Figure 4-6. Regenerative Divider, Simplified Schematic Diagram

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TO 31R2-2GRC171-2
TM 11-5820-815-14
NAVELEX 0967-LP-544-5010
Figure 4-6. Regenerative Divider, Simplified Schematic Diagram
are in the frequency range of one-half the vco frequency
4-81. To maintain regeneration over the range of the
are amplified by Q4 and applied to the local oscillator
three voltage-controlled oscillators, varactor CR2 tunes
port of mixer Z1. Mixer Z1 mixes the vco frequency with
the output tank circuit (T2 and CR2) of Q4 to one-half the
the frequency present at the local oscillator port to
center frequency of the frequency band enabled.  For
produce a difference frequency at the if output. For this
high-band vco frequencies (320 to 400 MHz), varactor
circuit to be stable, the frequency present at the if output
tuning voltage (about 13 V dc) developed across R40 of
must be equal to the frequency applied to the local
voltage divider R37-R40 is applied through resistor R30
oscillator port. This occurs only when the if output is
to the cathode of varactor CR2.  This decreases the
exactly equal to one-half the vco frequency.  (Vco
capacity of CR2 causing the resonant frequency of T2
frequency mixed with one-half vco frequency equals one-
and CR2 to be approximately 180 MHz. For midband
half vco frequency.) As a result, for any vco frequency
vco frequencies (250 to 320 MHz), the logic 1 midband
applied, the circuit locks up and becomes regenerative at
decoder output voltage turns midband switch Q6 on.
one-half the vco frequency.
This connects R38 in parallel with R40 to reduce the
varactor
tuning
voltage
to
4-19
TO 31R2-2GRC171-2

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