science

Output power of an analog TV transmitter

Output power of an analog TV transmitter 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 Output power of an analog TV transmitter rather than just read about it. In short: The output power of a TV transmitter is the electric power applied to antenna system. There are two definitions: nominal (or peak) and thermal.

Key takeaways

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

Reference excerpt

The output power of a TV transmitter is the electric power applied to antenna system. There are two definitions: nominal (or peak) and thermal. Analogue television systems put about 70% to 90% of the transmitters power into the sync pulses. The remainder of the transmitter's power goes into transmitting the video's higher frequencies and the FM audio carrier. Digital television modulation systems are about 30% more efficient than analogue modulation systems overall.

Analogue vs digital Analogue

The large amount of energy that Sync Pulses use is largely independent of the measurement system and efficiency of the analogue TV transmitter (as most analogue transmitters have on average 75% efficiency). The transmission of FM audio (including Stereo subcarriers) is only overall the 3rd largest consumer of TV transmitter power. Power consumption (most to least) : Sync Pulses, High Frequency Video, FM Audio, Vestigial AM Digital

DVB like transmission systems, with their groups of mathematically related carriers are not quite as energy efficient as 8VSB systems 8VSB transmission systems only provide a limited "Forced DC" signal (that consumes about 7% of the transmitters energy) that under multipath conditions can be lost causing a signal lock loss event

Power defined in terms of voltage The average power for a sinusoidal drive is

P = 1 T ∫ 0 T i ( t ) ⋅ e ( t ) d t . {\displaystyle P={\frac {1}{T}}\int _{0}^{T}i(t)\cdot e(t)dt\,\!.}

For a system where the voltage and the current are in phase, the output power can be given as

P = 1 T ⋅ R ∫ 0 T e ( t ) 2 d t . {\displaystyle P={\frac {1}{T\cdot R}}\int _{0}^{T}e(t)^{2}dt\,\!.}

In this equation R {\displaystyle R} is the resistance and e ( t ) {\displaystyle e(t)} is the output voltage

Nominal power of a TV transmitter Nominal power of a TV transmitter is given as the power during the sync interval. (For the sake of simplicity aural power is omitted) Since, the voltage during the sync interval is a fixed value,

P n = E p 2 2 ⋅ R {\displaystyle P_{n}={\frac {E_{p}^{2}}{2\cdot R}}\,\!}

P n = E 2 R {\displaystyle P_{n}={\frac {E^{2}}{R}}\,\!}

where E {\displaystyle E} is the rms value of the output voltage. To measure the nominal output power, measuring devices with time constants much greater than the line time are used. So the measuring equipment's measure only the highest level (sync pulse) of a line waveform which is 100%. This power level is the commercial power of the transmitter.

Thermal power In analogue TV broadcasting, the video signal modulates a carrier by a kind of amplitude modulation (VSB modulation or C3F). The modulation polarity is negative. That means that the higher the level of the video signal the lower the power of the RF signal. The lowest possible modulating signal during the synchrone interval yields 100% of the carrier. (The nominal power of the transmitter.) The blanking level (300 mV) yields 73% (in an ideally linear transmitter). Usually the figure 75% is found to be acceptable. The highest modulating signal at white (1000 mV) yields only 10% of the carrier. (so called residual carrier). Sometimes 12.5% is used as the residual carrier so the output power applied to the antenna system is considerably lower than the nominal power. The thermal power which can be measured by a microwave power meter depends on the program content as well as the residual carrier and sync depths.

Ratio of thermal power to nominal power Since the program content is variable, the thermal power varies during the transmission. However, for testing purposes a standard line waveform can be applied to the transmitter. Usually line waveforms corresponding to 350 mV or 300 mV black image (and without field sync) are applied to the input of the transmitter. For System B, the duration of the black level 300 mV (together with the front and back porches), is 59.3 μs and it corresponds to 73% of maximum voltage level. The duration of the sync pulse is 4.7 μs. The total duration of the line is 64 μs.

P t = E 2 64 ⋅ R ⋅ ( 4.7 ⋅ ( 100 % ) 2 + 59.3 ⋅ ( 73 % ) 2 ) ≈ 57 % ⋅ E 2 R {\displaystyle P_{t}={\frac {E^{2}}{64\cdot R}}\cdot (4.7\cdot (100\%)^{2}+59.3\cdot (73\%)^{2})\approx 57\%\cdot {\frac {E^{2}}{R}}\,\!}

… excerpt ends here. Continue reading the full article.

Worked examples

Example 1 — a first encounter with Output power of an analog TV transmitter

Start with the simplest possible case. Write down what Output power of an analog TV transmitter 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 Output power of an analog TV transmitter 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 Output power of an analog TV transmitter 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 Output power of an analog TV transmitter

In research: Output power of an analog TV transmitter 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 Output power of an analog TV transmitter 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: Output power of an analog TV transmitter is common in secondary-school and first-year university syllabi. It links to neighbouring topics Broadcast transmitters, Radio transmission power, Television technology, so understanding it makes those chapters shorter.
In everyday life: Look for Output power of an analog TV transmitter 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 Output power of an analog TV transmitter in 20 minutes

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Frequently asked questions

What is Output power of an analog TV transmitter in simple terms?

The output power of a TV transmitter is the electric power applied to antenna system. There are two definitions: nominal (or peak) and thermal.

Why does Output power of an analog TV transmitter 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 Output power of an analog TV transmitter?

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 Output power of an analog TV transmitter.