Icom IC-H6 Service Manual page 9

3- 4- 2 LED INDICATOR CIRCUIT
This LED is lit in the transmit mode, but when the power supply voltage becomes less than 7V, it will
not be lit.
The power supply voltage is divided by R148 and R149, and applied to the base of 0121. The emitter
of 0121 is connected to the regulated 6V source. When the power supply voltage is more than 7V,
0121 is turned OFF, 0122 is turned ON and T+6V is applied to the LED through 0122 and R150, and
the LED is lit.
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DIODE MATRIX BOARD
The set incorporates a diode matrix board to determine its operation frequencies, and six channels each
can be programmed into the board for transmit and receive.
+6V is applied to each channel line, one of receive channels 1 - 6 and transmit channel 1 - 6, through
the channel select switch, and it is converted to BCD codes by diodes programmed into the board, then
fed to IC201 to determine an operation frequency.
When duplex transmit function is required, calculate each N value for transmit frequency and receive
frequency and program diodes into the board independently.
The receive only function is provided for channel 2 - Channel 6 by inserting a diode into the receive
only line. At this time, a voltage is applied to the base of 0107 on the MAIN board through R404, and
it turns 0107 ON and 0106 OFF. Thus, the set does not turn to the transmit mode, even if the PTT
switch is depressed.
Crystal Frequency Chart
Operating Frequency Range
Crystal Frequency (MHz)
Local Oscillator
X202 (Receive) X203 (Transmit)
Frequency (MHz)
150.005 - 155.000MHz
32.02625 36.25125 145.005
155.005 - 160.000M Hz
33.27625 37.50125 150.005
160.005- 165.000MHz 34.52625
38.75125 155.005
165.005 - 170.000M Hz 35.77625 40.00125 160.005
NOTE: The local oscillator frequency for calculation N value is the four times of the crystal frequency.
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