Question 1

In a push-pull modulator, the carrier suppression is accomplished by:

Accepted Answer

Center-tapped transformers in a push-pull modulator create canceling magnetic fields, which effectively suppress the carrier signal.

Question 2

Which is not an advantage of SSB over AM?

Accepted Answer

SSB (Single Side Band) modulation is more complex in design compared to AM (Amplitude Modulation). This complexity arises from the need to filter out one of the sidebands and possibly the carrier, which requires precise and often more sophisticated circuitry.

Question 3

At 100% modulation, an AM signal has a total power of 1200 watts. If it was converted to SSB and the sideband component had the same amplitude as before, the total power would be:

Accepted Answer

In AM, the carrier power is 2/3 of the total power at 100% modulation. The remaining 1/3 is the power of both sidebands. In SSB, only one sideband is transmitted, so the power is half of the sideband power in AM, which is 200 watts.

Question 4

If the carrier and one of the sidebands are completely eliminated, the resulting signal is referred to as:

Accepted Answer

SSBSC (Single Sideband Suppressed Carrier) refers to the modulation technique where one sideband is transmitted and both the carrier and the other sideband are suppressed or eliminated. This is used to reduce bandwidth and power requirements.

Question 5

Which of the following is NOT an advantage that the phase method of generating has over the filter method?

Accepted Answer

The phase method does not require high Q filters, which is an advantage over the filter method. The filter method relies on high-quality (high Q) filters to select the desired sideband, whereas the phase method can generate a single sideband directly without the need for such filters.

Question 6

In a linear integrated circuit balanced modulator such as the LM1496, carrier suppression is accomplished by:

Accepted Answer

Symmetrical differential amplifier stages in a balanced modulator like the LM1496 are responsible for carrier suppression. This is achieved through the balanced (symmetrical) nature of the circuit, which allows the carrier signal to be canceled out while mixing the input signal with the carrier, leaving only the upper and lower sidebands.

Question 7

The type of sideband that involves having the upper sideband contain different information than the lower sideband is referred to as:

Accepted Answer

Independent sideband transmission allows for the upper and lower sidebands to carry different information, unlike other forms of sideband modulation where both sidebands carry the same information.

Question 8

Which of the following is required for SSB transmission?

Accepted Answer

The answer of Which of the following is required for...

Question 9

Which of the following can be used as an SSB demodulator?

Accepted Answer

A mixer can be used as an SSB (Single Side Band) demodulator by mixing the received signal with a locally generated carrier of the same frequency as the original carrier frequency. This process converts the SSB signal back to its original audio or baseband form.

Question 10

SSB transmitters are usually rated in terms of:

Accepted Answer

SSB transmitters are typically rated in terms of peak envelope power (PEP), which is the maximum power level of the signal during its highest amplitude peaks. This measure is important for understanding the transmitter's capability to handle power without distortion or damage.

Question 11

The major disadvantage of the phase method of SSB generation is:

Accepted Answer

The major disadvantage of the phase method of SSB generation is the requirement of a 90-degree phase-shifting network for the intelligence signal, which can be complex and difficult to implement accurately.

Question 12

The output of a balanced modulator in an SSB transmitter being modulated with a voice intelligence signal is:

Accepted Answer

A balanced modulator in an SSB (Single Side Band) transmitter, when modulated with a voice intelligence signal, outputs a Double Sideband Suppressed Carrier (DSB-SC) signal. This is because it suppresses the carrier frequency, leaving only the upper and lower sidebands, which is a step in generating an SSB signal.

Question 13

Which of the following will not work as a balanced modulator?

Accepted Answer

A balanced modulator is designed to suppress the carrier signal and allow only the sidebands to pass through, which is essential in generating a double sideband suppressed carrier (DSB-SC) signal. A push-pull modulator (A), a ring-diode modulator (B), and an LM1496 integrated circuit stage (C) are all capable of functioning as balanced modulators, effectively suppressing the carrier while allowing the sidebands to pass. However, a dual-gate FET with a band-pass filter (D) does not inherently perform carrier suppression to the extent required for a balanced modulator. The band-pass filter may shape the frequency response but does not contribute to the carrier suppression mechanism necessary for a balanced modulator's operation.

Question 14

The most important advantage of SSB over AM is:

Accepted Answer

SSB is more effective in utilizing the available frequency spectrum because it transmits only one sideband and the carrier, which results in a narrower bandwidth compared to AM.

Question 15

A more recently developed system of sideband that involves compressing the amplitude of the intelligence signal before modulation occurs is called:

Accepted Answer

ACSSB, which stands for Amplitude Compandored Single Sideband, is a method that involves compressing the amplitude of the intelligence signal before modulation occurs, improving signal quality and bandwidth efficiency.

Question 16

The type of sideband that is used for NTSC television video transmission is called:

Accepted Answer

NTSC television video transmission uses vestigial sideband (VSB) modulation. This method is a compromise between single sideband (SSB) and double sideband (DSB) transmission, allowing for more efficient use of bandwidth than DSB and easier receiver design than SSB.

Question 17

The PEP rating of an SSB transmitter is often misleading due to:

Accepted Answer

The PEP (Peak Envelope Power) rating of an SSB (Single Sideband) transmitter can be misleading because it represents the maximum power the transmitter can achieve under specific conditions, which do not necessarily reflect normal operating conditions. Normal voice signals typically only utilize one-third to one-fourth of the PEP rating, and the transmitter's components may not be designed for continuous operation at PEP levels.

Question 18

Crystal filters:

Accepted Answer

The answer of Crystal filters:
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Question 19

In an SSB transmitter having voice modulation using audio frequencies ranging from 100 Hz to 3 kHz, the upper and lower sidebands generated by the balanced modulator are separated by:

Accepted Answer

The answer of In an SSB transmitter having voice modulation...

Question 20

Voice transmission requires an audio frequency range of:

Accepted Answer

The typical frequency range for voice transmission over telephone systems is 100 Hz to 3 kHz. This range is sufficient to understand speech but does not include the full range of human hearing.

Quiz 4: Single-Sideband Communications