science

SCR-694

SCR-694 is a science 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 SCR-694 rather than just read about it. In short: The SCR-694 is a portable high frequency two way Signal Corps Radio used by the U.S. military during World War II. The SCR-694 provided transmission and reception of AM, MCW or CW radiotelegraphy within the frequency range of 3.8 to 6.5 MHz (78.89 to 46.12 m).

Key takeaways

SCR-694 belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect SCR-694 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of SCR-694 from memory before moving on to harder problems.

Reference excerpt

The SCR-694 is a portable high frequency two way Signal Corps Radio used by the U.S. military during World War II. The SCR-694 provided transmission and reception of AM, MCW or CW radiotelegraphy within the frequency range of 3.8 to 6.5 MHz (78.89 to 46.12 m). The radio set consists of the BC-1306 receiver and transmitter along with ancillary equipment, not all of which was required in every signal mission.

History

The SCR-694 began to replace the SCR-284 from mid 1944, with improved range and reduced weight (around half of its predecessor), though the latter continued to be used up until the end of the war. Designed to provide communication between moving or stationary vehicles or as a portable field radio, the SCR-694 was originally intended for use by mountain troops and airborne forces but soon became the Army-wide standard at battalion level. The SCR-694 saw use all over the army in many different theaters; notable instances include at regimental division headquarters during the Normandy invasion and the Cabanatuan prison raid as well as by scouts and reconnaissance units in the Pacific War. It was later replaced by the AN/GRC-9, which saw first documented use in the Korean war.

Specifications Weight Complete radio set: 191.5 pounds (86.9 kg). Set configured for dismounted operation: 108 lb (49 kg) BC-1306 with panel cover: 27 lb (12 kg) Transmitter — MOPA (master oscillator, power amplifier). Either of two crystal controlled master oscillator frequencies or operator tuning of master oscillator frequency may be selected. Suppressor grid modulation of the power amplifier is provided in radiotelephone and modulated continuous wave operation. Radio frequency (RF) power output 2 watts to 25 watts dependent on power switch setting, selected emission type and direct current (dc) power available at the power receptacle. Receiver — Single conversion superheterodyne, intermediate frequency 456 kilohertz. RF sensitivity in phone operation: 5 microvolts RF sensitivity in CW operation: 3 microvolts Selectivity: 3 to 6 kHz (99.93 to 49.97 km) Receiver frequency is independent of transmitter frequency. Range: Up to 15 miles (24 km) for phone operation Up to 30 miles (48 km) for CW between moving vehicle installations Power supply — The BC-1306 requires 400 to 500 volts direct current (VDC), 90 to 105 VDC, 6 VDC and 1.5 VDC. These voltages may be supplied by the GN-58 hand-cranked generator or the PE-237 Vibrator Power Unit, which may be operated from 6, 12 or 24 VDC. The receiver may be operated from dry battery BA-48. Partial list of additional components of the set — panel cover, mast sections for vertical antenna, wire antenna AN-160, spare parts, vehicle mount, mast bracket, mast base, telegraph key, crystal kit, headsets, microphones, electrical cords, bags, technical manual. Technical manual — TM 11-230C.

References

Notes TM 11-227 Signal Communication Directory. dated 10 April 1944 TM 11-487 Electrical Communication systems Equipment. dated 2 Oct. 1944

See also Signal Corps Radio SCR-300 backpack mounted unit SCR-536 handheld transceiver

External links https://web.archive.org/web/20090205221531/http://gordon.army.mil/OCOS/Museum/ScrComponents/scrPart4.asp SCR-694 in SCR list

Worked examples

Example 1 — a first encounter with SCR-694

Start with the simplest possible case. Write down what SCR-694 claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, 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 SCR-694 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 SCR-694 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 SCR-694

In research: SCR-694 appears in science 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 SCR-694 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: SCR-694 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Amateur radio transmitters, Military electronics of the United States, Radio systems of the United States Army, so understanding it makes those chapters shorter.
In everyday life: Look for SCR-694 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 SCR-694 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what SCR-694 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 SCR-694 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is SCR-694 in simple terms?

Why does SCR-694 matter?

Because it connects several science 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 SCR-694?

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 SCR-694.