Fluke 6080A - Page 207

TROUBLESHOOTING AND REPAIR
FREQUENCY AND PHASE MODULATION
The active feedback network consists of a second op-amp U38 and resistors R99 and
R95, and is functional for switching from ACFM to LOWRATE-FM. The selected
feedback network is controlled by the analog switch U36 for the different modes of
operation. The Z5, U35 range selection has a 16 to 1 magnitude relationship and is
selected in conjunction with the Z7, U32 combination. The Z5, U35 combination is
also selected relative to ACFM or PHASE-MOD.
Table 6E-1 shows the relationship between selected modulation ranges and functions
for inputs, controls, and outputs. Table 6E-2 shows the relationship between the
modulation ranges and the FM DAC values.
Table 6E-2. Modulation Ranges and FM DAC Values
6E-9
FM DAC = (FM Deviation * Mult)/1111
6
5
4
3
2
1
0
512-1056
4.00 MHz
1.01 MHz
mult= 1
1.00 MHz
251 kHz
mult= 4
250 kHz
62.6 kHz
mult= 16
62.5 kHz
15.7 kHz
mult= 64
15.6 kHz
3.91 kHz
mult= 256
3.90 kHz
0 Hz
mult=1024
256-512
2.00 MHz
501 kHz
mult= 2
500 kHz
126 kHz
mult=8
125 kHz
31.3 kHz
mult= 32
31.2 kHz
7.82 kHz
mult=128
7.81 kHz
1.96 kHz
mult=512
1.95 kHz
0 Hz
mult=2048
128-256
1.00 MHz
251 kHz
mult 4
250 kHz
62.6 kHz
mult= 16
62.5 kHz
15.7 kHz
mult= 64
15.6 kHz
3.91 kHz
mult= 256
3.90 kHz
977 Hz
mult= 1024
976 Hz
0 Hz
mult=4096
64-128
and
.01-15
500 kHz
126 kHz
mult= 8
125 kHz
31.3 kHz
mult= 32
31.2 kHz
7.82 kHz
mult= 128
7.81 kHz
1.96 kHz
mult= 512
1.95 kHz
489 Hz
mult=2048
488 Hz
0 Hz
mult=8192
32-64
250 kHz
62.6 kHz
mult= 16
62.5 kHz
15.7 kHz
mult= 64
15.6 kHz
3.91 kHz
mult= 256
3.90 kHz
977 Hz
mult=1024
976 Hz
245 Hz
mult=4096
244 Hz
0 Hz
mult=16384
15-32
125 kHz
31.3 kHz
mult= 32
31.2 kHz
7.82 kHz
mult= 128
7.81 kHz
1.96 kHz
mult=512
1.95 kHz
489 Hz
mult=2048
488 Hz
123 Hz
mult=8192
122 Hz
0 Hz
mult=32768
CW MODE