# Lesson 33 Flashcards

Click a question to reveal the answer.

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<summary><strong>1. What two conditions must be met for successful communication?</strong></summary>
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- Line-of-sight (LOS)
- Sufficient received power (or SNR above threshold)

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<summary><strong>2. What does the Friis equation calculate?</strong></summary>
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The received power at the antenna.

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<summary><strong>3. Write the Friis equation.</strong></summary>
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$$
P_R = P_T G_T G_R \frac{\lambda^2}{(4\pi R)^2}
$$

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<summary><strong>4. What happens to received power if distance doubles?</strong></summary>
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It decreases by a factor of 4.

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<summary><strong>5. What happens to received power if transmitted power doubles?</strong></summary>
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It doubles.

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<summary><strong>6. How do antenna gains affect received power?</strong></summary>
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They increase received power linearly.

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<summary><strong>7. What is the relationship between frequency and wavelength?</strong></summary>
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$$
\lambda = \frac{c}{f}
$$

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<summary><strong>8. Why do lower frequencies travel farther?</strong></summary>
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They have longer wavelengths, which increases received power.

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<summary><strong>9. What units must distance be in when using the Friis equation?</strong></summary>
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Meters.

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<summary><strong>10. What is SNR?</strong></summary>
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The ratio of signal power to noise power.

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<summary><strong>11. Write the SNR equation.</strong></summary>
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$$
SNR = \frac{P_{signal}}{P_{noise}}
$$

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<summary><strong>12. Write the thermal noise equation.</strong></summary>
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$$
P_{noise} = k T_{sys} BW
$$

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<summary><strong>13. What increases noise power?</strong></summary>
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- Higher temperature
- Larger bandwidth

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<summary><strong>14. What is a decibel (dB)?</strong></summary>
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A logarithmic representation of a power ratio.

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<summary><strong>15. Write the decibel equation.</strong></summary>
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$$
G_{dB} = 10 \log_{10}(G)
$$

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