science

Pilot signal

Pilot signal 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 Pilot signal rather than just read about it. In short: In telecommunications, a pilot signal is a signal, usually a single frequency, transmitted over a communications system for supervisory, control, equalization, continuity, synchronization, or reference purposes. Uses in different communication systems FM Radio In FM stereo broadcasting, a pilot tone of 19 kHz indicates that there is stereophonic information at 38 kHz (the second harmonic of the pilot tone).

Key takeaways

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

Reference excerpt

Uses in different communication systems

FM Radio In FM stereo broadcasting, a pilot tone of 19 kHz indicates that there is stereophonic information at 38 kHz (the second harmonic of the pilot tone). The receiver doubles the frequency of the pilot tone and uses it as a frequency and phase reference to demodulate the stereo information.

If no 19 kHz pilot tone is present, then any signals in the 23–53 kHz range are ignored by a stereo receiver. A guard band of ±4 kHz (15–23 kHz) protects the pilot tone from interference from the baseband audio signal (50 Hz–15 kHz) and from the lower sideband of the double sideband stereo information (23–53 kHz). The third harmonic of the pilot (57 kHz) is used for Radio Data System. The fourth harmonic (76 kHz) is used for Data Radio Channel.

AM Radio In AM stereo, the bandwidth is too narrow to accommodate subcarriers, so the modulation itself is changed, and the pilot tone is infrasonic (below the normal hearing range, instead of above it) at a frequency of 25 Hz.

Television In some color television standards, the color burst placed after every sync pulse on visible lines (as done in PAL and NTSC) is the pilot signal to indicate that there are color subcarriers present and allow synchronizing the phase of the local oscillator in the demodulation circuitry. However, SECAM features continuous subcarriers which don't need their phase tracked due to being frequency-modulated as compared to the QAM approach of the other systems, thus making it unnecessary. In the NTSC television system, a pilot tone of 9⁄572 MHz (15,734.27 Hz) is used to indicate the presence of MTS stereo.

Video Recording In some analog video formats frequency modulation is the standard method for recording the luminance part of the signal, and is used to record a composite video signal in direct color systems, e.g. Video 2000 and some Hi-band formats a pilot tone is added to the signal to detect and correct timebase errors.

Cable In cable service plant infrastructures, two or more pilot frequencies are used to allow network amplifiers to automatically adjust their gain over temperature swings. This is done by the amplifiers having special circuitry that track the frequencies in order to maintain a consistent gain. Without this capability, network amplifiers may drive the signal too strongly or weakly, thus requiring constant adjustment. Pilot frequencies can be generated by an agile modulator, taking the space of analog NTSC channels, or by dedicated equipment. Sometimes it is necessary to employ several independent pilot frequencies. Most radio relay systems use radio or continuity pilots of their own but transmit also the pilot frequencies belonging to the carrier frequency multiplex system.

See also Syncword Synchronous Idle Pilottone

References This article incorporates public domain material from Federal Standard 1037C. General Services Administration. Archived from the original on 2022-01-22. (in support of MIL-STD-188).

Illustrations

Worked examples

Example 1 — a first encounter with Pilot signal

Start with the simplest possible case. Write down what Pilot signal 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 Pilot signal 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 Pilot signal 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 Pilot signal

In research: Pilot signal 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 Pilot signal 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: Pilot signal is common in secondary-school and first-year university syllabi. It links to neighbouring topics Synchronization, Telecommunications techniques, so understanding it makes those chapters shorter.
In everyday life: Look for Pilot signal 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.

Ask Teacher Smith questions about this articleOpens your AI tutor with a question about “Pilot signal” →

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study Pilot signal in 20 minutes

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

Frequently asked questions

What is Pilot signal in simple terms?

In telecommunications, a pilot signal is a signal, usually a single frequency, transmitted over a communications system for supervisory, control, equalization, continuity, synchronization, or reference purposes. Uses in different communication systems FM Radio In FM stereo broadcasting, a pilot ton…

Why does Pilot signal 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 Pilot signal?

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 Pilot signal.