TO: ALL WOOD COUNTY EMERGENCY COMMUNICATIONS AMATEURS
ALL NON-WOOD COUNTY EMERGENCY COMMUNICATIONS AMATERUS
FROM: KEN HARRIS WA8LLM
WOOD COUNTY EMERGENCY COMMUNICATIONS INCORPORATED
WOOD COUNTY BULLETIN NR 12.08 DATE: February 19, 2012
SUBJECT: WHAT IS CTCSS?
CTCSS are the letters that stand for Continuous Tone Coded Squelch System. Different radio manufactures give CTCSS different names. Motorola calls their system "PL" or "Private Line". General Electric calls their system "CG" or "Channel Guard” RCA calls their system "QC" or "Quiet Channel". Kenwood calls their system "QT" or "Quiet Tone". And, a lot of Amateurs who use CTCSS just call it "Tone"
CTCSS employs sub-audible tones, which are below the normal 300 Hz to 3000 Hz voice range of the radio. This a low level, low frequency tone which is transmitted on the radio frequency carrier at the same time as the voice signal. The frequency range of the CTCSS is between 67.0 Hz, and 254.1 Hz. The frequency of the CTCSS is so low that it's almost out of the hearing range.
The transmitted CTCSS tone is used to tell the receivers on the same Radio Frequency, with the same tone, to turn on the radio's speaker so the audio of the transmitting station can be heard. The CTCSS tone does not keep anyone from hearing the transmitting station’s audio, it just keeps the receiving station from hearing other systems, on the same frequency, without the proper tone, or no tone at all, from being heard.
CTCSS is used to keep other stations that are not a part of a radio system or network, on the same radio frequency from being heard. It does not keep other transmitters from covering up a station that you want to hear. CTCSS does not keep other people on the same frequency from hearing your transmissions. So, it's not a way to send secret messages.
If more than one system is sharing the same radio frequency, or channel, the CTCSS should be disabled long enough to monitor the frequency and make sure someone else isn't using the channel. Some radios are equipped to disable the CTCSS when the microphone is lifted off the microphone hanger. Some radios have a "Monitor Button" that can be pressed. In any case two or more radios using different CTCSS tones can not be transmitting at the same time, they are just sharing a radio frequency or channel.
Ken Harris WA8LLM
WCEC
Wood County WV