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or ‗+‘ key (and holding it down) until you achieve the drive level you need. Adjust
deviation to achieve about 3 to 3.5 kHz deviation from your radio.
Equalization.
If you have another Kantronics user nearby, have that station transmit a calibrate
square wave and choose the R option in your calibrate mode to measure the status of
receive equalization. You will see two numbers displayed each time you press R. The
KPC-3 Plus is measuring the space/mark square wave generated by the other station.
For best performance, these numbers should be about equal. A 40/60 to 60/40 ratio is
acceptable. Change jumper J4 if need be. Default is no equalization, since it‘s normally
not needed.
Note: If you are using a High Impedance Data output from the radio, set J3 on one pin
only (OFF = 10 kΩ, ON = 620 Ω).
PTT (Push-to-Talk) Watchdog Timer
The KPC-3 Plus has a built-in PTT Watchdog Timer. The PTT output will be disabled if
the TNC has been continuously transmitting for more than approximately 3 min.
To disable the Watchdog timer, jumper the pins of J12.
Microprocessor Watchdog Timer
The TNC includes a watchdog timer within the microprocessor. In the unlikely event that
your TNC firmware gets into an infinite loop, the watchdog timer will detect the failure
and force a reset of the TNC.
A/D Converter
Two A/D converter inputs are available to the KPC-3 Plus and are used with the Analog
command. These inputs can be used to measure dc external voltages from 0 V to 5 V
dc with up to 8-bit accuracy.
Note: If you want to measure voltages greater than +5 V dc, the signals need to be
attenuated (by installing resistors R13 or R27 on the printed circuit board) to divide them
down in voltage. Choose resistance values to scale the desired input voltages to 5 V dc
max at test points ―J‖ or ―K‖ on the printed circuit board.
It is possible to bring external voltage into the onboard A/D converters from either the
Radio Port or the Serial Port using Jumpers J8 or J10. (See the ―jumpers‖ section.)
So, if you jumper the A/D inputs via this port (instead of the RS232 port) you cannot
utilize the A/D inputs and control line outputs at the same time.
Note: Maximum input measurement can be made. Maximum input voltages to the
A/D inputs should not exceed 50 V or damage may occur.
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