This question does not yet have an explanation! Register to add one

Tags: none

This question does not yet have an explanation! Register to add one

Tags: none

Correct answer: key-down changes the station to transmit, key-up to receive

Break-in keying allows a CW station to automatically switch between transmitting and receiving as the Morse key is operated.

When the key is pressed (key-down), the transmitter is activated.
When the key is released (key-up), the station immediately returns to receive mode.

This allows the operator to hear incoming signals between transmitted characters or words.

• It is not related to theft or unauthorised entry.
• It is not specifically for emergency operation.
• It does not refer to erratic keying by another station.

Therefore, break-in keying means key-down transmits and key-up receives.

Last edited by jim.carroll. Register to edit

Tags: none

Correct answer: listens on a frequency 600 kHz higher than its designated frequency

A repeater’s designated frequency normally refers to its output (transmit) frequency.

With a positive \(600\ \mathrm{kHz}\) split, the repeater’s input frequency is:

\[ f_{\text{input}} = f_{\text{output}} + 600\ \mathrm{kHz} \]

This means it listens on a frequency \(600\ \mathrm{kHz}\) higher than the frequency on which it transmits.

• Transmitting \(600\ \mathrm{kHz}\) higher would describe the opposite shift.
• A repeater does not transmit on two frequencies simultaneously.
• The split is unrelated to modulation type or bandwidth.

Therefore, a repeater with a positive \(600\ \mathrm{kHz}\) split listens on a frequency 600 kHz higher than its designated frequency.

Last edited by jim.carroll. Register to edit

Tags: none

Correct answer: plus 600 kHz above 147 MHz, minus 600 kHz on or below 147 MHz

Repeaters must transmit and receive on different frequencies so they can operate simultaneously without the transmitter overloading the receiver.

The frequency separation (offset) must be:

• large enough to allow practical duplexer filtering between transmit and receive paths
• small enough to keep both frequencies within the 2 m amateur band

In New Zealand, a standard offset of \(600\ \mathrm{kHz}\) has been adopted by band planning authorities to balance these requirements.

The change in shift direction at \(147\ \mathrm{MHz}\) is a coordination measure to prevent repeater input frequencies from overlapping other repeater output frequencies within the band.

• Reversing the direction of the \(600\ \mathrm{kHz}\) offset would cause repeater input/output frequency conflicts within the band plan.
• A \(5\ \mathrm{MHz}\) offset is used on other amateur bands (such as 70 cm), not on 2 metres.

Therefore, the standard 2 metre repeater split in New Zealand is \(\pm 600\ \mathrm{kHz}\) with the changeover at 147 MHz.

Last edited by jim.carroll. Register to edit

Tags: none

Correct answer: 5 MHz

On the 70 cm amateur band (around \(430\text{–}440\ \mathrm{MHz}\) in New Zealand), repeaters use a standard frequency split of \(\pm 5\ \mathrm{MHz}\) between the transmit and receive frequencies. This separation provides sufficient isolation to prevent the repeater transmitter from desensitising its own receiver and allows practical filtering.

• 600 kHz is the standard repeater split used on the 2 metre band, not on 70 cm.
• 1 MHz is not a standard repeater offset in New Zealand.
• 2 MHz is also not a standard allocation for 70 cm repeater operation.

Therefore, the standard frequency offset for 70 cm repeaters in New Zealand is ±5 MHz.

Last edited by jim.carroll. Register to edit

Tags: none

Correct answer: minimum reflected power

An SWR bridge measures how much power is reflected back from the antenna due to impedance mismatch.

When adjusting an antenna matching unit, the goal is to match the antenna impedance to the transmission line so that:

• as much power as possible is delivered to the antenna
• as little power as possible is reflected back toward the transmitter

This corresponds to the lowest SWR and minimum reflected power.

• Maximum reflected power indicates poor matching.
• Equal reflected and transmitted power indicates a severe mismatch.
• Minimum transmitted power would result in poor radiation.

Therefore, you should adjust for minimum reflected power.

Last edited by jim.carroll. Register to edit

Tags: none

This question does not yet have an explanation! Register to add one

Tags: none

This question does not yet have an explanation! Register to add one

Tags: none

Correct answer: a series of nationwide amateur radio linked repeaters in the 70 cm band

In New Zealand, the National System refers to a network of linked amateur radio repeaters, primarily operating on the 70 cm band. These repeaters are interconnected so that a transmission into one repeater can be heard across much of the country.

The system is used for:

• routine long-distance amateur communication

• coordinating nationwide activities and events

• providing wide-area coverage when local repeaters are insufficient

• the legal licensing standard of Amateur operation in New Zealand refers to regulatory documents and certificates, not the repeater network.

• the official New Zealand repeater band plan defines frequency usage and coordination, not a specific linked repeater system.

• a nationwide emergency communications procedure may make use of the National System, but the system itself is the repeater network, not the procedure.

Therefore, the National System is a series of nationwide amateur radio linked repeaters in the 70 cm band.

Last edited by jim.carroll. Register to edit

Tags: none

Correct answer: ignition noise

A noise blanker is designed to suppress short-duration, high-amplitude impulse noise. It detects sharp noise spikes and momentarily mutes the receiver so the impulse does not reach the audio output.

Typical sources of this type of noise include vehicle ignition systems, electric motors, and switching devices, which generate brief repetitive pulses.

• 50 Hz power supply hum is a continuous low-frequency signal and is not impulsive, so a noise blanker is ineffective.
• noise originating from the mixer stage is internal receiver noise and cannot be removed by blanking the incoming signal.
• noise originating from the RF stage is also internal and broadband, not short impulse noise.

Therefore, a noise blanker is most effective at reducing ignition noise.

Last edited by jim.carroll. Register to edit

Tags: none

This question does not yet have an explanation! Register to add one

Tags: none

This question does not yet have an explanation! Register to add one

Tags: none

This question does not yet have an explanation! Register to add one

Tags: none

RIT - "Receiver Incremental Tuning". A transceiver is usually a receiver and transmitter combination sharing a lot of common circuits - such as the various oscillators that determine its operating frequency. RIT provides a tuning facility so the receiver can be separately tuned for a few kHz each side of the transmit frequency, hence giving independent control over the receive frequency.

Last edited by cmscouler. Register to edit

Tags: none

This question does not yet have an explanation! Register to add one

Tags: none

ALC - "Automatic Level Control". Just as we had AGC in a receiver, this is a similar thing for transmitters, usually for the linear amplifiers used in SSB transmitters. Its purpose is to prevent over-driving the linear amplifier stages especially the final amplifier. It may also permit the peaks of an SSB signal to be limited in amplitude to enable an increase in the mean output power of the transmitter to improve the relative signal level at a distant receiver. This function can also involve processing the audio in the transmitter, known as "compression" .

Last edited by cmscouler. Register to edit

Tags: none

This question does not yet have an explanation! Register to add one

Tags: none

This question does not yet have an explanation! Register to add one

Tags: none

This question does not yet have an explanation! Register to add one

Tags: none