Lesson 005

FREQUENCY READOUT / COUNTER

FOLLOW EACH STEP BELOW USING YOUR SCHEMATICS.
IN THIS LESSON, WE'LL POWER UP AND
CALIBRATE THE FREQ COUNTER.


1.  Connect the input of the FC to ground.  You can use a short
    jumper clip lead or solder the loose end of R1 to ground.
    Adjust the contrast control R5, the 1k pot to center position.
    Apply 12 volt power to the regulator IC.  +12 goes to the
    left leg in the picture.  The display should show something.
    Check to make sure that nothing is getting hot, except maybe
    the 180 ohm 2 watt resistor used to limit the current to the
    backligh LED.  If you have a display and nothing is getting hot,
    adjust the 3 pots, R6, R4 and R3 until you get a "0" reading.
    All pots will be either fully clockwise or counterclockwise.

2.  Obtain a calibrated frequency source. It should be greater than
     1 MHz and less than 30 MHz.  If you don't have an accurate source,
     use the output of a known QRP transmitter.

    Unground the input to the FC and connect to the Freq source.
    Adjust the vari-cap C6 until it displays the correct frequency.
    Reconnect the FC input to ground.

3.  Adjust the pot connected to pin 1 on the PIC chip until the LCD
    shows about 4.913.  Next adjust R3 and the R4.  The pots need to
    be adjusted to display the transmit BFO frequency, which is about
    4,913,700.  We'll fine-adjust these pots later after the transceiver
    is built.

NOTE:  The schematic descriptions for R3, R4 and R6 are wrong.
       R6 is the course freq offset adjust
       R3 is the medium freq offset adjust
       R4 is the fine freq offset adjust

THIS COMPLETES THE MP20 FREQUENCY DISPLAY/COUNTER

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