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Subelement T4
Amateur radio practices and station set up
Section T4A
Station setup; microphone, speaker, headphones, filters, power source, connecting a computer, RF grounding
Which of the following is true concerning the microphone connectors on amateur transceivers?
  • All transceivers use the same microphone connector type
  • Correct Answer
    Some connectors include push-to-talk and voltages for powering the microphone
  • All transceivers using the same connector type are wired identically
  • Un-keyed connectors allow any microphone to be connected

With this question you may need to identify the incorrect answers in order to identify the correct one. Watch out for "ALL" in statements since it is uncommon for all radios to work the same. For this question:

TRUE - The correct answer is that "Some" microphone connectors have a push-to-talk button and voltages for powering the microphone. Some modern microphones are quite sophisticated with keypads, back-lighting and more.

FALSE - **All **transceivers DO NOT use the same connector on their microphones, you generally have to have a specific microphone for each model or brand of radio.

FALSE - **All **transceivers using the same connector type ARE NOT neccessarily wired identically.

FALSE - This statement is false: "Un-keyed connectors allow any microphone to be connected."

Last edited by pyrotecman. Register to edit

Tags: electronics radio operation

What could be used in place of a regular speaker to help you copy signals in a noisy area?
  • A video display
  • A low pass filter
  • Correct Answer
    A set of headphones
  • A boom microphone

Noise in your environment can make it hard to hear your radio. You may be operating your radio on a parade route for an event you are working and a marching band is passing by while a message is coming in for you. Headphones are the answer to block out this extraneious noise and better hear the radio.

The keywords here are that "regular speaker" and "headphones" along with "copy" in a "noisy area". Copy means that you are writing down or understanding the transmission, thus you have to be able to hear and what you hear is from the speaker.

Last edited by aj9r. Register to edit

Tags: radio operation

Which is a good reason to use a regulated power supply for communications equipment?
  • Correct Answer
    It prevents voltage fluctuations from reaching sensitive circuits
  • A regulated power supply has FCC approval
  • A fuse or circuit breaker regulates the power
  • Power consumption is independent of load

Here are some facts to help you get this technical question right.

A regulated power supply regulates the output voltage so that it remains at a constant voltage regardless of nominal voltage changes in the mains AC power or when the load increased as you transmit. Radios do have sensitive circuits as well since they have to receive very weak radio signal or small audio signals from the microphone.

A regulated power supply will also prevent "hum" from the AC mains that is a rather common issue with un-regulated power supplies.

The detractor questions could use some comments to let you know why they are incorrect.

Detractor: A fuse or circuit breaker will open when an overload occurs and does not regulate power.

Detractor: Power supplies do not have to have FCC approval. You may desire a U.L. or other safety approval rating.

Detractor: Power consumption is very much dependant upon the load. If the load current increased the power will increase.

Last edited by bdengle32@yahoo.com. Register to edit

Tags: electronics dc power radio components

Where must a filter be installed to reduce harmonic emissions?
  • Correct Answer
    Between the transmitter and the antenna
  • Between the receiver and the transmitter
  • At the station power supply
  • At the microphone

By process of elimination and then confirmation:

A CW (Morse-code) transmitter does not necessarily even have a microphone, so "At the microphone" can be eliminated.

"Emissions" implies OUTPUT from a transmitter, and since transmitter outputs are NEVER (except accidentally) connected to receivers or power supplies, "Between the receiver and the transmitter" and "At the station power supply" can be eliminated.

This leaves "Between the transmitter and the antenna", but to further confirm this choice, transmitter outputs ARE connected to antennas. Transmitters are not normally modified, so the filter is "probably" connected to the transmitter output. Once an emission leaves an antenna, it is no longer subject to filtering (at least not at the transmitting end), so the filter MUST be connected BEFORE the antenna.

Therefore it must be BETWEEN the transmitter and the antenna.

Last edited by hly8j. Register to edit

Tags: antenna filters troubleshooting noise and interference

What type of filter should be connected to a TV receiver as the first step in trying to prevent RF overload from a nearby 2 meter transmitter?
  • Low-pass filter
  • High-pass filter
  • Band-pass filter
  • Correct Answer
    Band-reject filter

Televisions use radio waves to convey both picture and sound to your TV set. Most television stations have gone to digital modulation schemes at UHF frequencies but there are still a few community and low-power stations that use the traditional VHF system. When we transmit on the VHF or 2 meter HAM band our frequencies are close to these TV stations and could cause interference with them.

The filter we need to connect to a TV that is receiving a signal from a nearby 2 meter transmitter needs to block or filter out the 2 meter band. This type of filter is a Band-reject filter. It lets the TV signal through and other signals but rejects the offending signal.

A low pass filter allows frequencies lower than a selected frequency to pass through and will not help in the 2 meter to TV case.

A band pass filter might seem like it should work to just pass the TV band but they do not reject out of band signals that are close (such as 2 meters).

A high pass filter allows frequencies higher than a selected frequency to pass through and will not help in the 2 meter to TV case.

Last edited by bdengle32@yahoo.com. Register to edit

Tags: filters troubleshooting noise and interference

Which of the following would be connected between a transceiver and computer in a packet radio station?
  • Transmatch
  • Mixer
  • Correct Answer
    Terminal node controller
  • Antenna

HAM radio can transmit data as well as our voice conversations. Your computer can be connected to your radio that normally only transmits your voice through a device that converts the digital data into an audio signal that can be transmitted over the radio and receive the signal received by the radio and converts it back to a digital data stream for the computer. This original text messaging system is called packet radio because each text message is sent as a "packet" of data from one radio to one or more receiving radios.

The device that interfaces the computer to the radio is called a "Terminal node controller". Before we all had computers the device that was used to enter and send a user's text was called a terminal, thus the name of this device.

Last edited by dick1952. Register to edit

Tags: digital modes radio operation

How is the computer's sound card used when conducting digital communications using a computer?
  • 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 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

Which type of conductor is best to use for RF grounding?
  • 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

Which would you use to reduce RF current flowing on the shield of an audio 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.

Last edited by jamesmcbride. Register to edit

Tags: radio waves filters troubleshooting noise and interference

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

Where should a mobile transceiver's power negative connection be made?
  • 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.

Last edited by fireglow. Register to edit

Tags: dc power batteries grounding

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