CTCSS stands for Continuous Tone Coded Squelch System. Basically what it does is this: it adds a tone into your transmission at a certain frequency. Other radios must have the same CTCSS tone or code set to hear the transmission. It will also be heard if the radio has CTCSS and DCS off.
Different CTCSS codes have different frequencies, and this is how it filters out other people - as long as they have a different CTCSS, or no CTCSS, then your radio will not pass any audio to the speaker. A radio with CTCSS enabled will only pass audio for the tone it has set.
DCS works the same, apart from it being digital instead. It stands for Digitally Coded Squelch. It sends a number repeatedly encoded in digital as you speak, in the low frequencies so you do not hear it. If someone else transmits on the channel with a different or no DCS, the radio will not unmute. If they transmit with the same DCS as you, then your radio will unmute. DCS is newer than CTCSS, and has more codes. This gives a lower chance of picking the same code as someone else.
Now that you understand how these work, I also want to clear something up. Some manufacturers call them "Privacy tones" or Privacy codes" or even act like they are different channels, and advertise that the radio has "968 channel combinations." All of this is completely untrue. CTCSS and DCS don't stop anyone from listening to you, they just stop you from hearing other people. If someone has a radio with no CTCSS and DCS on, they will be able to hear everyone on the channel/frequency, including people using CTCSS and DCS.
CTCSS and DCS do not make additional channels. If someone is on the same channel with a different code, then it's not a different channel. If you stand next to them and both transmit, your radios will interfere because they will still be trying to use the same channel at the same time. On PMR446, there are only 8 channels (or 16 channels in new radios after the law was changed to allow 8 new channels), and no CTCSS or DCS can change that. The same with FRS, GMRS or any other radio band.
Please
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THKS FOR THE INFO. I AM NEW TO THIS, BUT ENJOYING LEARNING ABOUT THIS RADIO. I REALLY LIKE THE LINCOLN II+.
ReplyDeleteBrilliant info and very nice knowledge about ctss and cdcss i just came to learn hear before purchasing frequency counter
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ReplyDeleteThanks for the clear explanation. So, if I start scanning on all 8 channels and it picks up a channel that uses CTCSS with a tone or DCS with a code, I will hear it and understand their broadcast?
ReplyDeleteYes that is correct. If you scan all 8 channels and don't have your radio setup with a ctcss or dcs tone you will hear and understand someone broadcasting on the same channel with or without a tone.
DeleteSo the radio A on ch 1 no tone can and will receive a transmitted radio B on ch1 with a tone. But radio B will not hear radio A broadcast.
Thanks for your great clear info where i was long searching for
DeleteHow do you find the right code for a frequency?
ReplyDeleteI like your explanation of the different standards. Thanks.
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DeleteSpeedway New Zealand insist all competitors listen with a receiver on 455.05625 Mhz using CTCSS 123 Hz when competing. This receiver sold by their agent is expensive as a single use unit and I would prefer a receiver that could listen to other frequencies as well. Any suggestions? Thanks Malcolm
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Deleteif person 1 and person 2 broadcast on the same channel at the same time but only person 1 has the CTCSS code set
ReplyDeletewould person 3, using the same channel and code as person 1, also be able to hear person 2 (i.e. because the code is being broadcast)
In that case the two transmitting radios would interfere. Usually the receiving radio will hear the stronger radio but if they are both about the same signal at the receiving radio then neither will get through properly
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