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T2B

OPERATING PROCEDURES

VHF/UHF operating practices: FM repeater, simplex, reverse splits; Access tones: CTCSS, DTMF; DMR operation; Resolving operating problems; Q signals

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T2B011 of 14

What is the purpose of the reverse function on a VHF/UHF transceiver?

Why A repeater listens on its input frequency and retransmits on its output frequency, and your radio normally does the opposite: transmit on the input, receive on the output. Pressing reverse swaps those two, so your receiver tunes to the frequency the other station is actually transmitting on. That lets you hear the distant station's signal directly and judge whether you could work them simplex, or check whether the repeater is even needed.
Watch out Listening on the repeater's output is just normal operation, which is what the radio already does with reverse turned off. The power-related choices describe what a high/low power switch does, not the reverse button.
Reverse = listen where you'd normally talk. If you still hear them in reverse, try simplex.
HamSandwich explanation, first draft. The question and answers are the NCVEC text.
T2B022 of 14

What term describes the use of a sub-audible tone transmitted along with normal voice audio to open the squelch of a receiver?

Why CTCSS stands for Continuous Tone Coded Squelch System, a low frequency tone (roughly 67 to 254 Hz) sent continuously underneath your voice audio. The receiver, usually a repeater, only opens its squelch when it hears the matching tone, which keeps it from being keyed up by noise or by distant stations on the same frequency. The tone is below the normal voice passband, so listeners do not hear it.
Watch out Carrier squelch is the opposite arrangement: any signal strong enough opens the receiver, with no tone required. DTMF is the audible touch-tone keypad signaling used for control functions, not for holding squelch open.
CTCSS = Continuous Tone Coded Squelch System. Continuous and sub-audible; DTMF is the beepy keypad tones you can hear.
HamSandwich explanation, first draft. The question and answers are the NCVEC text.
T2B033 of 14

Which of the following describes a linked repeater network?

Why In a linked repeater network, two or more repeaters are tied together by RF links, microwave, or the internet so that whatever one repeater hears is retransmitted by every repeater in the system. This lets a low-power handheld cover a whole state or region, because your local machine passes the audio to all the others. Statewide emergency nets and wide-area club systems commonly work this way.
Watch out A single repeater with multiple receivers is a voting or satellite-receiver system, which extends coverage on the input side only, not a linked network. APRS is a packet position and message reporting system, not a voice linking method.
Linked = one in, all out. Talk into one repeater, everyone on the network hears you.
HamSandwich explanation, first draft. The question and answers are the NCVEC text.
T2B044 of 14

Which of the following could be the reason you are unable to access a repeater whose output you can hear?

Why Hearing a repeater's output only proves your receiver is on the right frequency; transmitting into it requires three more things to line up. Your transmit offset (usually 600 kHz on 2 meters, 5 MHz on 70 cm) must be the correct size and direction, and if the repeater is tone protected your CTCSS subaudible tone or DCS code must match what the controller expects. Any one of these being wrong lets you hear the machine but never key it up, so all of the listed causes are valid.
Watch out It is tempting to blame only the offset, since that is the most common setup error, but a perfectly correct offset still gets you nowhere if the repeater requires a tone or code you are not sending.
Hearing is receive; accessing is transmit. Check offset, tone, and code before blaming the repeater.
HamSandwich explanation, first draft. The question and answers are the NCVEC text.
T2B055 of 14

Which of the following would cause your FM transmission audio to drop out on voice peaks?

Why FM voice channels are limited to about 5 kHz deviation to fit the receiver's IF passband. Shouting into the mic drives deviation past that limit, so on loud syllables the signal splatters outside the receiver's filter and the audio breaks up or drops out. The cure is to back off from the microphone and speak in a normal, steady voice.
Watch out Too little deviation does the opposite: the recovered audio is weak and quiet all the time, not chopped up only on the loud peaks. Repeater offset errors and high power don't distort voice peaks at all.
Dropouts only on the loud parts = overdeviation. Back off the mic, don't shout.
HamSandwich explanation, first draft. The question and answers are the NCVEC text.
T2B066 of 14

What type of signaling to a repeater uses two simultaneous audio tones?

Why DTMF stands for Dual-Tone Multi-Frequency: each keypad digit sends two audible tones at once, one from a row group and one from a column group, and the repeater's decoder identifies the digit from that unique pair. It is the same touch-tone signaling used by telephones, and hams use it for autopatch, remote control of repeater functions, and linking commands.
Watch out CTCSS is the tempting one, but it sends a single sub-audible tone below 300 Hz that simply unlocks the repeater's receiver, not a pair of audible tones. D-STAR is a digital voice and data mode, and GMRS is a separate licensed radio service entirely.
DTMF = Dual Tone, two tones at once. CTCSS = one quiet Continuous tone.
HamSandwich explanation, first draft. The question and answers are the NCVEC text.
T2B077 of 14

How can you join a digital repeater's "talkgroup"?

Why On DMR and other digital repeater systems, a talkgroup is a logical channel identified by a numeric ID that is carried in the digital data stream. Your radio's codeplug entry for that channel has to contain the correct talkgroup ID (and time slot and color code on DMR) so the network knows which conversation you want to hear and transmit into. Once the ID is programmed, you simply key up; there is no human gatekeeper on the repeater deciding on a per-talkgroup basis.
Watch out Registering is a real step for getting your DMR ID in the first place, but that comes from the radio ID issuing body, not the local Frequency Coordinator or the repeater control operator, and it is separate from selecting a talkgroup. DTMF tones are analog touch-tone signaling used for autopatch and control functions, not for digital talkgroup selection.
Digital = data. Talkgroups are selected by a number in your codeplug, not by a tone or a phone call.
HamSandwich explanation, first draft. The question and answers are the NCVEC text.
T2B088 of 14

Which of the following applies when two stations transmitting on the same frequency interfere with each other?

Why No amateur station or group owns a frequency; FCC rules give no one priority based on being there first (except during emergencies). When two stations find themselves interfering, the expected practice is common courtesy: talk it over and work out who continues, who moves, or how to share. Good amateur practice, which the FCC expects under Part 97, is cooperation rather than claiming rights.
Watch out The choice about the first station having preemptive rights is tempting because it sounds like a traditional priority rule, but frequencies are shared and no station can claim ownership. Requiring both stations to leave is also not the rule, and subaudible tones only control receiver squelch, they do not stop the signals from colliding on the air.
Nobody owns a frequency. When you clash, negotiate, don't claim squatter's rights.
HamSandwich explanation, first draft. The question and answers are the NCVEC text.
T2B099 of 14

Why are simplex channels designated in the VHF/UHF band plans?

Why Simplex means transmitting and receiving on the same frequency with no repeater in the middle. Band plans set aside specific simplex frequencies (146.52 MHz is the national 2 meter FM calling/simplex frequency) so that stations close enough to hear each other directly can just talk, leaving the repeater free for stations that actually need its height and power. Good practice on VHF/UHF FM is to check whether you can work a station simplex and move off the repeater if you can.
Watch out The choice about simple transmitters accessing a repeater without offset is nonsense: a repeater receives on a different frequency than it transmits, so working it without an offset is impossible. Contest and DX operating happen on many frequencies and are not the reason simplex channels exist.
Simplex = radio to radio direct. If you can hear each other without help, get off the repeater. Remember 146.52.
HamSandwich explanation, first draft. The question and answers are the NCVEC text.
T2B1010 of 14

Which Q signal indicates that you are receiving interference from other stations?

Why QRM is the Q signal for interference from other stations, that is, man-made interference from other transmitters. The Q signal set is a shorthand from telegraphy that carried over into voice operating: QRM means "I am being interfered with" by other signals.
Watch out QRN is the close cousin but refers to natural or atmospheric noise such as static crashes from lightning, not other stations. QSB means fading of the signal, and QTH is your location.
QRM = Man-made (other hams). QRN = Nature/Noise. QSB = Signal Bouncing (fading). QTH = The Home spot.
HamSandwich explanation, first draft. The question and answers are the NCVEC text.
T2B1111 of 14

Which Q signal indicates that you are changing frequency?

Why Q signals are three-letter shorthand from CW/traffic practice that carry a fixed meaning. QSY means "I am changing frequency" (or, as a question, "shall I change frequency?"). It is the one you hear when someone moves a contact off a calling frequency to a clear one.
Watch out QSL means "I acknowledge receipt" (and gives us the QSL card), QRZ asks "who is calling me?", and QRU means "I have nothing for you" or "do you have anything for me?"
QSY = "Shift Your frequency." QSL = confirm, QRZ = who's calling, QRU = nothing for you.
HamSandwich explanation, first draft. The question and answers are the NCVEC text.
T2B1212 of 14

What is the digital color code used on DMR repeater systems?

Why DMR repeaters use a Color Code, a number from 0 to 15, that your radio must transmit in order for the repeater to accept the signal. It works much like a CTCSS tone on an analog repeater: it keeps a repeater from being keyed by a co-channel DMR system on the same frequency. The color code must match what the repeater expects, and it is programmed into the radio's channel or codeplug along with frequency, offset, time slot and talkgroup.
Watch out The idea of a code that identifies the CODEC is tempting because DMR does use a vocoder (AMBE+2), but that is fixed by the standard, not signaled by the color code; nothing in DMR auto-programs your offset either.
Color Code = DMR's CTCSS. 16 colors (0-15), match it or the repeater ignores you.
HamSandwich explanation, first draft. The question and answers are the NCVEC text.
T2B1313 of 14

What is the purpose of a squelch function?

Why Squelch is a receiver circuit that keeps the audio output muted until an incoming signal meets a set threshold, usually judged by signal strength or by the absence of noise in the channel. Without it, an idle FM receiver pours out loud white noise (hiss) because the detector amplifies whatever noise is present. Turning the squelch control up raises the threshold so only stronger signals open the audio; turning it down opens the receiver to weaker signals along with more noise.
Watch out Reducing impulse noise is the job of a noise blanker, which works on received signals while they are being heard; squelch simply decides whether you hear anything at all.
Squelch = silence until someone talks. It gates the speaker, it does not clean up the signal.
HamSandwich explanation, first draft. The question and answers are the NCVEC text.
T2B1414 of 14

Which of the following is a "talkgroup"?

Why In DMR (Digital Mobile Radio), every transmission carries a numeric talkgroup ID along with the user's radio ID. Your radio is programmed to unmute only for the talkgroup IDs you have selected, so traffic aimed at other talkgroups passes by silently even though it shares the same repeater and time slot. It works like a digital version of a CTCSS tone, but it identifies a subject or regional network rather than just a repeater.
Watch out The choices about a net with a common interest or an email group describe people gathered around a topic; a DMR talkgroup is the numeric identifier in the data stream that routes and filters the audio, not the humans themselves.
Talkgroup = a number in the DMR data stream, the digital cousin of a CTCSS tone.
HamSandwich explanation, first draft. The question and answers are the NCVEC text.
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