CRYSTAL SWITCH A2000 - TM-11-5820-670-300022

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)

CRYSTAL

OSCILLATOR

FREQUENCY

NUMBER

Y2007

46.950

MHz

0.05 or 0.10

0.15 or 0.20

Y2008

47.050

MHz

0.25 or 0.30

Y2009

47.150

MHz

0.35 or 0.40

Y2010

47.250

MHz

0.45 or 0.50

Y2005

47.350

MHz

0.55 or 0.60

47.450

MHz

Y2004

0.65 or 0.70

Y2003

47.550

MHz

47.650

MHz

0.75 or 0.80

Y2002

0.85 or 0.90

47.750

MHz

Y2001

0.95 or 0.00

46.850

MHz

Y2006

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