Some microphones have an adjustable gain control. Some radios have an internal gain control to trim the audio gain of the microphone. If the gain is set too high it can exceed the range that circuitry can handle and will cause the audio signal to be distorted. Distortion might be fine for your old tube type guitar amplifier but it will render your signal quality as unreadable.

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Tags: troubleshooting noise and interference

VFO means Variable Frequency Oscillator; back in the time of crystals you often had to "program" a radio by changing crystals in the radio and then using a knob to select them. Modern radios are much easier to set up; most of them you can simply type in the frequency you want on the keypad. Some lack a keypad, but have a "tuning knob", or "VFO knob". Many have both options, since each has its uses.

CTCSS refers to a subaudible tone (also called a PL tone or a privacy code by FRS manufacturers) and DTMF tones are the tones generated when you press a key on your telephone; neither has anything to do with entering the operating frequency. Automatic Frequency Control keeps the receiver tuned to an incoming signal - thus it is not a method of entering an operating frequency.

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Tags: radio operation

The squelch control on a transceiver will "squelch" or mute the noise when no signal is received.

The receiver portion of the transceiver is very sensitive and has variable amplification to give gain to weak signals. When there is no signal to receive, this gain is at maximum which makes the noise received as loud as a normal signal. Fortunately we do not have to listen to that noise because we can adjust the squelch control to mute or turn off signals that are not stronger than the setting we choose.

The squelch circuit watches the signal strength detector's output and turns on the signal when it is strong enough. By turning the squelch control up too high you may miss weaker stations. By turning it too low, you will hear the "white noise" received continuously or intermittently as the background noise varies.

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Tags: radio operation

The ability of most radios to store/program and recall our favorite frequencies gives us quick access to them. These memories can be programmed with more than just the frequency that is needed. For example to reach a repeater we need the correct frequency, input offset frequency and CTCSS tone.

The distractor answers may sound right but remember the key words here are frequency, which is found in the question and correct answer, quick and memory. A good memory is important to get the right frequency recalled quickly.

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Tags: radio operation

Ignition interference is interference that comes from the ignition of a vehicle engine. Newer vehicles seem to have this problem less than older ones did, but it is still not uncommon to have an engine that produces enough noise (particularly if your power or feed lines are poorly shielded) to cause your radio's squelch to open when there is no real signal or even to make it more difficult to hear a weak signal.

A noise blanker is a device that is designed to filter out some of this interference. They work in different ways, and some work better than others.

Note that with ignition interference, changing the frequency (which is what a Receiver Incremental Tuning (RIT) control would do), is not going to help; increasing the squelch setting might help you ignore the problem if the noise is slight, but decreasing it would certainly not help...

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Tags: troubleshooting radio operation noise and interference hf

RIT stands for Receiver Incremental Tuning. It is a fine tuning control to adjust the receiver frequency without adjusting the transmitter frequency.

While SSB is a very efficient transmission mode, everyone ends up sounding somewhat like Donald Duck. This is due to the fact that the transmit carrier frequency is missing. RIT Stands for Receiver Incremental Tuning which in effect, recreates the signal's missing carrier transmit frequency. When the RIT adjustment is misadjusted, the result can be a voice which is too high or too low sounding. Adjust the RIT until the voice sounds correct. Keep in mind some people have naturally higher voices than others. The direction you adjust the RIT will be in opposite directions for upper sideband (USB) vs. lower sideband (LSB), SSB signals.

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Tags: radio operation hf

Sometimes you may have a signal coming in that is slightly distorted due to the transmitting station being slightly off frequency OR because of an issue within your radio where the frequency tolerances are slightly off (radio need a tune up??) OR maybe just atmospheric conditions, etc.... So maybe you are on frequency 14.150 MHz but you are unable to hear the other station clearly. In this case use the Receiver Incremental Tuning (RIT) knob (or buttons) to swing up or down a bit to dial in (tune in) the signal and hear it more clearly. Your transmit signal would remain as 14.150 MHz but your receive might now be tuned to 14.152 MHz (for example).

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Tags: definitions radio operation hf

What is the advantage of having multiple receive bandwidth choices on a multimode transceiver?

Different modes use different amounts of bandwidth; if you are using a narrow receive bandwidth and the mode is wide FM, you will only "hear" a portion of the signal. On the other hand if you're using a wide FM receive bandwidth and the mode is narrow FM, you may not be able to make out the signal at all and there could be interference from other stations on nearby frequencies. The best signal will be experienced when the receiver is expecting the same amount of bandwidth that the transmitter is transmitting.

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Tags: radio operation bandwidth noise and interference hf

SSB is Single Sideband From HamUniverse.com

The information contained in the average human voice needed to understand the voice is contained within about the first 3000hz of the human hearing range. Frequencies of the human voice beyond this range are not needed for communication purposes and are filtered out in the modulation process. So the average bandwidth of a SSB signal is about 3000hz wide with all of the voice characteristics needed within that range to be understandable.

Hearing Frequency Range Starting with the main frequency range, it is the frequency range of human hearing, which is responsible for the perception of speech. It covers the frequencies from 300 to 3000 Hz. The range of frequencies in which the intelligibility and the recognition of the tuning characteristics are concerned is between the above mentioned frequency. This frequency range is used for voice communication in telephony and is the range the human ear is the most sensitive. Because of this, a 2400Hz filter will generally leave enough of the voice characteristics to be understandable but filter out much of the noise. (See also http://www.seaindia.in/blog/human-voice-frequency-range/)

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Tags: filters ssb noise and interference hf

Morse code (or CW, Continuous Wave) communications use far less bandwidth than voice modes; because you only need to be able to definitely discern whether or not the carrier is there (so you can hear the on/off of the morse code) you need very little bandwidth and so your receive filter can be very small. In fact, question T8A11 states that the approximate minimum bandwidth required to transmit a CW signal is 150 Hz.

As a point to remember, any time you see a question regarding CW and bandwidth, CW will pretty much be the smallest number there. More information about CW bandwidth can be found here.

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Tags: noise and interference filters morse code

A repeater is a ham radio station with Automatic Control that listens on one frequency (the receive frequency) and retransmits anything it receives on another frequency (the transmit frequency). The difference (distance) between those two frequencies is commonly referred to as the repeater offset. Commonly used bands have conventions for what this offset should be, and most commonly the offset is specified as simply positive (\(+\)) or negative (\(-\)).

On 2 meters the normal offset is \(600\) kHz (that's another test question). 70 cm uses \(5\) MHz (that's another). So, if you have a 2 meter repeater on \(147.34\) MHz with a positive (\(+\)) offset you will listen to the repeater on its transmit frequency of \(147.34\) MHz and transmit to the repeater on its receive frequency of \(147.94\) MHz (\(147.34\) MHz \(+\) \(600\) KHz).

Similarly, a \(146.62\) repeater with a negative (\(-\)) offset you will listen to the repeater on its transmit frequency of \(146.62\) and transmit to the repeater on its receive frequency of \(146.02\) (\(146.62\) MHz - \(600\) KHz).

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Tags: repeater definitions