivable Low Frequency Communications System outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Survivable Low Frequency Communications System in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Survivable Low Frequency Communications System means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Survivable Low Frequency Communications System out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Survivable Low Frequency Communications System in simple terms?

Why does Survivable Low Frequency Communications System matter?

Because it connects several physics ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Survivable Low Frequency Communications System?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Survivable Low Frequency Communications System.