The G8TMV CTCSS encoder board Rev 1
The board comprises a voltage regulator, an MSP430 micro controller to generate the tone output
and control the functionality of the system, an active filter to turn the voltage
ladder into a sine wave and a pot to allow setting of the output level, plus a few
ancillary parts to make it all work.
There is provision for a control button, an led and a PTT input.
The encoder is designed to run from 5 - 12v and draws approx 9mA. It makes sense to have
the supply line switched so that tones are not generated during simplex operation.
The tone output is only active when the PTT input is grounded.
The tone encoder can generate any of the 10 standard CTCSS tones used
by the U.K. repeater system.
Each time the control push button is pressed the encoder moves to the next tone
in the sequence. Each time a new tone is selected, and at power up, the LED annunciates
the code letter for the tone in morse code.
A tone can be made the default by pressing and holding the push button until the LED
flashes once. This stores the currently selected value in the micro controller
non-volatile memory so that it will be used the next time the encoder is powered up.
The tones and their code letters are:
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A | 67.0Hz
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B | 71.9Hz
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C | 77.0Hz
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D | 82.5Hz
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E | 88.5Hz
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F | 94.8Hz
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G | 103.5Hz
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H | 110.9Hz
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J | 118.8Hz
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S | 100.0Hz
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All of the rev 1 boards are sold.
Errata
Due to a PCB track error the level pot works backwards, turning it clockwise decreases
the output level.
