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CR4301. Capacitor C4348 allows an attenuated sample of the
generator signal to enter the receiver circuit.
The first amplifier is dual-stage, consisting of field-effect
transistors Q4301 and Q4302, filter FL4302, inductors L4302,
L4303, L4304 and L4307, and related resistors and capacitors.
The amplified signal is then connected by coupling transformer
FL4303 to the bandpass filters. After bandwidth filtering, the
signal is connected by coupling transformer FL4304, for isola
tion, to the second amplifier consisting of field-effect tran
sistor Q4311, coupling transformer FL4305, inductor L4306 and
related capacitors and resistors. An AGC, using transistors
Q4304 and Q4305, controls the gain through Q4301, Q4302 and
Q4311.
0-40V FROM
DIGITAL FREQ COUNTER
FM MOD
_,
AM MOD
GEN COMMAND FROM GEN AUDIO
10.7 M Hz
_
TOI
FROM
IF MODULE
-
-
,.
••
-.f)
�
/10.7 MHz RECEIVER MODULE
,.
AM
MOD-
+2
ULATOR
200KHz
���
15 KHz
�
-'�
I
,>c....l
•
6 KHz
AGC FROM REC EIVER AUDIO BD
���
7
-
21.4 MHz
vco
t
--
,
..:..2
AM
-
-
DEMOD
-
- L,,.
'
FM
DEMOD
Figure 7-8 Receiver/Generator Block Diagram
D. BANDPASS FILTERS
DE MOD AUDIO
TO REC AUDIO
10.7 MHz
TO DIGITA L
FREQ ERROR
COUNTER
DEMOD AUDIO
TO REC AUDIO_
-
The three bandpass filter circuits each utilize an RF tran
sistor, two crystal filters, and two isolation diodes. The
three circuits are identical except for resistor values and the
bandwidths of the crystal filters. When a bandwidth is selected
on the Modulation Mode Selector Switch on the Front Panel (i.e.,
AM NAR), a +12 VDC command is applied to the appropriate filter
7-38
Summary of Contents for FM/AM-500
Page 152: ...DETAIL A 11 Figure 6 6 Dual vco 6 14 01 Assembl Y ...
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