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Subelement T4
Amateur radio practices and station set-up
Section T4A
Station setup: connecting microphones; reducing unwanted emissions; power source; connecting a computer; RF grounding; connecting digital equipment; connecting an SWR meter
What must be considered to determine the minimum current capacity needed for a transceiver's power supply?
  • Efficiency of the transmitter at full power output
  • Receiver and control circuit power
  • Power supply regulation and heat dissipation
  • Correct Answer
    All of these choices are correct

All of these things, efficiency of the load, the load power usage, the regulation method (such as switched vs linear), and the ability to dissipate heat will affect the current capacity needed for a transceiver's power supply. Both the receiver and transmitter are load, and the regulation method of the power supply can be a load as well.

Last edited by rjstone. Register to edit

Tags: arrl chapter 5 arrl module 13

How might a computer be used as part of an amateur radio station?
  • For logging contacts and contact information
  • For sending and/or receiving CW
  • For generating and decoding digital signals
  • Correct Answer
    All of these choices are correct

Computers are used for logging call signs (contacts) and contact information (like band, mode, and frequency).

Computers can send and receive CW (Morse Code). Besides Morse, there are other digital modes that computers can generate and decode, including keyboard-to-keyboard modes like PSK31 and RTTY.

Last edited by k6yxh. Register to edit

Tags: morse code digital modes arrl chapter 5 arrl module 12

Why should wiring between the power source and radio be heavy-gauge wire and kept as short as possible?
  • Correct Answer
    To avoid voltage falling below that needed for proper operation
  • To provide a good counterpoise for the antenna
  • To avoid RF interference
  • All of these choices are correct

Power connections should be:

  • Heavy gauge because heavier gauge wires can conduct more current and have less resistance for a given length.

  • Short as possible because even heavy gauge wire has some resistance, and the longer the wire the more resistance the connection will have.

The more resistance the connection has the more the voltage will drop. So to get the least resistance, and the least voltage drop, you want short heavy gauge wire.

A radio or other electronic device may fail to operate properly or even be damaged if a supply line is so long that the voltage on the other end is below a minimum required level.

Last edited by rjstone. Register to edit

Tags: arrl chapter 5 arrl module 13

Which computer sound card port is connected to a transceiver's headphone or speaker output for operating digital modes?
  • Headphone output
  • Mute
  • Correct Answer
    Microphone or line input
  • PCI or SDI

Even though the question is about digital modes, it is asking about audio connections which are very often used for digital modes on amateur radio even though they are analog connections.

In this case, the question is asking about what port in your computer you should use to interpret the signal you are receiving from your transceiver.

For an amateur using digital modes:

Transceiver Headphones > Computer Line-in/Microphone (as in this question)

Computer Headphones/Speaker > Transceiver Microphone

Remember that headphones and speakers are output devices. Therefore a headphone or speaker output is an output port.

A microphone or line input port is an input port.

Input ports need to be connected to output ports for audio connections to work.

Last edited by chilty. Register to edit

Tags: arrl module 5 arrl module 12

What is the proper location for an external SWR meter?
  • Correct Answer
    In series with the feed line, between the transmitter and antenna
  • In series with the station's ground
  • In parallel with the push-to-talk line and the antenna
  • In series with the power supply cable, as close as possible to the radio

Since the SWR (standing wave ratio) has to do with the quality of the radio frequency signal's match between the impedance of the input to the output, it makes no sense to put it in the station's ground, or push-to-talk line, or in the power supply cable. There might be interesting things to measure in those places, but not with an SWR meter.

Typically, an SWR meter is placed close to the transmitter, so you can tell if the antenna system (antenna and transmission line) is well matched to your transmitter. So it goes in series with the feed line, between the transmitter and antenna.

Last edited by shiv_. Register to edit

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Which of the following connections might be used between a voice transceiver and a computer for digital operation?
  • Receive and transmit mode, status, and location
  • Antenna and RF power
  • Correct Answer
    Receive audio, transmit audio, and push-to-talk (PTT)
  • NMEA GPS location and DC power

Just remember that a large number of digital modes (almost all of the ones used on HF, if not all) can be encoded and decoded by the simple sound card in a reasonably modern computer. For example, RTTY uses AFSK and can easily be decoded from audio by modern computers. Even Slow Scan TV can be encoded and decoded as audio by desktops, laptops, tablets, and smartphones!

Therefore, the only answer here that makes any sense is receive audio, transmit audio, and transmitter keying, the last one so computer software can activate and deactivite the transmitter without the need to do so manually.

Often even a computer's microphone and speaker next to the microphone and speaker of the radio is sufficient to encode and decode digital signals as audio, but obviously this method is more error prone so using audio cables is highly preferable for avoiding errors due to noise in the room.

Last edited by uhammes. Register to edit

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How is a computer's sound card used when conducting digital communications?
  • The sound card communicates between the computer CPU and the video display
  • The sound card records the audio frequency for video display
  • Correct Answer
    The sound card provides audio to the radio's microphone input and converts received audio to digital form
  • All of these choices are correct

"Sound Card Packet" is when your computer basically acts as a TNC (Terminal Node Controller); you connect the audio out of the computer to your radio's microphone input and the receive audio from the radio into the line in port on your computer; The computer then listens to the audio and converts it to digital form and when it needs to transmit the sound card generates the tones that the TNC (similar to a modem) would have produced.

The other choices all involve video display, which is not relevant to sound cards.

Last edited by trippinbilly. Register to edit

Tags: digital modes radio operation arrl chapter 5 arrl module 12

Which of the following conductors provides the lowest impedance to RF signals?
  • Round stranded wire
  • Round copper-clad steel wire
  • Twisted-pair cable
  • Correct Answer
    Flat strap

A good RF ground conductor to go from your radio gear to an Earth ground is a Flat strap if you are talking ground. The width of the flat strap reduces inductance in the conductor and thus is a good ground conductor.

This is a misleading question. It does not mention anything about a ground conductor but just a conductor. Twisted pair conductors do a better job with regard to EMI/RFI as is the case with CAT5/6 cables. So it should be revised to state what the purpose for the cable is.

Last edited by tlhall93. Register to edit

Tags: electronics grounding arrl chapter 9 arrl module 23

Which of the following could you use to cure distorted audio caused by RF current on the shield of a microphone cable?
  • Band-pass filter
  • Low-pass filter
  • Preamplifier
  • Correct Answer
    Ferrite choke

A Ferrite Choke can be placed on a cable to reduce current flow conducted on the shield of audio (and power) cables.

The grey tubes or clamp on ferrite devices add inductance to the cable to block the common mode RF energy that may leak from the radio onto the cables attached to the radio.

Bandpass and low pass filters are too complex to design, test and implement compared to the simplicity of placing a ferrite choke on the cable.

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Tags: radio waves filters troubleshooting noise and interference arrl chapter 9 arrl module 23

What is the source of a high-pitched whine that varies with engine speed in a mobile transceiver's receive audio?
  • The ignition system
  • Correct Answer
    The alternator
  • The electric fuel pump
  • Anti-lock braking system controllers

The alternator in your vehicle is an AC generator that is then rectified to produce the DC voltage to charge the battery and run the vehicle's electrical system. It generates a rather high frequency AC signal that can have audio frequency components that can get into the radio's audio amplifier. Sometimes this is because of a weak battery or the design of the electrical system.

Fortunately you can filter out this whine with a 12 Volt power line filter.

Last edited by kb1fyr. Register to edit

Tags: troubleshooting mobile operation noise and interference arrl chapter 5 arrl module 13

Where should the negative return connection of a mobile transceiver's power cable be connected?
  • Correct Answer
    At the battery or engine block ground strap
  • At the antenna mount
  • To any metal part of the vehicle
  • Through the transceiver's mounting bracket

A mobile transceiver can draw many Amperes of current when transmitting. That current needs to come directly from the battery. Using another electrical path could reduce the current available and hinder the tranceiver's performance.

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