(1) The 1-kHz oscillator, Q1, generates a frequency from 6,525 to 6,534 kHz in
l-kHz steps.
(2) The 10-kHz oscillator, Q2, generates a frequency from 9,025 to 9,115 kHz
in 10-kHz steps.
(3) The 100-kHz oscillator, Q7, generates a frequency from 26,730 to 27,630
kHz in 100-kHz steps.
(4) The MHz oscillator, Q9, generates a frequency from 29,530 to 38,530 kHz in
1,000-kHz or 1-MHz steps.
NOTE: Further references to these oscillators will be made by their Q numbers (Q1,
Q2, Q7, Q9).
c. First Frequency Translation. The output of oscillator Q1 is applied to first
mixer Q3 where it is mixed with the output of oscillator Q2.
The first mixer
output is the sum of the l-kHz and the 10-kHz oscillator signals. The output of
the mixer is applied to 10-kHz bandpass amplifier Q4. The sum of any two selected
frequencies in the 1 kHz and 10 kHz columns in table I fall within the 15,550-to
15,649-kHz bandpass of the amplifier. This amplifier has tuned circuits (filters)
that select the sum frequencies within the 10-kHz pass band and reject undesired
frequencies and harmonics (spurious frequencies) that result from the heterodyning
process.
d. Second Frequency Translation.
Output signals of the 10-kHz bandpass
amplifier are applied as one of the inputs to the second mixer, T5, T6. The 100-
kHz signal from oscillator Q7 is applied to the second mixer as the second input
signal. The output of the second mixer is applied to 100-kHz bandpass amplifiers
Q5 and Q6. This amplifier assembly uses filters to extract the sum frequencies and
suppresses the remaining frequencies developed by the heterodyning process.
The
sum of any three selected frequencies from the 1 kHz, 10 kHz, and 100 kHz columns
in table I falls within the 42,280-to 43,279-kHz bandpass of the 100-kHz amplifier.
e. Third Frequency Translation.
The output signal of the 100-kHz bandpass
amplifier is supplied as one input to the third mixer. The output of oscillator Q9
is supplied as the second input to the third mixer.
The difference of the two
input signals is selected by the output amplifier and low-pass filter, which also
attenuates the spurious frequencies and unwanted sidebands resulting from the
heterodyning process.
The subtraction of any number in the Hz column in table I
from the sum of any three numbers in the 1 kHz, 10 kHz, and 100 kHz columns yields
a frequency that falls within the 3,750-to 13,749-kHz pass band of the low-pass
filter of the output amplifier.
Two switch positions in the MHz column are not
used; neither are two positions in the 1 kHz, 10 kHz, and 100 kHz columns.
The
output of filter FL1 (3.750 to 13.749 MHz) is the range of the synthesized
frequencies.
This synthesizer therefore obtains 10,000 frequencies in increments
of 1 kHz from a total of 40 crystals.
327 L2
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