Icom IC-H6 Service Manual page 24

AF
Millivolt-
meter
AF
Oscillator
Dummy
Load
3. Modulation check
Power
Supply
{8.4V)
0
Directional
Coupler
Maximum deviation: With 1KHz 120mV shall be 4.5KHz ±10%.
Deviation
Meter
Modulation sensitivity: Mic input voltage 12mV ±3d8 at 1 KHz. Deviation should be 3.5KHz.
S/N Ratio:
Connect the output of the deviation meter to a millivoltmeter. With no audio input to the mic
input, take the voltmeter reading. Now apply 1KHz40mV audio into the mic connector. Take
the voltmeter reading. The ratio should be greater than 40dB.
C. Spurious Transmission
Connect spectrum analyzer with appropriate attenuation. Confirm nearby random spurious signals
below fundamental frequency less than -60dB.
Measure the harmonic wave output, adjust R F-ATT until noise level just appears.
Should be less than -60d8 below the fundamental frequency.
7 · 5- 3 RECEIVER
A. LO Output Adjustment
•Set the channel select switch at a programmed channel (center frequency of the frequency range is
recommended). Adjust L217 and L218 for maximum output on an RF voltmeter attached to
R257.
•Then set the channel select switch at a high edge frequency channel and adjust L217 and L218
with the same procedure.
•Repeat above procedures to obtain the same reading on the RF voltmeter on either channel.
The output voltage should be about 200mV.
B. RF IF DET Coil Adjustment.
1. The connecting point of measuring instrument and the setting of the knob.
•Set the channel select switch at a programmed channel.
•Connect a signal generator to the antenna connector.
•Connect an external speaker and AF millivoltmeter to the EXT SP terminal.
2. Procedure
Set RF voltage meter (minimum range) to Pin 16 on IC101 in the IF, adjust l101 through L105
maximum output while setting the input from the signal generator as low as possible. Then vary
the input frequency from the signal generator ± 10KHz. Check if rippling (change in output
level) occurs. If ripple is over 3d8, readjust L 105.
Set signal generator output to -80dBm to -90dBm and deviation to 3.5KHz. Set signal
generator frequency to speaker output maximum. After that, adjust L 107 for maximum output.
3. Confirmation
Sensitivity should be less than -8dBµ (0.4µV) for 20dB quieting.
7-8