Specifications
TM 11-5820-670-30
1-16. CRS SECOND MIXER A3300 AND CRYSTAL SWITCH A2000.
(CONT)
SECOND MIXER A3300
The second mixer performs a signal heterodyning function, mixing the output of the 53 MHz filter with a
frequency from the interpolation oscillator.
Within the mixer module is a tuned tank circuit which couples the mixer’s output to first and second if.
amplifiers A3400. The tank circuit is tuned to resonate at 5.625 MHz so that frequencies near 5.625
MHz are coupled, while frequencies below and above tank’s half-power points are severely
attenuated.
CRYSTAL SWITCH A2000
Crystal switch A2000 contains two crystal-controlled oscillators, the interpolation oscillator and
reference oscillator. The reference oscillator is discussed in paragraph 1-18.
The interpolation oscillator’s output frequency is controlled by one of 10 possible crystals which are
selected by a switch through the action of the radio’s gear train. Each crystal corresponds to two
positions of the radio’s tuning controls out of 20 possible 50 kHz increments that can be selected
between whole-number frequencies. For example, in tuning from 30 to 31 MHz, the tuning controls
select frequencies of 30.05, 30.10, 30.15, 30.20, 30.25, etc. The first two steps (30.05 and
30.10) correspond to a particular crystal in the crystal switch. The next two steps (30.15 and 30.20)
have a different corresponding crystal. This pattern repeats itself until all 10 crystals have been
individually selected. When the frequency selection controls reach 31.00 MHz, the same crystal is
selected as was used for 30.00 MHz.
The following table lists 10 pairs of radio dial frequencies between each whole-number setting, the
number of corresponding crystal, and the interpolation oscillator’s frequency when that particular
crystal is selected.
RADIO DIAL DECIMAL (kHz)
FREQUENCY
0.05 or 0.10
0.15 or 0.20
0.25 or 0.30
0.35 or 0.40
0.45 or 0.50
0.55 or 0.60
0.65 or 0.70
0.75 or 0.80
0.85 or 0.90
0.95 or 0.00
CRYSTAL
NUMBER
Y2007
Y2008
Y2009
Y2010
Y2005
Y2004
Y2003
Y2002
Y2001
Y2006
OSCILLATOR
FREQUENCY
46.950 MHz
47.050 MHz
47.150 MHz
47.250 MHz
47.350 MHz
47.450 MHz
47.550 MHz
47.650 MHz
47.750 MHz
46.850 MHz
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