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TM
11-5820-919-40-1
to exactly 10 kHz.
The  divided  signal
2 - 6 7 .High  Frequency  Loop  Filter.
will agree with the 10-kHz Standard and
High  frequency  loop  filter  U2  divides
the VCO tune voltage will remain con-
the  0.69-3.49  MHz  from  the  prescaler
stant.
If the divided frequency is
according to the code on the bcd fre-
below  the  10-kHz  Standard,  it  will
quency  select  pins.
Table 2-8 gives a
cause the VCO tune voltage to increase.
few  examples,
After  the  high  frequency
If the divided frequency is above the
loop filter U2 has completes its divi-
10-kHz  Standard, it will cause the VCO
sions,  it sends a Reset Pulse back to
tune  voltage  to  decrease.
prescaler  U4.
If the VCO is tuned, the
0.69-3.49  MHz  signal  should  be  divided
HIGH
FREQUENCY
LOOP
DIVISION
CODE
Input Pin
Control  Panel
No.
44
43
Frequency  kHz
Divisions
42
41
40
39
38
37
36
35
-
-
-
-
-
-
-
-
S1(100)  +S2(10)
+S3+49
69 (20 + 49)
2,000
0
0
0
0
1
0
0
0
0
0
10,000
149 (100 + 49)
0
0
0
0
0
0
0
1
0
0
15,100
200
(151
+49)
0
1
0
0
0
1
0
1
0
1
209 (160 + 49)
16,000
0
1
0
0
0
0
1
0
1
0
29,900
1
0
348 (299 + 49)
1
0
0
1
0
1
1
0
S1 is 10-MHZ digit, S2 is 1-MHz digit, and
0 = ground
S3 is 100-kHz digit on the control panel
1 = open (+12v pullup)
3.
The output of the mixer U6 is
of 77-105 MHz LO With FREQUENCY KHZ Set
70,000 kHz plus or minus 94.3 kHz.
to  15,184.3.
This  example  summarizes
The  filtered  product  which  reaches
the operation of the 77-105 MHz LO.
the VCO at pin 15 is 70,000 kHz
Table  2-9  lists  the  equations  from
plus 94.3 kHz or 70,094.3 kHz.
which  any  FREQUENCY  KHZ  setting  can
be  figured.
4.
The output of the mixer within
the VCO U3 is 90,184.3 kHz (the
The output of the LO is 75,000.0
1.
LO) plus or minus the 70,094.3
kHz  from  the  mixer  U6).  The  minus
kHz  above  the  FREQUENCY  KHZ  set-
product  reaches  the  prescaler  U4
ting.
This is 15,184.3 kHz plus
at 0,090.0 kHz.
Note that the XY
75,000.0  kHz  or  90,184.3  kHz.
(4.3) kHz digits have been mixed
The output of the low frequency
out  by  the  correct  LO  output.  In
2.
phase lock is 90.0 kHz above the