Quick way to remember: normally you listen to repeater output. Listening to the input of a repeater is the reverse of normal!

Long Explanation

UHF/VHF repeaters receive on one frequency (input frequency) and then re-transmit on another frequency (output frequency), usually with this "split" in input/output (also called RX/TX) frequencies being 600kHz apart (for 2m) either + or -. This is called operating Duplex (vs Simplex where only one frequency is used for both TX and RX). Radios must be configured properly for duplex communication to use a repeater.

"Reverse Split" means operating duplex on a reverse frequency split compared to what is considered "normal" for the situation. (Source) In other words, the usual RX and TX frequencies are swapped (reversed).

Normally everyone using a repeater transmits on the repeater's input (RX) frequency, and receives on the repeater's output (TX) frequency, so when configured correctly your radio will only be listening to the repeater's output (TX) frequency and not listening to other radios' transmissions directly since they will be transmitting on the repeater's input (RX) frequency.

But what if you do want to listen to their transmissions directly? In this case you'll want to listen on the repeater's input (RX) frequency like the repeater does. This might help you determine if a signal is strong enough for both of you to switch to a simplex frequency without using the repeater, or tell you if you can receive a weak signal from where you are even if the repeater can't because it's too far away.

Another situation is if you think someone will be trying to call you on a repeater that you know is broken, powered down, or otherwise not operating, you may wish to reverse the transmit/receive frequencies on your radio so that you are now receiving and transmitting on the frequencies the repeater would if it were working. This would allow you to hear someone who is trying to transmit to a repeater, as well as allowing you to respond on the frequency they will most likely be listening to (the repeater output frequency).

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CTCSS - Continuous Tone Coded Squelch System

Originally invented by Motorola and called Private Line (PL), the repeater access tones 'open' the squelch of the receiver. This allows different users to share a repeater without hearing other conversations, as the other tones will not 'open' their receiver. This technique is also known as subaudible and privacy codes/tones.

The use of CTCSS tones also prevents people from accidentally using a repeater unless they've properly programmed their radio specifically for a particular repeater. Yes, it makes the programming a little more complex, but it also ensures that repeaters remain as quiet as possible, since common radio noise and interference can't activate the repeater (remember, the repeater won't activate unless that CTCSS tone is present). This makes life much easier for all who might be monitoring a repeater, since it will remain quiet unless a human really does want to use it.

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A linked repeater network is a general term for a network of repeaters where signals received by one repeater are repeated by all the repeaters in the network.

Digital repeaters in particular are often linked together in a network, though they may not always repeat all signals received by one repeater because they tend to be smart enough to do so only as needed. But they are capable of repeating all signals as required such that to the user it will appear as though this is what's happening.

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Many repeaters experience problems with picking up RF "noise" from nearby powerlines, buildings, other transmitters, etc. In order to avoid having the repeater retransmit this noise, various methods are used to be certain that only intentional and/or authorized signals are retransmitted.

1. The first method is to have the repeater only open its squelch and retransmit a signal that begins with a tone burst. This is also called Selective Calling, and is much more common in Europe than it is in America. SelCall tone bursts usually consist of 5 in-band DTMF audio tones at the beginning of the transmission.
2. The second method is to have the repeater use DCS (Digital Code Squelch). With DCS enabled the repeater will only open up if the signal contains specific DCS tone sequence, which most modern radios can be configured to output.
3. The third, and probably most common, method is to use a CTCSS (Continuous Tone-Coded Squelch System) subaudible tone; if the tone is not present, the repeater will not retransmit the signal.

If any of these features are in use on the repeater and you do not have your radio correctly configured, the repeater will simply ignore you.

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If transmissions are breaking up on voice peaks then of the given options it is most likely that you are talking too loudly. The key thing to notice here is that the question says it only happens on voice peaks and not all the time, so it is probably not overall transmit power. The other options are associated with other problems.

(Your mouth could also be too close to the microphone, but that's not one of the options given.)

High audio levels can overload one or more stages of the transmitter and result in distortion such as Clipping or Gain Compression. Only the time periods where the overload occurs are affected which would correspond to the voice peaks of the transmission.

If a receiver were overloaded by excessive received power, it would most likely affect the whole signal and not just the voice peaks.

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Memory aid: DT = Dual Tone.

The four acronyms presented are:

• Dual Tone Multi Frequency
• Continuous Tone-Coded Squelch System
• General Packet Radio System
• Digital Smart Technologies for Amateur Radio

Of the four acronyms, Two do not have "Tone" (GPRS and D-STAR) and can be thrown out (and GPRS doesn't even have a "T").

Continuous Tone-Coded Squelch System is a system that adds a Single, Continuous, low frequency tone to your audio system for the entirety of your transmission in order to signal to a receiver to "Break Squelch" and listen.

Dual Tone Multi Frequency uses a pair of tones to signal to another receiver that a keypad button (1-9, A-D, # and *) has been pressed.

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Memory aid: 'group' is in both question and correct answer

A number of different digital radio standards exist such as DMR, D-Star, and Fusion. They usually implement something called a "talk group" which is described by the DMR-MARC FAQ as follows:

Q. What are Talk Groups?

A. Talk Groups are like different work groups that you communicate with. They are programmed as “channels”. Several can share a Time Slot on a repeater like multiple PL codes can share a community repeater. Each talk group can be isolated from the other, but may get a busy tone if the same time slot is in use by another. Greater efficiency can be achieved by bridge routing and trunking techniques. Each radio can have more than one talk group and may scan or roam based on talk group.

Once a radio has been configured to operate with a particular digital repeater, joining a talk group is just a matter of programing your radio with the group's ID or code so you can tell it to listen to or transmit to that group.

Digital repeaters can be operated stand-alone but often they are linked to other repeaters using the same standard in a network. See the bottom of this DMR-MARC FAQ for a list of networks, of which DMR-MARC is one.

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No amateur radio operator has an absolute right to any amateur frequency. When you sign your license application, you're reminded of that and agree to it.

The Strongest or weakest signal or length of time on a frequency does not give you a greater claim to that frequency.

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Simplex channels exist in the UHF/VHF band plans so that stations within mutual communications range can communicate without tying up a repeater. That is the best option of those given.

Really they exist for any purpose where you want to communicate without using a repeater, such as when one isn't available, and will use the same frequency for both receiving and transmitting (known as simplex).

They have nothing to do with repeaters or accessing repeaters.

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Hams use all sorts of Q codes to convey quick messages. QRM means interference from other stations, QTH means location, QSO means 'a conversation', QSY means changing frequency or channel, etc.

In practical use, if you hear another ham say "I'm hearing a little QRM on your signal", it means there's interference from other station transmissions. They might also say "I hear some Q-R-Mary", which means the same thing.

The "M" in QRM means man-made interference, as opposed to the "N" in QRN, which means natural, or atmospheric, interference.

Q - Radio Messy

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This is one of the most commonly used Q Codes. QSY means to change frequency. For example:

"Please QSY to 147.34."
"Copy that, this is KD7BBC, QSY to 147.34"

Or

"Shall we QSY to 146.52 simplex?"

Here is a memory aid:

If you got Q uea SY about a frequency, you would change to a different one.

Or, (S)ee (Y)ou at a different frequency.

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Memory aid: 'Color code' is in both the question and the correct answer

Color code is a similar concept to "CTCSS" or "PL" tones. Your radio must have the correct Color Code in order to open the squelch of the repeater.

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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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