A product detector is a type of mixer used to demodulate AM-family signals, of which CW and SSB are examples. Phase-modulation is more closely related to FM, so both of those answers are incorrect, and combining speech and RF is part of transmission, but this circuit is used in reception.

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Tags: morse code ssb radio components

The Superheterodyne receiver was a great advancement* in radio receivers. Superheterodyne receivers have a very selective set of filters that only pass a fixed intermediate frequency (with a specific bandwidth). The incoming frequency signal is mixed with a second frequency from a local variable frequency oscillator (VFO) with the resulting mixed or heterodyned signal equal to that of the intermediate frequency (IF).

*Prior to this, the tuning of the receiver was done by having the filtering done at the receive frequency via a tuning control. The tuner had to have several stages of tuning elements that precisely tracked one another. The tuning control was a big complex mechanical component subject to trouble. With the superheterodyne receiver it is very simple to adjust the frequency of the VFO with a simple control and the complex tuning of the IF is done once when the receiver is manufactured.

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Tags: radio components

This question wants to know what electrical circuit converts a lower frequency Single-Side-Band (SSB) frequency to a higher frequency. This is done by a Transverter. The other choices will not convert one frequency to another.

• A high-pass filter will reduce a signal's amplitude if it is not higher than the corner frequency of the filter.
• A low-pass filter will reduce a signal's amplitude if it is not lower than the corner frequency of the filter.
• A phase converter will alter the phase of a signal but the frequency will stay the same.

More information can be found here: Transverter

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Tags: radio components

A Modulator is the circuit that "modulates" or encodes the RF carrier frequency with the speech signal in a transmitter. The keyword "combines" indicates that the voice and carrier are put together, which should help you envision a circuit that modulates the signal.

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Tags: radio components

Weak-signal communication involves radio signals whose strength levels are close to or even partially embedded in natural noise. This is a tricky thing, and it generally can't be done with a normal FM transceiver. Different types of antennas could be used, but most importantly a multi-mode transceiver is needed so that modes with lower bandwidth and signal requirements can be used.

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Tags: 2 meter 6 meter vhf

This one is probably pretty obvious if you think about it; an RF power amplifier amplifies (or increases) an RF signal from another device.

Note that a voltage regulator (the most common incorrect response to this question) only regulates the voltage, and does not directly affect power. A voltage regulator might be used as part of a power supply to keep the output voltage constant.

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Tags: radio components radio waves transmit power

FM or Frequency Modulation encodes or "modulates" a signal on a carrier wave by varying the frequency of the carrier. A receiver will decode or "demodulate" an FM signal by detecting the frequency variations using a Frequency Discriminator.

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Tags: frequency modulation radio components

Selectivity is the ability of a receiver to discriminate a desired signal from other adjacent signals. If the IF (Intermediate Frequency) circuits do not filter out adjacent signals then they will also be detected and interfere with the desired signal.

As a memory aid: We need very good Selectivity in order to Discriminate the signal properly.

The distractor answers may need some explanation so you know why they are not the correct answer:

• Tuning rate - Rate means speed, how fast the tuner can change frequencies.
• Sensitivity - this is a measure of how well weak signals can be amplified and picked up out of noise.
• Noise floor - this is the noise energy that hides or obscures our signal; if the signal is less than the noise it cannot be seen just like a floor hides what is below it. Or it is the lowest level that can be detected.

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Tags: definitions

A preamplifier is used to amplify a signal before it gets to the receiver; this might be used if the receiver is not sensitive enough, but most commonly a preamplifier is installed as close to the antenna as possible and before the feedline in order to compensate for feedline loss.

Preamplification is only done on a received signal and is "pre" because it occurs before the receiver receives the signal.

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Tags: radio components transmit power