| Programmable
crystal controlled CTCSS tone encoder kit
It can encode the 10 UK CTCSS repeater access tones listed below + 6 extra tones, and generates a sine wave of approx 2V p-p. The tone is selected by the combination of jumpers in 4 positions, and the module is only 29 x 49mm in size. It's powered by 7 to 16V DC and draws only a few mA. There is an encode enable input that connects to the radio's PTT line (active low), and the tone select inputs are constantly read so you could change tone with a switch if desired*. You can tie the encode enable input to ground for continuous encode. Fit the 3 supplied jumpers in the following combinations to select the desired tone frequency.
The extra tones are 74.4Hz, 79.7Hz, 85.4Hz, 91.5Hz, 97.4Hz, 123.0Hz , they can be found by selecting the un-used binary combinations of the jumper field. This is a new feature. Click here for a circuit diagram in PDF format. When connecting to a radio transceiver the tone should be fed into the TX modulator after the microphone amplifier/filter/limiter and usually after the TX audio deviation control. *note that PIC pins 10,11,12 & 13 are the actual tone select inputs and if using an external switch you only need to switch some or all of these inputs to 0V (PIC pins 7, 8 & 9 are programmed to be 0V at all times). Keep any wiring from a switch to the input(s) short, it is also advisable to fit a 100 ohm resistor in series with each wire at the module end (this limits current into the PIC chips input protection circuits from static). A PDF version of this page including the circuit is available here. |
Parts list:- R1, 2, 11 10K |
