CTCSS Explained

this is a short video to explain ctcss and dcs tone encoding on your two-way radios if you have the midland walkie-talkies you may have noticed that they were advertised with 142 privacy codes well they're not really privacy codes but uh ctcss and dcs are what they're advertising now ctcss stands for continuous tone coded squelch system this is an analog function dcs stands for digital coded squelch which is of course a digital function both of these systems do exactly the same thing but in the ect we use ctcss because the analog function will be found on pretty much every two-way radio now first a word about squelch what exactly is squelch well the squelch is a circuit on your radios that mutes the receiver output in the absence of a detectable carrier frequency in other words when the radio is not receiving an incoming transmission without the squelch your radio would sound like this that would get up your sleeve pretty quickly and it would also drain your battery so again the squelch mutes your radio receiver output when it is not detecting an incoming signal it turns the speaker off basically when there's no traffic on the selected channel frequency and when another station presses their ptt button the radio generates a carrier frequency which is then modulated by their voice and this is what's called frequency modulation or fm now when this carrier frequency is detected by your radio your radio opens up its squelch circuit and you hear their transmission come through this is why we wait a brief instant after pushing the ptt before we speak it gives the receiving station a chance to open up their squelch circuit before you begin speaking so your transmission isn't clipped now ctcss is just a different kind of squelch when we program our radios to use ct css it adds a continuous low frequency tone to our voice transmissions and it tells our radios to keep the squelch circuit closed unless it detects that same low frequency tone on an incoming signal it's like a two-way pass key basically for opening up the squelch circuit and these tones are very low in frequency and they're easily filtered out by the radios so we don't hear them when we're transmitting or receiving but our radios detect them very easily so if one group of stations are all using the same ct css tone on a given channel then they will hear each other but they will not hear the transmissions of other nearby stations on the same channel if they are not using the same ct css tone okay so how is that going to work in in real life so we have four radios here the two radios here do not have ct css tone programmed in while the two over here do have ctcss programmed in this radio currently does not have ctcss programmed into it so what you'll see is when i push the push to talk button on this radio these two radios will open up their squelch to receive the signal but these two will not wqwp 394 radio check okay you could see over on these two radios you saw the little tx appear in the upper left hand corner indicating that they were receiving a transmission but these two radios did not receive okay so now we have the ctcss tone programmed into the transmitting radio now watch carefully what happens with these four radios when i transmit this time wqwp 394 radio check okay now that time importantly you saw that of course the two radios programmed with the same ct css tone opened up their squelch however the two radios that don't have ctcss also opened up their squelch okay that's why they're not private that's why privacy is a is the wrong word to use here the idea here is that these two radios are simply waiting for a carrier frequency so when i transmit with my ct css tone it of course includes a carrier frequency that's all these two radios need to open up these radios of course are waiting for that specific tone so when they hear that tone they open up their squelch okay the idea here is that when we're using ct css tones we're not having a private conversation any radio that is on that channel on that frequency will hear our transmissions the difference being that those of us using the cts ctcss tone will not hear the transmissions of the other stations nearby who are not using it so now why would we use ctcss tones well there are only 22 frequencies available to the frs and gmrs systems uh from the fcc so there's a limited number of frequencies that all users have available to them and what we find is is that a lot of businesses uh gardening crews landscapers construction crews that should be using and paying for business radios on business frequencies are simply illegally using the gmrs frequencies for business so that means that especially during work hours monday through friday monday through saturday really these gmrs channels have a lot of traffic on them now that doesn't come into play for most of our stations because most of our stations are using the midland walkie-talkies we're down in the canyon somewhere and we're not really getting access to those illegal signals from outside of the canyon but some of our zone leaders are up on ridges and they have antennas up on the roof and they have much more powerful more sensitive radios so they're picking up these signals from the valley and from the basin and it presents quite a problem in trying to even conduct a practice net now these stations will probably not be operating illegally during an emergency but we also don't know what other stations will come on the frequencies in an emergency uh people who just happen to have radios in a drawer somewhere turning them on and trying to find if anybody's on the air so we've decided to use the ctcss tones on certain channels the upper channels 16 through 22 in particular because those are the higher power channels and those are the channels that our zone leaders are using to communicate with each other and with me we're also using them in zone seven on channel seven on the zone primary channel because that particular area is uh exceptionally vulnerable to the illegal signals uh coming from outside of the canyon now there's a separate video explaining how to uh program your radios to put the ctcs tones in so you can check that video out um elsewhere on the uh on the channel here um but that's basically it that's the idea behind the ctcss tones why we use them and hopefully have a better understanding of how they work now if you don't if they still have any questions of course you all know how to reach me hit me via email give me a call in the cell and i'll be sure to straighten out as soon as i can okay thanks for tuning in and uh enjoy your rest of your day

Channel: LC ECT Laurel Canyon Emergency Communications Team

Views: 10,630

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Id: _9v0y0gDceM

Length: 7min 38sec (458 seconds)

Published: Sat Feb 13 2021