Many microphones and radios provide a gain control for the microphone input. If that gain is set too high the audio waveform can exceed the linear range of the microphone preamplifier or the transmitter audio circuitry and the peaks become clipped. Clipping and overdrive produce distorted audio and intermodulation products that make speech harder to understand and can cause splatter into adjacent frequencies. Excessive microphone gain therefore degrades the transmitted audio quality rather than causing frequency instability, a change in SWR, or inversion of the sideband.

Memory aids:

• If the audio sounds harsh, buzzy, or unreadable, reduce the microphone gain — too much gain = clipped/distorted audio.

Last edited by v-man. Register to edit

Tags: none

You enter a transceiver's operating frequency by typing it on the keypad or by tuning with the VFO (tuning) knob. "VFO" stands for Variable Frequency Oscillator; on older radios you often had to change crystals to select frequencies, but most modern radios let you either key the frequency directly on a numeric keypad or adjust it with a tuning/VFO knob.

CTCSS (a subaudible tone often called a PL tone) and DTMF (telephone touch‑tones) are signaling tones used for squelch or control functions and are not used to set the operating frequency. Automatic Frequency Control (AFC) is a receiver feature that helps keep the receiver tuned to an incoming signal, not a means of entering a frequency.

Memory aids:

• VFO = Variable Frequency Oscillator (the tuning knob)
• CTCSS = subaudible "PL" tone (not for setting frequency)
• DTMF = telephone touch‑tones (signaling, not frequency entry)
• AFC = Automatic Frequency Control (keeps the receiver locked to a signal)

Last edited by camplate. Register to edit

Tags: none

Squelch mutes receiver audio when no strong signal is present. It compares the incoming signal level to a threshold and holds the speaker silent until the signal exceeds that threshold. To hear a weak FM signal you must lower the squelch threshold so the receiver audio is not muted for that signal — in other words, set the squelch so the receiver output audio is on all the time (or at least sensitive enough to pass the weak signal).

Turning up the audio volume does not defeat squelch because squelch is applied before the audio amplifier; if the squelch mutes the audio, increasing volume does nothing. Features named "anti-squelch" or "squelch enhancement" are not how you make the receiver pass weaker signals — the correct approach is to lower the squelch threshold.

Memory aids:

• Squelch = silence until the signal is strong enough; lower the threshold to hear weak signals.
• If you hear only static all the time, squelch is set too low; if you hear nothing, squelch may be set too high.

Last edited by amazon10x. Register to edit

Tags: none

If an FM signal is received slightly off frequency, the receiver does not correctly recover the full frequency deviations that carry the audio. Instead of producing a steady change in pitch (as happens with AM or single-sideband when you’re off frequency), the recovered audio becomes distorted or unclear — you’ll hear evidence of missing or altered parts of the modulation rather than a simple pitch shift. In practice this is why manually tuning an FM receiver toward the exact carrier frequency makes the audio progressively clearer; the closer you are to the correct frequency, the more accurately the discriminator reproduces the original audio.

Memory aids:

• FM off-frequency → distortion or loss of clarity
• AM/SSB off-frequency → change in pitch (contrast to FM)
• Mnemonic: “FM needs the right Frequency — otherwise it’s Fouled-up Modulation.”

Last edited by kd7bbc. Register to edit

Tags: none

Scanning on an FM transceiver automatically tunes through a range of frequencies to check for activity. The radio will rapidly switch receive frequencies, pausing on each frequency for a short time to detect a carrier signal that indicates someone is transmitting. If no carrier is detected it moves on to the next frequency.

When a carrier is present the radio’s behavior is usually user-configurable: it can stop on that frequency until manually continued, pause for a few seconds, or remain while the carrier is present and then continue. More advanced scanners can scan a programmed list of specific frequencies (such as repeaters) instead of stepping through a continuous range. This feature is useful for finding other operators or monitoring multiple frequencies when you don’t know exactly which one is active.

• (No memory aids provided.)

Last edited by rjstone. Register to edit

Tags: none

Receiver Incremental Tuning (RIT), also called the Clarifier, is a fine‑tuning control that adjusts only the receiver frequency without changing the transmitter frequency. On single‑sideband (SSB) signals the carrier is suppressed, which often makes voices sound "off" in pitch. Using the RIT/Clarifier you can shift the receive frequency slightly to restore the perceived pitch of the voice until it sounds correct. Note that the direction you adjust RIT to correct pitch will be opposite for upper‑sideband (USB) versus lower‑sideband (LSB) signals, and individual voices naturally vary in pitch.

Memory aids:

• RIT = Receiver Incremental Tuning (aka Clarifier)
• SSB suppresses the carrier, which is why voices can sound "Donald Duck" without RIT adjustment
• USB vs LSB require opposite RIT adjustments

Last edited by brianaburk. Register to edit

Tags: none

On DMR, a “code plug” is just all the settings your radio needs to know what to do.

It’s the configuration data that tells the radio:

• Which frequencies to use
• What color codes and time slots go with each
• Which talkgroups belong on which channels
• How things are organized into zones, scan lists, etc.

That whole bundle of settings is the “code plug.”

It’s not a cable, not a software update, and not the audio codec. Those are all hardware or software pieces. The code plug is the programming info you load into the radio so it can actually use DMR repeaters and talkgroups.

Last edited by kd7bbc. Register to edit

Tags: none

Different operating modes occupy different amounts of bandwidth. By selecting a receiver filter whose bandwidth matches the mode you are using, you pass the wanted signal while rejecting noise and signals on nearby frequencies. A narrower filter reduces the noise floor and helps reject adjacent-channel interference, but if the filter is too narrow for a wide-mode signal you will lose parts of the transmission. Conversely, a wider filter is required for wide FM or other wide modes so the entire signal is heard. Matching filter bandwidth to the mode therefore minimizes noise and interference while preserving the full signal.

Last edited by liaellentron. Register to edit

Tags: none

DMR radios send voice as digital data and include metadata such as the talkgroup (group) identification code with each transmission. To talk to a specific group on a DMR network or repeater you enter that group's identification code (the talkgroup ID); the repeater or network looks at the ID and routes traffic only to radios subscribed to that talkgroup.

CTCSS tones are used for analog squelch, not for selecting digital talkgroups. Storing a frequency in memory only picks the radio frequency and does not select a DMR talkgroup. A code plug can store programmed settings for a radio, but the active talkgroup is selected by entering the talkgroup (identification) code. Automatic identification (your radio ID) identifies the transmitting station but does not choose which group receives the transmission.

Memory aids:

• To select a group, identify it (enter the talkgroup ID).

Last edited by mwhaskew1. Register to edit

Tags: none

Single-sideband (SSB) voice signals contain the information needed for intelligible speech primarily in the lower portion of the audio band — roughly up to a few kilohertz. Telephony and voice communications concentrate on about 300–3000 Hz because that range carries the speech characteristics most important for understanding.

Thermal noise power in a receiver is proportional to its bandwidth, so a narrower receiver filter reduces the amount of noise passing to the detector. However, if the filter is too narrow it will cut off important speech components and reduce intelligibility. A filter around 2400 Hz is narrow enough to reject a significant amount of noise while still passing the essential voice frequencies for understandable SSB speech, giving the best signal-to-noise ratio for SSB reception.

Memory aids:

• SSB voice bandwidth is typically about 2.4–3 kHz
• Narrower filter = less noise, but don’t cut out speech
• Aim for a filter wide enough for intelligibility (around 2400 Hz) yet narrow enough to reduce noise

Last edited by gregor. Register to edit

Tags: none

D-STAR is a digital voice protocol that inserts your call sign into every transmission. Because the call sign is encoded as part of the digital data, you must program your call sign into the transceiver before transmitting; otherwise you would be transmitting without identifying.

Two common sources of confusion:

• D-STAR uses a fixed codec (the radio's vocoder) to convert voice to digital data, so the user does not need to (and generally cannot) select a different codec before transmitting.
• Output power is adjustable on the radio, but there is no requirement to set a particular power value before transmitting — you only need to operate within your license and equipment limits.

Memory aids:

• Remember that D-STAR “tags” transmissions with the operator's call sign automatically, so the call sign must be entered beforehand.

Last edited by kd7bbc. Register to edit

Tags: none