# Extra Questions **URL:** https://forum.openhamprep.com/c/extra-questions/9.md [Latest](https://forum.openhamprep.com/latest.md) · [Categories](https://forum.openhamprep.com/categories.md) · [Tags](https://forum.openhamprep.com/tags.md) --- ## [About the Extra Questions category](https://forum.openhamprep.com/t/about-the-extra-questions-category/14)
**Author:** [@system](https://forum.openhamprep.com/u/system)\ **Replies:** 0\ **Last updated:** [December 15, 2025, 1:17am UTC](https://forum.openhamprep.com/t/about-the-extra-questions-category/14 "2025-12-15T01:17:51Z")
The official US Amateur Extra class question pool, with explanations. Post your requests for help, additional explanation, or suggestions for changes to explanations by clicking “Reply” at the bottom of any question. Fo… --- ## [E7B08 - Why are switching amplifiers more efficient than linear amplifiers?](https://forum.openhamprep.com/t/e7b08-why-are-switching-amplifiers-more-efficient-than-linear-amplifiers/1362)
**Author:** [@system](https://forum.openhamprep.com/u/system)\ **Replies:** 1\ **Last updated:** [January 24, 2026, 8:01pm UTC](https://forum.openhamprep.com/t/e7b08-why-are-switching-amplifiers-more-efficient-than-linear-amplifiers/1362 "2026-01-24T20:01:37Z")
Question Why are switching amplifiers more efficient than linear amplifiers? Answer Options A) Switching amplifiers operate at higher voltages B) The switching device is at saturation or cutoff most of the time C) Line… --- ## [E8A01 - What technique shows that a square wave is made up of a sine wave and its odd harmonics?](https://forum.openhamprep.com/t/e8a01-what-technique-shows-that-a-square-wave-is-made-up-of-a-sine-wave-and-its-odd-harmonics/405)
**Author:** [@system](https://forum.openhamprep.com/u/system)\ **Replies:** 1\ **Last updated:** [January 24, 2026, 7:31pm UTC](https://forum.openhamprep.com/t/e8a01-what-technique-shows-that-a-square-wave-is-made-up-of-a-sine-wave-and-its-odd-harmonics/405 "2026-01-24T19:31:56Z")
Question What technique shows that a square wave is made up of a sine wave and its odd harmonics? Answer Options A) Fourier analysis B) Vector analysis C) Numerical analysis D) Differential analysis Correct Answer: A … --- ## [E2A13 - Which of the following techniques is used by digital satellites to relay messages?](https://forum.openhamprep.com/t/e2a13-which-of-the-following-techniques-is-used-by-digital-satellites-to-relay-messages/1008)
**Author:** [@system](https://forum.openhamprep.com/u/system)\ **Replies:** 1\ **Last updated:** [January 2, 2026, 11:56pm UTC](https://forum.openhamprep.com/t/e2a13-which-of-the-following-techniques-is-used-by-digital-satellites-to-relay-messages/1008 "2026-01-02T23:56:54Z")
Question Which of the following techniques is used by digital satellites to relay messages? Answer Options A) Digipeating B) Store-and-forward C) Multisatellite relaying D) Node hopping Correct Answer: B Explanation … --- ## [E6D07 - What is the current that flows in the primary winding of a transformer when there is no load on the secondary winding?](https://forum.openhamprep.com/t/e6d07-what-is-the-current-that-flows-in-the-primary-winding-of-a-transformer-when-there-is-no-load-on-the-secondary-winding/1261)
**Author:** [@system](https://forum.openhamprep.com/u/system)\ **Replies:** 1\ **Last updated:** [January 2, 2026, 11:55pm UTC](https://forum.openhamprep.com/t/e6d07-what-is-the-current-that-flows-in-the-primary-winding-of-a-transformer-when-there-is-no-load-on-the-secondary-winding/1261 "2026-01-02T23:55:39Z")
Question What is the current that flows in the primary winding of a transformer when there is no load on the secondary winding? Answer Options A) Stabilizing current B) Direct current C) Excitation current D) Magnetizi… --- ## [E7H13 - Which of the following is a technique for providing highly accurate and stable oscillators needed for microwave transmission and reception?](https://forum.openhamprep.com/t/e7h13-which-of-the-following-is-a-technique-for-providing-highly-accurate-and-stable-oscillators-needed-for-microwave-transmission-and-reception/1435)
**Author:** [@system](https://forum.openhamprep.com/u/system)\ **Replies:** 0\ **Last updated:** [January 2, 2026, 7:54pm UTC](https://forum.openhamprep.com/t/e7h13-which-of-the-following-is-a-technique-for-providing-highly-accurate-and-stable-oscillators-needed-for-microwave-transmission-and-reception/1435 "2026-01-02T19:54:19Z")
Question Which of the following is a technique for providing highly accurate and stable oscillators needed for microwave transmission and reception? Answer Options A) Use a GPS signal reference B) Use a rubidium stabil… --- ## [E7H12 - Which of the following ensures that a crystal oscillator operates on the frequency specified by the crystal manufacturer?](https://forum.openhamprep.com/t/e7h12-which-of-the-following-ensures-that-a-crystal-oscillator-operates-on-the-frequency-specified-by-the-crystal-manufacturer/1434)
**Author:** [@system](https://forum.openhamprep.com/u/system)\ **Replies:** 0\ **Last updated:** [January 2, 2026, 7:54pm UTC](https://forum.openhamprep.com/t/e7h12-which-of-the-following-ensures-that-a-crystal-oscillator-operates-on-the-frequency-specified-by-the-crystal-manufacturer/1434 "2026-01-02T19:54:19Z")
Question Which of the following ensures that a crystal oscillator operates on the frequency specified by the crystal manufacturer? Answer Options A) Provide the crystal with a specified parallel inductance B) Provide t… --- ## [E7H11 - What are the major spectral impurity components of direct digital synthesizers?](https://forum.openhamprep.com/t/e7h11-what-are-the-major-spectral-impurity-components-of-direct-digital-synthesizers/1433)
**Author:** [@system](https://forum.openhamprep.com/u/system)\ **Replies:** 0\ **Last updated:** [January 2, 2026, 7:54pm UTC](https://forum.openhamprep.com/t/e7h11-what-are-the-major-spectral-impurity-components-of-direct-digital-synthesizers/1433 "2026-01-02T19:54:19Z")
Question What are the major spectral impurity components of direct digital synthesizers? Answer Options A) Broadband noise B) Digital conversion noise C) Spurious signals at discrete frequencies D) Harmonics of the loc… --- ## [E7H10 - What information is contained in the lookup table of a direct digital synthesizer (DDS)?](https://forum.openhamprep.com/t/e7h10-what-information-is-contained-in-the-lookup-table-of-a-direct-digital-synthesizer-dds/1432)
**Author:** [@system](https://forum.openhamprep.com/u/system)\ **Replies:** 0\ **Last updated:** [January 2, 2026, 7:54pm UTC](https://forum.openhamprep.com/t/e7h10-what-information-is-contained-in-the-lookup-table-of-a-direct-digital-synthesizer-dds/1432 "2026-01-02T19:54:18Z")
Question What information is contained in the lookup table of a direct digital synthesizer (DDS)? Answer Options A) The phase relationship between a reference oscillator and the output waveform B) Amplitude values that… --- ## [E7H09 - What type of frequency synthesizer circuit uses a phase accumulator, lookup table, digital-to-analog converter, and a low-pass anti-alias filter?](https://forum.openhamprep.com/t/e7h09-what-type-of-frequency-synthesizer-circuit-uses-a-phase-accumulator-lookup-table-digital-to-analog-converter-and-a-low-pass-anti-alias-filter/1431)
**Author:** [@system](https://forum.openhamprep.com/u/system)\ **Replies:** 0\ **Last updated:** [January 2, 2026, 7:54pm UTC](https://forum.openhamprep.com/t/e7h09-what-type-of-frequency-synthesizer-circuit-uses-a-phase-accumulator-lookup-table-digital-to-analog-converter-and-a-low-pass-anti-alias-filter/1431 "2026-01-02T19:54:18Z")
Question What type of frequency synthesizer circuit uses a phase accumulator, lookup table, digital-to-analog converter, and a low-pass anti-alias filter? Answer Options A) A direct digital synthesizer B) A hybrid synt… --- ## [E7H08 - Which of the following components can be used to reduce thermal drift in crystal oscillators?](https://forum.openhamprep.com/t/e7h08-which-of-the-following-components-can-be-used-to-reduce-thermal-drift-in-crystal-oscillators/1430)
**Author:** [@system](https://forum.openhamprep.com/u/system)\ **Replies:** 0\ **Last updated:** [January 2, 2026, 7:54pm UTC](https://forum.openhamprep.com/t/e7h08-which-of-the-following-components-can-be-used-to-reduce-thermal-drift-in-crystal-oscillators/1430 "2026-01-02T19:54:17Z")
Question Which of the following components can be used to reduce thermal drift in crystal oscillators? Answer Options A) NPO capacitors B) Toroidal inductors C) Wirewound resistors D) Non-inductive resistors Correct A… --- ## [E7H07 - How can an oscillator's microphonic responses be reduced?](https://forum.openhamprep.com/t/e7h07-how-can-an-oscillators-microphonic-responses-be-reduced/1429)
**Author:** [@system](https://forum.openhamprep.com/u/system)\ **Replies:** 0\ **Last updated:** [January 2, 2026, 7:53pm UTC](https://forum.openhamprep.com/t/e7h07-how-can-an-oscillators-microphonic-responses-be-reduced/1429 "2026-01-02T19:53:32Z")
Question How can an oscillator’s microphonic responses be reduced? Answer Options A) Use NPO capacitors B) Reduce noise on the oscillator’s power supply C) Increase the gain D) Mechanically isolate the oscillator circu… --- ## [E7H06 - Which of these functions can be performed by a phase-locked loop?](https://forum.openhamprep.com/t/e7h06-which-of-these-functions-can-be-performed-by-a-phase-locked-loop/1428)
**Author:** [@system](https://forum.openhamprep.com/u/system)\ **Replies:** 0\ **Last updated:** [January 2, 2026, 7:53pm UTC](https://forum.openhamprep.com/t/e7h06-which-of-these-functions-can-be-performed-by-a-phase-locked-loop/1428 "2026-01-02T19:53:31Z")
Question Which of these functions can be performed by a phase-locked loop? Answer Options A) Wide-band AF and RF power amplification B) Frequency synthesis and FM demodulation C) Photovoltaic conversion and optical cou… --- ## [E7H05 - How is positive feedback supplied in a Pierce oscillator?](https://forum.openhamprep.com/t/e7h05-how-is-positive-feedback-supplied-in-a-pierce-oscillator/1427)
**Author:** [@system](https://forum.openhamprep.com/u/system)\ **Replies:** 0\ **Last updated:** [January 2, 2026, 7:53pm UTC](https://forum.openhamprep.com/t/e7h05-how-is-positive-feedback-supplied-in-a-pierce-oscillator/1427 "2026-01-02T19:53:31Z")
Question How is positive feedback supplied in a Pierce oscillator? Answer Options A) Through a tapped coil B) Through link coupling C) Through a neutralizing capacitor D) Through a quartz crystal Correct Answer: D E… --- ## [E7H04 - How is positive feedback supplied in a Colpitts oscillator?](https://forum.openhamprep.com/t/e7h04-how-is-positive-feedback-supplied-in-a-colpitts-oscillator/1426)
**Author:** [@system](https://forum.openhamprep.com/u/system)\ **Replies:** 0\ **Last updated:** [January 2, 2026, 7:53pm UTC](https://forum.openhamprep.com/t/e7h04-how-is-positive-feedback-supplied-in-a-colpitts-oscillator/1426 "2026-01-02T19:53:30Z")
Question How is positive feedback supplied in a Colpitts oscillator? Answer Options A) Through a tapped coil B) Through link coupling C) Through a capacitive divider D) Through a neutralizing capacitor Correct Answer:… --- ## [E7H03 - What is a phase-locked loop?](https://forum.openhamprep.com/t/e7h03-what-is-a-phase-locked-loop/1425)
**Author:** [@system](https://forum.openhamprep.com/u/system)\ **Replies:** 0\ **Last updated:** [January 2, 2026, 7:53pm UTC](https://forum.openhamprep.com/t/e7h03-what-is-a-phase-locked-loop/1425 "2026-01-02T19:53:29Z")
Question What is a phase-locked loop? Answer Options A) An electronic servo loop consisting of a ratio detector, reactance modulator, and voltage-controlled oscillator B) An electronic circuit also known as a monostabl… --- ## [E7H02 - What is a microphonic?](https://forum.openhamprep.com/t/e7h02-what-is-a-microphonic/1424)
**Author:** [@system](https://forum.openhamprep.com/u/system)\ **Replies:** 0\ **Last updated:** [January 2, 2026, 7:53pm UTC](https://forum.openhamprep.com/t/e7h02-what-is-a-microphonic/1424 "2026-01-02T19:53:28Z")
Question What is a microphonic? Answer Options A) An IC used for amplifying microphone signals B) Distortion caused by RF pickup on the microphone cable C) Changes in oscillator frequency caused by mechanical vibration … --- ## [E7H01 - What are three common oscillator circuits?](https://forum.openhamprep.com/t/e7h01-what-are-three-common-oscillator-circuits/1423)
**Author:** [@system](https://forum.openhamprep.com/u/system)\ **Replies:** 0\ **Last updated:** [January 2, 2026, 7:53pm UTC](https://forum.openhamprep.com/t/e7h01-what-are-three-common-oscillator-circuits/1423 "2026-01-02T19:53:28Z")
Question What are three common oscillator circuits? Answer Options A) Taft, Pierce, and negative feedback B) Pierce, Fenner, and Beane C) Taft, Hartley, and Pierce D) Colpitts, Hartley, and Pierce Correct Answer: D E… --- ## [E7G12 - What is an operational amplifier?](https://forum.openhamprep.com/t/e7g12-what-is-an-operational-amplifier/1422)
**Author:** [@system](https://forum.openhamprep.com/u/system)\ **Replies:** 0\ **Last updated:** [January 2, 2026, 7:53pm UTC](https://forum.openhamprep.com/t/e7g12-what-is-an-operational-amplifier/1422 "2026-01-02T19:53:27Z")
Question What is an operational amplifier? Answer Options A) A high-gain, direct-coupled differential amplifier with very high input impedance and very low output impedance B) A digital audio amplifier whose characteri… --- ## [E7G11 - What absolute voltage gain can be expected from the circuit in Figure E7-3 when R1 is 3,300 ohms and RF is 47 kilohms?](https://forum.openhamprep.com/t/e7g11-what-absolute-voltage-gain-can-be-expected-from-the-circuit-in-figure-e7-3-when-r1-is-3-300-ohms-and-rf-is-47-kilohms/1421)
**Author:** [@system](https://forum.openhamprep.com/u/system)\ **Replies:** 0\ **Last updated:** [January 2, 2026, 7:53pm UTC](https://forum.openhamprep.com/t/e7g11-what-absolute-voltage-gain-can-be-expected-from-the-circuit-in-figure-e7-3-when-r1-is-3-300-ohms-and-rf-is-47-kilohms/1421 "2026-01-02T19:53:27Z")
Question What absolute voltage gain can be expected from the circuit in Figure E7-3 when R1 is 3,300 ohms and RF is 47 kilohms? Answer Options A) 28 B) 14 C) 7 D) 0.07 Correct Answer: B Explanation The voltage ga… --- ## [E7G09 - What will be the output voltage of the circuit shown in Figure E7-3 if R1 is 1,000 ohms, RF is 10,000 ohms, and 0.23 volts DC is applied to the input?](https://forum.openhamprep.com/t/e7g09-what-will-be-the-output-voltage-of-the-circuit-shown-in-figure-e7-3-if-r1-is-1-000-ohms-rf-is-10-000-ohms-and-0-23-volts-dc-is-applied-to-the-input/1420)
**Author:** [@system](https://forum.openhamprep.com/u/system)\ **Replies:** 0\ **Last updated:** [January 2, 2026, 7:53pm UTC](https://forum.openhamprep.com/t/e7g09-what-will-be-the-output-voltage-of-the-circuit-shown-in-figure-e7-3-if-r1-is-1-000-ohms-rf-is-10-000-ohms-and-0-23-volts-dc-is-applied-to-the-input/1420 "2026-01-02T19:53:27Z")
Question What will be the output voltage of the circuit shown in Figure E7-3 if R1 is 1,000 ohms, RF is 10,000 ohms, and 0.23 volts DC is applied to the input? Answer Options A) 0.23 volts B) 2.3 volts C) -0.23 volt… --- ## [E7G08 - How does the gain of an ideal operational amplifier vary with frequency?](https://forum.openhamprep.com/t/e7g08-how-does-the-gain-of-an-ideal-operational-amplifier-vary-with-frequency/1419)
**Author:** [@system](https://forum.openhamprep.com/u/system)\ **Replies:** 0\ **Last updated:** [January 2, 2026, 7:53pm UTC](https://forum.openhamprep.com/t/e7g08-how-does-the-gain-of-an-ideal-operational-amplifier-vary-with-frequency/1419 "2026-01-02T19:53:26Z")
Question How does the gain of an ideal operational amplifier vary with frequency? Answer Options A) It increases linearly with increasing frequency B) It decreases linearly with increasing frequency C) It decreases log… --- ## [E7G07 - What voltage gain can be expected from the circuit in Figure E7-3 when R1 is 10 ohms and RF is 470 ohms?](https://forum.openhamprep.com/t/e7g07-what-voltage-gain-can-be-expected-from-the-circuit-in-figure-e7-3-when-r1-is-10-ohms-and-rf-is-470-ohms/1418)
**Author:** [@system](https://forum.openhamprep.com/u/system)\ **Replies:** 0\ **Last updated:** [January 2, 2026, 7:53pm UTC](https://forum.openhamprep.com/t/e7g07-what-voltage-gain-can-be-expected-from-the-circuit-in-figure-e7-3-when-r1-is-10-ohms-and-rf-is-470-ohms/1418 "2026-01-02T19:53:26Z")
Question What voltage gain can be expected from the circuit in Figure E7-3 when R1 is 10 ohms and RF is 470 ohms? Answer Options A) 0.21 B) 4700 C) 47 D) 24 Correct Answer: C Explanation Figure E7-3 shows an inv… --- ## [E7G06 - What is the gain-bandwidth of an operational amplifier?](https://forum.openhamprep.com/t/e7g06-what-is-the-gain-bandwidth-of-an-operational-amplifier/1417)
**Author:** [@system](https://forum.openhamprep.com/u/system)\ **Replies:** 0\ **Last updated:** [January 2, 2026, 7:53pm UTC](https://forum.openhamprep.com/t/e7g06-what-is-the-gain-bandwidth-of-an-operational-amplifier/1417 "2026-01-02T19:53:25Z")
Question What is the gain-bandwidth of an operational amplifier? Answer Options A) The maximum frequency for a filter circuit using that type of amplifier B) The frequency at which the open-loop gain of the amplifier e… --- ## [E7G05 - How can unwanted ringing and audio instability be prevented in an op-amp audio filter?](https://forum.openhamprep.com/t/e7g05-how-can-unwanted-ringing-and-audio-instability-be-prevented-in-an-op-amp-audio-filter/1416)
**Author:** [@system](https://forum.openhamprep.com/u/system)\ **Replies:** 0\ **Last updated:** [January 2, 2026, 7:53pm UTC](https://forum.openhamprep.com/t/e7g05-how-can-unwanted-ringing-and-audio-instability-be-prevented-in-an-op-amp-audio-filter/1416 "2026-01-02T19:53:25Z")
Question How can unwanted ringing and audio instability be prevented in an op-amp audio filter? Answer Options A) Restrict both gain and Q B) Restrict gain but increase Q C) Restrict Q but increase gain D) Increase bot… --- ## [E7G04 - What is meant by the term "op-amp input offset voltage"?](https://forum.openhamprep.com/t/e7g04-what-is-meant-by-the-term-op-amp-input-offset-voltage/1415)
**Author:** [@system](https://forum.openhamprep.com/u/system)\ **Replies:** 0\ **Last updated:** [January 2, 2026, 7:53pm UTC](https://forum.openhamprep.com/t/e7g04-what-is-meant-by-the-term-op-amp-input-offset-voltage/1415 "2026-01-02T19:53:24Z")
Question What is meant by the term “op-amp input offset voltage”? Answer Options A) The output voltage of the op-amp minus its input voltage B) The difference between the output voltage of the op-amp and the input volt… --- ## [E7G03 - What is the typical input impedance of an op-amp?](https://forum.openhamprep.com/t/e7g03-what-is-the-typical-input-impedance-of-an-op-amp/1414)
**Author:** [@system](https://forum.openhamprep.com/u/system)\ **Replies:** 0\ **Last updated:** [January 2, 2026, 7:53pm UTC](https://forum.openhamprep.com/t/e7g03-what-is-the-typical-input-impedance-of-an-op-amp/1414 "2026-01-02T19:53:24Z")
Question What is the typical input impedance of an op-amp? Answer Options A) 100 ohms B) 10,000 ohms C) Very low D) Very high Correct Answer: D Explanation An operational amplifier (\\text{op-amp}) is a differential … --- ## [E7G02 - What is the frequency response of the circuit in E7-3 if a capacitor is added across the feedback resistor?](https://forum.openhamprep.com/t/e7g02-what-is-the-frequency-response-of-the-circuit-in-e7-3-if-a-capacitor-is-added-across-the-feedback-resistor/1413)
**Author:** [@system](https://forum.openhamprep.com/u/system)\ **Replies:** 0\ **Last updated:** [January 2, 2026, 7:53pm UTC](https://forum.openhamprep.com/t/e7g02-what-is-the-frequency-response-of-the-circuit-in-e7-3-if-a-capacitor-is-added-across-the-feedback-resistor/1413 "2026-01-02T19:53:24Z")
Question What is the frequency response of the circuit in E7-3 if a capacitor is added across the feedback resistor? Answer Options A) High-pass filter B) Low-pass filter C) Band-pass filter D) Notch filter Correct… --- ## [E7G01 - What is the typical output impedance of an op-amp?](https://forum.openhamprep.com/t/e7g01-what-is-the-typical-output-impedance-of-an-op-amp/1412)
**Author:** [@system](https://forum.openhamprep.com/u/system)\ **Replies:** 0\ **Last updated:** [January 2, 2026, 7:53pm UTC](https://forum.openhamprep.com/t/e7g01-what-is-the-typical-output-impedance-of-an-op-amp/1412 "2026-01-02T19:53:23Z")
Question What is the typical output impedance of an op-amp? Answer Options A) Very low B) Very high C) 100 ohms D) 10,000 ohms Correct Answer: A Explanation An operational amplifier (\\text{op-amp}) is designed to be… --- ## [E7F14 - Which of the following would allow a digital signal processing filter to create a sharper filter response?](https://forum.openhamprep.com/t/e7f14-which-of-the-following-would-allow-a-digital-signal-processing-filter-to-create-a-sharper-filter-response/1411)
**Author:** [@system](https://forum.openhamprep.com/u/system)\ **Replies:** 0\ **Last updated:** [January 2, 2026, 7:53pm UTC](https://forum.openhamprep.com/t/e7f14-which-of-the-following-would-allow-a-digital-signal-processing-filter-to-create-a-sharper-filter-response/1411 "2026-01-02T19:53:23Z")
Question Which of the following would allow a digital signal processing filter to create a sharper filter response? Answer Options A) Higher data rate B) More taps C) Lower Q D) Double-precision math routines Correct … [Next page](https://forum.openhamprep.com/c/extra-questions/9.md?page=1)