Subaudible Tone (CTCSS) Features
Subaudible tones, also known as CTCSS (Continuous Tone-Coded Squelch System) are low-frequency tones that are mixed with a transmission. They are used by many repeaters to limit interfer- ence from other nearby radio transmitters. When a repeater uses a subaudible tone, it does not react to any transmission that does not include that tone.
Your HTX-242 includes all 38 standard subaudible tones. You can set your HTX-242 to include any of these tones with your trans- missions. You can also set your HTX-242 to limit reception to only those transmissions that include the selected tone.
Repeater Operation
Operation through a repeater, where you transmit on one fre- quency and receive on another, is called duplex operation. Opera- tion direct to another station where you transmit and receive on the same frequency is called simplex operation.
A repeater is a station that receives signals on one frequency (the input frequency) and then retransmits them on a different fre- quency (the output frequency). Repeater antennas are typically at the tops of tall buildings or on antenna towers, so a relatively low- power signal can reach the repeater. The repeater retransmits the signal at a higher power. This gives users of low-power transceivers the ability to communicate over a much greater range.
To use a repeater, you must know the repeater’s input and output frequencies. Repeaters are usually identified by their output fre- quency. Thus, a repeater that has an output frequency of 146.94 is referred to as the 146.94 repeater. To determine the input fre- quency you must know the frequency offset (600 kHz for most of the 2-meter band) and the offset direction (+ if you add 600 kHz to the output, or – if you subtract 600 kHz from the output).
Your HTX-242 is programmed with the default 600 kHz frequency offset and direction for the 2-meter band. See “Frequency Offset Defaults” on Page 25. When you tune to a frequency that is nor- mally assigned for repeater use, the HTX-242 automatically selects the correct input frequency if you turned on the AS option.
Memory Channels
Your HTX-242 has 41 memory channels (40 standard memory channels and one calling-frequency memory channel). Each mem- ory channel can hold a transmit and receive frequency, subaudible transmit and receive tones, the transmit power level, and whether subaudible tone transmit and squelch are on or off. The HTX-242 can even scan a selected range and automatically store active fre- quencies in unused memory locations.
