Simplex communication refers to the configuration such that only one person can communicate at a time. When a station is transmitting and receiving on the same frequency, the operator can either send or receive, but not both. For amateur radio, simplex communication means that a single frequency is used for both transmitting and receiving.

Transmitting and receiving on the same frequency is the simplest mode of communication, thus the term Simplex.

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Tags: operating procedures radio operation definitions

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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Tags: sub-audible tone radio operation

Pay particular attention on this question. Many people answer this one incorrectly as either CTCSS or Tone Squelch, which are the same thing, or rather, CTCSS squelch and Tone Squelch actually are. They refer to the muting of receiver audio controlled by the presence or absence of a subaudible tone in the signal.

This question is asking specifically about muting of receiver audio (squelch) controlled solely by the presence or absense of an RF signal... meaning any RF signal, not just one with a special tone on it. That is called Carrier squelch, because it squelches the audio whenever a Carrier is not present.

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Tags: radio operation

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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Tags: repeater radio operation sub-audible tone

The amplitude of the modulating signal is converted to frequency variations of the FM (Frequency Modulation) signal. These variations are referred to as carrier deviation or deviation.

A question pool committee member has clarified that PM as used here refers to Phase Modulation

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Tags: frequency modulation

Deviation for FM refers to the amount of frequency variation. As deviation increases, so does the variation of the frequency. An increase in deviation implies that the signal occupies more bandwidth..

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This principle is to "know what you're transmitting." As the control operator, you are responsible to ensure your transmissions meet FCC regulations. If you get a report that your transmissions are causing interference, you are responsible to identify and correct the problem. There are, of course, lots of resources and other operators available to help if the problem remains elusive.

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Tags: harmful interference troubleshooting

Because the radio bands are shared on a cooperative basis, it is important to listen before transmitting to make sure the frequency is available. If the frequency is already in use, simply say 'Excuse me,' give your call sign and change frequencies.

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Tags: harmful interference operating procedures

Phone means voice. The phonetic alphabet is generally understood by operators in all countries, so using it enhances communication in identifying your station.

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Tags: operating procedures call signs

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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Tags: Q signals harmful interference

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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Tags: Q signals operating procedures