Keying the buffer stage in a transmitter helps stabilize the oscillator frequency during keying. This prevents unwanted frequency variations, ensuring that the transmitter stays on the desired frequency.

In a single-sideband transmitter, carrier suppression primarily occurs in the balanced modulator stage, where the carrier is effectively canceled, leaving only the sidebands.

In a Hartley oscillator, positive feedback is established using a special coil with a tap in the middle. Think of it like a water fountain where some of the water flows back into the fountain’s reservoir, helping it keep spraying water continuously. In the oscillator, this feedback is like a loop that keeps the electronic waves going in a circle, creating a steady signal.

Spread spectrum communication refers to a wide-band communications system where the RF carrier varies according to a predetermined sequence. It spreads the signal over a larger bandwidth, making it resistant to interference.

Direct sequence is the term used for a spread spectrum communications system where a very fast binary bit stream is used to shift the phase of an RF carrier.

When tuning a power amplifier for neutralization, the goal is to achieve a minimum change in grid current as the output circuit is adjusted. This indicates that the neutralization is optimized and that unwanted oscillations are minimized.

One advantage of using ASCII over Baudot code is that ASCII includes both upper and lower case text characters, providing more versatility for text communication.

A pseudo-random sequence is used to produce a predetermined alteration in the carrier for spread spectrum communication. It helps in spreading the signal over a wide bandwidth in a controlled manner.

Frequency hopping is used with spread spectrum transmission, as it’s a technique to spread the signal over a wide frequency range.

In AMTOR ARQ (Mode A), the receiving station automatically requests repeats when it detects errors, making it an automatic repeat request (ARQ) error control system.

Neutralization is necessary for some vacuum-tube amplifiers to cancel the oscillation caused by the effects of interelectrode capacitance. This helps prevent parasitic oscillations and ensures stable amplifier operation.

Parasitic oscillations are more likely to occur in RF power output stages due to the high-frequency operation and complex interactions between components in this stage.

APRS (Automatic Packet Reporting System) primarily focuses on functions like two-way messaging, telemetry, and broadcasting amateur-specific local information. It does not inherently support automatic link establishment, as it operates in an unconnected broadcast fashion.

The correct answer, C) a carrier null and multiplying the modulation frequency by the modulation index, is based on the principle that effectively isolates the modulated signal’s frequency deviation for accurate measurement. By nulling the carrier signal, this method minimizes the carrier’s influence, allowing the deviation meter to focus solely on the effects of modulation. Multiplying the modulation frequency by the modulation index then provides a direct calculation of the frequency deviation. This technique ensures that the deviation meter accurately reflects the relationship between the modulation characteristics and the signal’s actual frequency deviation, making it particularly suitable for precise frequency deviation measurements in FM and PM signals.

In FM, the extent to which the carrier frequency deviates from the center frequency is determined only by the amplitude (strength) of the modulating audio signal, not by its frequency.

A single-sideband phone signal can be produced by using a balanced modulator followed by a filter, which removes one of the sidebands and the carrier, leaving only the desired sideband.

Flat-topping occurs when the amplitude of the transmitted signal is pushed beyond the amplifier’s capability to linearly amplify, resulting in the clipping of the signal’s peaks. This condition is most often the result of excessive audio drive or an overly aggressive gain setting in the transmitter’s audio or RF stages.

The Baudot code includes 5 information bits for each character it represents. This limits its character set to 32 different characters.

Intermodulation interference can create unwanted signals at the sum and difference frequencies of the original signals. In this case, if the receiver is tuned to 146.70 MHz and interferes with a transmitter at 146.52 MHz, the other likely interfering frequencies are approximately 146.34 MHz (146.70 MHz – 146.52 MHz) and 146.61 MHz (146.70 MHz + 146.52 MHz).

In a simple 2-stage CW transmitter, the RF transformer serves the dual purpose of inductively coupling the oscillator and amplifier stages while also being part of a tuned circuit, helping to shape and resonate the transmitted signal.

When testing a single-sideband transmitter with a two-tone generator, the peak power output is typically twice the RF power output of any of the individual tones since both tones are independently amplified.

When verifying an FM transmitter’s performance, three critical parameters to check are its power output, frequency deviation, and frequency stability. These factors ensure that the transmitter is operating correctly and within specified limits.

In AMTOR FEC (Mode B), each character is sent twice as a form of error correction, ensuring that the receiver can recover the original data.

To represent 256 discrete levels, you would need 8 bits. Each bit can have two possible values (0 or 1), and with 8 bits, you can represent 2^8 = 256 different combinations.

The question refers to “compression” rather than “clipping.” In this context, RF clipping (compression) is generally considered easier to implement than AF (audio frequency) clipping. RF clipping would result in massive interference to everyone on the bands, much like splatter. RF Compression is easier to do.