For Amateur radios, repeater access tones are essential for retransmission and propagation of signals. Unless a certain tone is caught, the retransmission of the signal from the receiver to the transmitter does not occur. However, there’s more to it that you must take note of!
What is the repeater access tone?
In an amateur radio system, repeater access is introduced for the repeaters to indicate them to activate when required. This system uses a simple burst of tone at the beginning of the transmission, which would be specific to a repeater.
This tone is about a few seconds long and of a particular frequency that makes it’s identification clear. An audio filter is installed at the repeater, which can extract the given tone and decipher if the tone is the one that is allotted to the repeater.
Only on receiving the set tone for the radio, the ham repeater becomes active, and the process continues with the transmission. So, to cut it short, a repeater access tone is an activation controller tone for the amateur radio repeater.
Why do you need repeater access tones?
You must be wondering that if the purpose is just to activate the repeater for use, why don’t we simply allocate a specific frequency to it? Well, with the surge in the number of repeaters, it has become a necessity to re-use the channels we have.
Thus, when several repeaters are located nearby to other repeaters and transmitters, signals can get intermixed. This intermixing of signals can further undergo intermodulation and generate false signals.
The intermodal waves might appear at the repeater’s input and get retransmitted, thereby disturbing the communication. For avoiding such unlikely retransmission, a repeater access tone is useful for verifying and activating the channel.
How to set the repeater access tone?
A certain repeater access tone can have one out of the 38 possible frequencies. All of these are below 300 Hz and have unique tones. Your ham radio will have a tone-key or menu selection that contains the list of all the available tones.
You can select the tone you prefer for your ham radio and add it to the transmitted signal. Other than this, you might also be able to set your radio’s squelch to use a specific CTSS tone for more security.
The repeaters filters out the tone squelch before the retransmission of the given signal. This way, only the designated devices receive the signal, and privacy is well-maintained. DCS or Digitally Coded Squelch can also come handy for higher security requirements according to the project.
To sum up
In two-way ham radio, you can assign a specific repeater access tone to receive the exact signals that are meant for you. This makes your connection to the rest of your group strong, reliable, and void of any false or mixed signals.
The better the quality of the signal transmission, the more convenient and efficient a channel becomes. For a project that requires top-security or privacy, you can also use CTSS or DCS techniques.