Have you ever been on a 4×4 trip and found that you can’t find a clear channel that you and your mates can get on? Or is it all nice and quiet apart from a smart ass on the other side of town who every now and then jumps on with an interesting noise mid conversation.
Well, mid 2011 year, the powers that be are expanding the UHF range of frequencies available to the public which effectively means that we’ll get a full 77 channels to play with. So does that mean you should dump your old 40 channel UHF radio as your tour leader is now running on channel 60? Well, no, why don’t you just convince him to use the CTSS / DCS function that comes with most CB radios now days.
CTSS stands for “Continuous Tone-Coded Squelch System”.
DCS stands for “Digital-Coded Squelch”.
Despite the cryptic names, the CTSS / DCS functions are actually very easy to use, most of the newer CB radios have them, and they can provide you and your team with effectively an uninterrupted radio channel without much effort at all.
In laymen’s terms, switching on CTSS basically causes your UHF radio to listen out for, an analogue ‘SQUELCH’ as an undertone which is inaudible to the human ear with every transmission. Similarly it will also send this ‘SQUELCH’ with every transmission you make.
Now, with CTSS there is a range of 38 different ‘SQUELCH’ tones that can be used across every available channel on the UHF range.
DCS is exactly the same except the ‘SQUELCH’ is a digital signal as opposed to being analogue. With DCS you have a total of 104 different ‘SQUELCH’ signals available again per channel.
On the 40 channel system we have about 38 channels available for transmission. With 38 CTSS options and 104 DCS options on each channel, you effectively have 38 x (38+104) = 5396 combinations to choose from to find a quiet channel to share between you and your mates.
Using CTSS and DCS
If you can use your microwave, you can use CTSS / DCS on your UHF radio. It’s simple.
For this demo, I’m using my Uniden 500SX (40 channel) which is set in a din slot within my trusty old GQ Nissan Patrol. (Don’t mind the mud) Other recent UHF CB Radio brands and models work in a very similar way.
First up, tune to an available channel on your UHF radio. For this demo, we’re going to use channel 20.
Next, we’re going to hit the ‘DCT/CTSS’ button.

The CTSS logo lights up and it displays ‘oF’ telling us that CTSS is off.
Then simply use the dial as you would with a channel and the small number switches over to your desired CTSS ‘SQUELCH’ tone. In this case I’m setting it to 10.
Then, Bob’s your uncle. Tell your mates to set their UHF radio to channel 20 – CTSS 10 (for example) and you’ll be listening and transmitting on channel 20, but all the background noise will be filtered out as your radio will ignore anything that doesn’t have a ‘SQUELCH’ tone of 10 transmitted along with it.
To use DCS (the digital ‘SQUELCH’ levels), simply turn the dial past CTSS tone 32 and it’ll start on the DCS signal numbers from 1 to 104. Same thing, tell your mates to go to channel 20 – DCS 95 (for example) and more often than not, you’ll have a nice and quiet channel to yourself and your group.
To switch CTSS / DCS off, simply turn the dial back to off and you’ll be back and listening to the open channel.
Quirks with using CTSS / DCS
You’ll find that when you switch over to using CTSS you need to just give it half a second before speaking into your mic after hitting the transmit button.
This is because your radio needs to start sending the ‘SQUELCH’ tone and the other radios need to pick it up before they decide that it’s the right code and start outputting it to the receivers’ speaker.
On DCS the problem is a little more pronounced and I’ve found that the Uniden’s are a little sensitive with DCS so you need to take a longer amount of time before speaking after hitting the transmit button to make sure the message gets through.
Have fun, and happy four wheel driving!
Muz
TORQ4x4
TORQ4x4 sell a great range of Uniden 4×4 UHF CB Radios which are 77 channel ready and include both the CTSS and DCS ‘SQUELCH’ capability.























