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|  TM
11-5820-919-40-1
to exactly 10 kHz.
The divided signal
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.
Example - Steady State Operation
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
addition, the prescaler input is
always 4.91 MHz above the FRE-
This is
XY (4.3 kHz digits).
90.0 plus 4.3 kHz or 94.3 kHz.
QUENCY KHZ setting. So 2.000 MHz
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