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skc_assy_041722.pdf
Schematic
General design notes:
Tx keying output from chip is active high. The 2N7000 mosfet is supplied to invert the signal as most
rigs key and mute with active low signal. It also allows for switching voltages greater than the 5 volts the
SKC operates at.
R1 controls the volume of the function tone sent to the speaker/earbud. We supply 100 ohm resistor for
max. volume. Do not use a value less than 100 ohms. At 2.2K resistor the volume gets faint.
C2, 3 and 4 are required for static protection and help de-bounce the switch and paddle inputs.
Connect the “Function Tone” pad to your audio output device, so you can hear the function prompts.
Both voltage and temperature will affect the clock speed. For proper side tone pitch and keyer speeds,
the supply voltage must be near 5 volts and be stable, hence the 78L05 regulator. The input voltage is
7-15VDC max.
You do not hear your code on the "Function Tone" pin. The function tone pin is only for feeding audio of
the functions into your audio chain so you can program the keyer for speed changes or messages. If
your are testing the keyer for operation, hook it up to your transceiver. Alternately, you can put an led in
series with a 10K resistor from the keyer output to +V and you will see it flash as you send code. Make
sure you have the polarity correct for the led.
Notes:
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