100-kHz reference frequency. Also, the front IF subassembly (BS) mixes the 4.350-
to 4.449-MHz signal (from subassembly 36) with another oscillator frequency. It,
too, is phase locked to a multiple of the same 100-kHz pulses we have just
discussed.
From this, another 390-to 399-kHz frequency is developed.
The two
nearly identical but separate frequencies of 390 to 399 kHz (one from the reference
frequency and the other from the VFO output frequency) are compared by a
discriminator in subassembly B5.
If a frequency or phase difference exists, an
error voltage is developed and applied to the VFO (B2).
STUDY EXERCISES
In each of the following exercises, select the ONE answer that BEST completes
the statement or answers the question.
Indicate your solution by circling the
letter opposite the correct answer in the subcourse booklet.
1. The primary function of a frequency synthesizer is to furnish all or most
conversion frequencies needed by a radio set. A secondary function is to
a.
regulate all voltages in the radio set.
b.
attenuate all noisy frequencies received by the radio set.
c.
provide additional amplification of weak signals when needed.
d.
stabilize all operating frequencies furnished by the synthesizer.
2.
A frequency synthesizer is often used in a transceiver to
a.
disable the radio transmitter during reception.
b.
disable the radio receiver during transmission.
c.
allow both the transmitter and the receiver to operate at the same time.
d.
furnish identical
conversion
frequencies
to
the
receiver
and
the
transmitter.
3.
The output signal of the indirect-class synthesizer is derived from a
a.
crystal oscillator.
b.
stabilized master oscillator.
c.
variable-frequency oscillator.
d.
combination of crystal oscillators.
327 L2
23
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