What kind of input signal could be used to test the amplitude linearity of a single-sideband transmitter while viewing the output on an oscilloscope?

Get ready for the FCC General Radiotelephone Operator License (GROL) exam. Study with flashcards and multiple choice questions, each with hints and detailed explanations. Prepare effectively for your licensing test!

Multiple Choice

What kind of input signal could be used to test the amplitude linearity of a single-sideband transmitter while viewing the output on an oscilloscope?

To check amplitude linearity in an SSB transmitter, you want a test signal that stresses how the system responds when multiple audio frequencies are present at once. A two-tone audio-frequency sine wave does this perfectly. If the modulator and subsequent stages are perfectly linear, the RF output will reflect the input tones without creating new tones. But real hardware isn’t perfectly linear; nonlinearities mix the two input tones and produce intermodulation products at the sums and differences of those tones (and their harmonics). These extra components show up clearly on an oscilloscope or spectrum analyzer and reveal how well the amplitude is being preserved across a range of inputs. Using a single audio sine wave wouldn’t expose intermodulation effects, because there’s only one frequency to mix with. Whistling in the microphone is an uncontrolled, irregular signal, not a clean test stimulus. A square wave contains many harmonics, which can obscure the specific intermodulation behavior you’re trying to assess and isn’t as effective for evaluating how the transmitter handles small, simultaneous modulating signals.

To check amplitude linearity in an SSB transmitter, you want a test signal that stresses how the system responds when multiple audio frequencies are present at once. A two-tone audio-frequency sine wave does this perfectly. If the modulator and subsequent stages are perfectly linear, the RF output will reflect the input tones without creating new tones. But real hardware isn’t perfectly linear; nonlinearities mix the two input tones and produce intermodulation products at the sums and differences of those tones (and their harmonics). These extra components show up clearly on an oscilloscope or spectrum analyzer and reveal how well the amplitude is being preserved across a range of inputs.

Using a single audio sine wave wouldn’t expose intermodulation effects, because there’s only one frequency to mix with. Whistling in the microphone is an uncontrolled, irregular signal, not a clean test stimulus. A square wave contains many harmonics, which can obscure the specific intermodulation behavior you’re trying to assess and isn’t as effective for evaluating how the transmitter handles small, simultaneous modulating signals.

More practice questions