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For
the
dual-display modes, the
horizontal
switch
switches
the horizontal input between the
synthesizer
!;weep
and the character sweep.
This
switching
is
5imultaneous with
that
in
the
scope vertical control,
as
described in
paragraph 9.2.2. The horizontal
switch
control
also provides
the SCOPE
MODE
EN
line
to
the
!;COpe amplifier
to
enable
the
horizontal inputs for the
!;COpe
mode.
9.2.4
SYNTHESIZER SWEEP
CONTROL
The
control
circuitry
for the synthesizer sweep
(Ufi2B and
U52C)
controls
the
amplitude and
range
of
the synthesizer's sweep-generator
signal.
Two sweep
ranges,
1
to
10 MHz
and 0.01 to
1 MHz, are provided
hy
the
control circuitry.
The
control circuitry
has
two
fixed attenuations of
1.0 and
0.1.
The variable
sweep
range
i!;
provided by
the
dispersion
sweep control on
the front
panel. To
contr
ol
the
bottom
range of
the
sweep,
a
10-to-1
resistor
change
in the
sweep
return
line
is
simultaneous
with
the
attenuator
change.
9.2.5
SCOPE Z-AXIS CONTROL
The
SCOPE
Z-AXIS
s ignal has
th
r
ee possible
5(•urces, as
selected
by
the
Z-axis
control
circuitry
(U55,
U6
1A
and U61B).
For
character
displays,
t he
Z-axis
signal is the
CHAR
GEN Z-AXIS from the
character
generator
on
A14
.
For
the
scope
mode,
the SWP
BLANKING
signal
from the horizontal timebase
gen-
erator
on A2 is
switched
to the
scope
Z-axis.
For
the
remaining
modes
(spectrum
analyzer and
scope
sweep),
a
logic
zero
level
is gated
to the
Z-axis input.
9.2.6
MODULATION-DISPLAY
CONTROL
The
select circuitry
for
the
internal
scope
and
peak
detector
<U20A,
U20B. and U20C) switches
the
DEMOD
CAL
AUDIO
,
AM
CARRIER
+
MOD
LEVEL.
or MOD
CAL AUDIO
signals
to the internal
scope and
peak
detectors.
The
signals
are
gain adjusted
by
processor
select
before
exiting t
he
module from the
l
NT
SCOPE
TOR G
SW output.
For
F'M,
the MOD
CAL
AUDIO input
from the
Audio Synthesizer board (A10) is calibrated to
5
kHz/\' for narrowband and to
20
kHz/V
for
wide band.
These signals
are
gain
adjusted by gain amplifier U23B
to a level of25 kHz/V and
become the
INT
SCOPE
TO
HNG
SW
output.
The
DEMOD
CAL
AUDIO signal
from
the Receiver
is
either
AM, FM,
or SSB, as
determined
by
the oper-
ati
ng mode. The peak signal
on this line is calibrated
9-2
to
10 kHz/V
for
FM and
10 percent/V
for AM. These
signals
are gain adjusted
by
gain
amplifier
U23B
to
a
level
of 25
kHz/V
and 25 percent/V. This gain
-adjusted
signal becomes the INT
SCOPE TO
RNG
SW output.
SSB
signals
are not
calibrated.
For
AM,
the
CARRIER
+
MOD LEVEL input from
the
output detector on
t
he Wideband
Amplifier
board
(A17
A2) provides
a
direct
display
of
the
modulation.
This
input
is
a
de-level representative
of the average
output
level,
plus an ac
signal representative
of the
amplitude mod ulation on
the
output.
For
the
scope's
modulation
display, the
de
level
is blocked
by
C49
so
that
only
the
ac component is observed.
This
input
is
uncalibrated
for
absolute
ac levels. The percent
of
AM
is
determined from the
peak
ac and average de
level
of
the CARRIER
+
MOD LEVEL signal. The
average
de
signal
is obtained by a low-pass filter (U19).
9.2.7
PEAK
DETECTOR
Each of the
modulation
and
demodulation
inputs
can be
switched
to the
peak-detecting
circuitry
(U21-
U2:1,
U26, U54) to
determine
the
percent AM
or kHz
deviation. The
peak-detector circuitry
provides
de
outputs
equal
to the
negative
and positive peak
values
of
the input signal. These peak
values are relative to
the average
de level
of the input
signal. The de levels
are then
digitized
by
the DVM
and input to the Pro-
cessor.
9.2.8
DVM
CONTROL
Any
one of
nine
internal measurement
points
may
he
switched
to
INT DVM
TO
A/D.
This
signal
is
routed
to the
Processor
Interface
board
(All) where it
is
multiplexed
with external DVM data to the input
of
the
analog-to-digital
(A/D)
converter.
In
general, sev-
eral
internal
measurement
points
must
be input to the
AID
converter to
obtain
all
the
display
data. There-
fore,
the
processor continuously cycles
the
Internal
DVM Select
switch
(U20D and
U28)
through the
required measurement
points,
stopping
at
each one
long
enough
to
digitize
and
input
the data to the
pro-
cessor.
The
Internal
DVM Select
switch
is followed by a
ran!{e
attenuator
(U29
and Q5). As the
processor cycles
through each
input,
it sets
the
range
attenuator
according
to the
last cycle reading made
at
that
input.
Thus,
each internal input
is
auto-ranged
over
two
dec-
ades
to
give
3-digit accuracy
up
to
a maximum input
of
lOV.
The
internal
DVM inputs
and
thei
r
functions
are lis ted
in Table 9-1.
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