Selective Calling - Baofeng UV-82 User Manual

Figure 1—CTCSS offers an effective solution for repeater systems with overlapping coverage. In this example, the ham
who lives in the overlapping zone can send a 71.9-Hz tone to use the KX4V repeater, or a 100-Hz tone to use the WA4ABC
machine.

Selective Calling

Sometimes you want to be a little "selective" about the signals you receive. You want to be available when friends call, but you
don't want to hear all the other noise and chatter on the frequency. CTCSS provides the solution!
If your rig is equipped with a CTCSS decoder, you can switch it on and hear nothing until someone transmits using the correct
tone. This is handy when you're driving with your family (not everyone appreciates the sounds of Amateur Radio!), or when you're
busy at home.
This technique often works better on simplex than through repeaters. Many repeater systems will not pass CTCSS tones. So, if
you transmit using a CTCSS tone on the repeater input, it may not be present on the output. The easiest way to find out is to set up
a test with a friend.
Be careful when using CTCSS for selective calling. Most amateur transceivers don't offer an easy way to disable the CTCSS
decoder. Some H-Ts include a "monitor" button that opens the squelch even when the decoder is on, but most mobiles do not. Just
because your radio is silent, that doesn't mean that the frequency isn't in use. Disable your decoder and check the frequency before
you transmit.
CTCSS can also be used for a type of selective paging. For example, some hams live in areas where it is possible to hear more
than two repeaters on the same frequency (although they can usually access only the local machine). To eliminate this irritating
problem, the repeater trustee can set up the system to transmit a continuous CTCSS tone on the output frequency (see Figure 2).
Everyone who owns a rig equipped with a CTCSS decoder can set their decoder to accept signals carrying that tone only. This
automatically screens out transmissions from the distant machine—only the local repeater is heard!