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Subelement T7
Station equipment; common transmitter and receiver problems, antenna measurements and troubleshooting, basic repair and testing
Section T7B
Common transmitter and receiver problems; symptoms of overload and overdrive, distortion, interference, over and under modulation, RF feedback, off frequency signals; fading and noise; problems with digital communications interfaces
What can you do if you are told your FM handheld or mobile transceiver is over deviating?
  • Talk louder into the microphone
  • Let the transceiver cool off
  • Change to a higher power level
  • Correct Answer
    Talk farther away from the microphone

The louder the voice signal in an FM transmitter the greater the frequency deviation of the modulator. If we are over deviating the frequency then we need to reduce the amplitude of our voice. Therefore the correct answer is to talk farther away from the microphone or not talk so loudly.

Last edited by davsel. Register to edit

Tags: frequency modulation best practices

What is meant by fundamental overload in reference to a receiver?
  • Too much voltage from the power supply
  • Too much current from the power supply
  • Correct Answer
    Interference caused by very strong signals
  • Interference caused by turning the volume up too high

A very strong transmitted signal can be so strong that it overloads the input of the receiver such that normal operation is not possible.

Last edited by tomf. Register to edit

Tags: noise and interference troubleshooting definitions

Which of the following may be a cause of radio frequency interference?
  • Fundamental overload
  • Harmonics
  • Spurious emissions
  • Correct Answer
    All of these choices are correct

There are many things that can cause interference with radio signals. All three of those listed here can cause interference, therefore the correct answer is "All of these choices are correct".

Fundamental overload - This is a case when the transmitted signal is so strong that it overloads the receiver which prevents proper reception of the desired signal.

Harmonics - When a sine wave is distorted (not pure) it creates harmonics that are integer multiples of the fundamental frequency; these harmonics end up getting into receivers at these harmonic frequencies interfering with operation on those frequencies. See this reference: 5.0 Transmitter Harmonic Emissions.

Spurious emissions - There are a number of undesirable emissions that can interfere with normal signal reception. Most of these can be termed Spurious emissions. From ITU, 1.145 "Spurious emissions include harmonic emissions, parasitic emissions, intermodulation products and frequency conversion products but exclude out-of-band emissions."

Last edited by rjstone. Register to edit

Tags: noise and interference

What is the most likely cause of interference to a non-cordless telephone from a nearby transmitter?
  • Harmonics from the transmitter
  • Correct Answer
    The telephone is inadvertently acting as a radio receiver
  • Poor station grounding
  • Improper transmitter adjustment

Sometimes a strong RF signal can get into the circuitry of other devices, such as stereos, telephones and audio amplifiers in public address (PA) systems, and be demodulated such that they inadvertently act as a radio receiver. Take a look at the FCC Notice labels on modern electronic devices in your home to see recommendations on how to reduce interference. Amateur radio operators can reduce emissions that may interfere with a neighbor's electronic devices by installing filters, reorienting antennas or moving to a new location.

Last edited by nyarasha. Register to edit

Tags: harmful interference noise and interference troubleshooting

What is a logical first step when attempting to cure a radio frequency interference problem in a nearby telephone?
  • Install a low-pass filter at the transmitter
  • Install a high-pass filter at the transmitter
  • Correct Answer
    Install an RF filter at the telephone
  • Improve station grounding

Often the best way to elliminate RF interference is to place an RF filter on the cable to the telephone. More information can be found here: RF interference

Last edited by d0sawxkvs98cmewn+sk2gwoxlra=. Register to edit

Tags: troubleshooting noise and interference

What should you do first if someone tells you that your station's transmissions are interfering with their radio or TV reception?
  • Correct Answer
    Make sure that your station is functioning properly and that it does not cause interference to your own television
  • Immediately turn off your transmitter and contact the nearest FCC office for assistance
  • Tell them that your license gives you the right to transmit and nothing can be done to reduce the interference
  • Continue operating normally because your equipment cannot possibly cause any interference

Making sure your station is functioning properly and does not interfere with your electronic devices is always a great starting point. As you look at the distractor answers they each have something that is quite unreasonable so you can discount them.

Last edited by aj9r. Register to edit

Tags: troubleshooting best practices noise and interference

Which of the following may be useful in correcting a radio frequency interference problem?
  • Snap-on ferrite chokes
  • Low-pass and high-pass filters
  • Band-reject and band-pass filters
  • Correct Answer
    All of these choices are correct

Sometimes it may take more than one action or filter type to prevent interference. Each of these techniques are appropriate choices such that the correct answer is "All of the choices are correct". If you cannot solve the interference problem yourself, ask a fellow ham to help assist you in finding a solution.

Last edited by ikxt5. Register to edit

Tags: troubleshooting noise and interference

What should you do if a "Part 15" device in your neighbor's home is causing harmful interference to your amateur station?
  • Work with your neighbor to identify the offending device
  • Politely inform your neighbor about the rules that require him to stop using the device if it causes interference
  • Check your station and make sure it meets the standards of good amateur practice
  • Correct Answer
    All of these choices are correct

Cooperation with others is the best way to start solving an interference problem. Many devices, especially digital computers and peripherals, generate RF interference. Turning off devices one at a time is a good way to locate an offending device. For more information see: RF interference

Last edited by str8schuter. Register to edit

Tags: troubleshooting noise and interference best practices

What could be happening if another operator reports a variable high-pitched whine on the audio from your mobile transmitter?
  • Your microphone is picking up noise from an open window
  • You have the volume on your receiver set too high
  • You need to adjust your squelch control
  • Correct Answer
    Noise on the vehicle's electrical system is being transmitted along with your speech audio

The key word in the question is "mobile transmitter" which means a transciever in your vehicle. The alternator of your vehicle can generate noise that can tag along with the signal transmitted by your radio. Sometimes the whine varies with the RPM of the engine. The best way to prevent this interference is to put filters on the DC power line going to the transceiver.

Last edited by aust. Register to edit

Tags: troubleshooting noise and interference mobile operation

What might be the problem if you receive a report that your audio signal through the repeater is distorted or unintelligible?
  • Your transmitter may be slightly off frequency
  • Your batteries may be running low
  • You could be in a bad location
  • Correct Answer
    All of these choices are correct

How do each of these cause your signal to be distorted or unintelligible?

"Your transmitter may be slightly off frequency" - If your transmitter is slightly off frequency the receiver will not be able to demodulate the signal and it may sound garbled, distorted and low in volume.

"Your batteries may be running low" - When your batteries are low the audio amplifier cannot generate the proper amplitude signals; the signal is limited by the lower than normal voltage which clips the signal causing it to be distorted.

Also, "You could be in a bad location" - As in real estate, location, location and location are vital. Multipath signals can cause an interference pattern that can make the received audio sound bad.

Last edited by jmv146. Register to edit

Tags: noise and interference batteries troubleshooting radio operation

What is a symptom of RF feedback in a transmitter or transceiver?
  • Excessive SWR at the antenna connection
  • The transmitter will not stay on the desired frequency
  • Correct Answer
    Reports of garbled, distorted, or unintelligible transmissions
  • Frequent blowing of power supply fuses

Your own transmitter output can be picked up by the sensitive circuits inside your microphone. This is called RF feedback. The symptom is that the transmission may be distorted, garbled or unitelligible.

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

Tags: noise and interference radio waves troubleshooting

What does the acronym "BER" mean when applied to digital communications systems?
  • Baud Enhancement Recovery
  • Baud Error Removal
  • Correct Answer
    Bit Error Rate
  • Bit Exponent Resource

BER is the acronym for Bit Error Rate. In digital communication system the data is sent as individual bits of 1 or 0. Errors in the digital bit streams are measured as a Bit error rate (number of errors divided by total number of bits and displayed as a percentage).

The distractors answers are non-sense.

Last edited by aj9r. Register to edit

Tags: digital modes definitions

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