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•
A signal line
(DC IN)
from
the
rear
panel's
de-
in put port
(DC POWER)
is
brought
to
the
proces-
sor
to dete
rm
ine
ba
ttery voltage.
The voltage is
attenuated
by a
factor
of
10 to
stay
with
t he
lOY
maximum input
to
the select
switch.
The
proces-
sor
uses the
battery-voltage
measurement
to
warn
the
op
erator whe
n
t
h
e
battery
is near
its
d
is-
charged
state.
•
A rectified and
filtered
version
of
the input
to
t he
1-kHz
notch fi
lte
r
is the
last
internal measu
re-
ment
point.
This
measu rement
is
used in
calculat-
ing t
he
distortion/S INAD reading. (For furt
her
information
on t he
distortion/
SIN
AD meter
,
see
paragraph 2.10.)
•
In
the external
DVM
mode,
voltages
applied to
the
external
DVM input port
on the
front panel a re
ranged
by
processor-control over four
decades
on
t
he
Front-Panel
Interface
board
(A15). The
result
is
a 0 to 1-V
rms
signal
at
t he
output
of
the atten-
uator
fo
r
in
puts
of
0
to 300 Vrms.
The
sign al
is
routed
directly
through
the A
7
board
by t he
rms/
distort ion
-select
s
witc
h
to the
rm
s- to-dc con
-
verter
on
the
All
boa
rd.
It
is
then routed t hrough
the
interna
l/external
DVM-select
switch,
to
the
AI
D
converter,
a
nd
finally to
the
processor's
data
bus.
For
exte
rnal de
measurements,
the
ac/dc-select
switch
chooses
the
de-coupled
path
from
t
he
DVM
input
port.
A
low-pass
fil
ter
on
t he Al5
board
removes
ac
componen
ts.
The
rejection of
t
he
low-pass
filter
at
50
H
z
is
at
least
20
dB.
The rms-to -dc
converter
reads
the absolute va lue
of
t
he
de
input, and
t
he sign
detec-
tor
provides
polarity information.
For
ac
voltage
measurements,
the low-pass
fi
lter
is
re
programmed
fo
r
less t
han
1
cc
attenuation
out. to 20
kH
z.
The
ac/dc-select
switc
h
chooses
the
ac-coupled
path,
and
the
r
ms-to-dc
converter
converts
the
ac
input
into a
de
voltage eq
ual
to
the
rms
voltage of t he input.
2.1
0
DISTORTION/
SINAD METER
The
System
Analyzer
can
measure
the distortion
of
a s ignal
with
a
funda mental frequency of
1
kHz.
As
the
block
diagra
m
(Figure
2-9)
shows
at
the
end
of
the
section,
th
e
1-k Hz input
ent ers
the
DVM
input
port
t
hrough
t
h
e
ac-coupled
path
and
is
ranged
to
between
0
and
1
Vrms by
the
ranging
attenuator. The
signal
is
then routed t
hrough the
notch
fi lte
r
whe
re
t he
funda-
menta
l
frequency is
removed
.
The rms/distortion
-
select
switch
ch
ooses output of the notch fi
lter
an
d
se
nds
it
to
the
rm
s-to-dc
con
ve
rter's
input.
Here,
the
rms-to-dc
converter
measures
the
rms voltage (to 10
kHz)
of
the distortion
componen
ts.
The
inpu
t of the
notch
is
rectified
,
filte
red.
and mu ltiplied
by
1.11 (the
rms-to-ave rage
ratio
for
a
sinusoid).
The resulting
d
e
voltage
is
measured
by t
he
internal
DVM
as desc
ribed
in
pa
ragra
ph
2.9.
The processor
di
vides
t
he
rms out-
pu
t voltage
of t
he
notch
filter
by t
he
rms
input
voltage
to
th
e
notc
h
fil
te
r
to
obtain a d
istor
tion
ratio, a
nd
t
hen
co
nverts
the
distortion ratio to
dB
fo
r
the S INAD
di
s-
2-8
play.
T he
display
fo
r
percent
distortion
is
obtained
by
multiplying
the
distor
tion ratio by
100.
2.1
1
OSCILLOSCOPE
Th ree basic
functio
ns
are provided
by
the system
oscilloscope:
1)
alp ha
numeric,
2) modulation,
a
nd
3)
exte
rna
l-oscilloscope
display.
A
block
diag
ram
of
t he
oscilloscope is
shown
at
the
e
nd
of the section
in
Figure
2- 10.
Drive
signals fo
r
the
CRT
a re provided
by circuits
on
the
Scope
Amplifier
boa
rd
(A2).
Horizontal
and
ve
r
tica
l
sig
na
ls a re
ampl
ifi
ed
by t
heir
respective
a
mplifiers
from
input
levels of
0.5 V /Div to
the
levels
required
on
t he
deflection
plates.
A
Z-Axis
modula tor
circ
uit
controls
th
e
cathode-
to-grid
bias voltage
on the
CRT to
give intensity
cont
rol.
2.11
.1
HORIZONTAL INPUT
External
or internal
signals
can be
selected
for
the
horizontal-amplifier inpu
t.
External
signals
come from
the front
panel's
Ext Horiz
input
port.
Internal
s ignals
come
from
t
he
A
7
Scope/DVM
Control
boa
rd
(INT
SCOPE
H
ORlZ)
or
from
t
h
e
horizonta
l
timebase
gen
-
erator
on
t he Scope Amplifier
board
(A2).
When
either
t
he
external
input or the
time
base genera tor
is
selected,
it
is
summed
wit
h a de
signal
(HORIZ
POSITION)
whi ch
comes
from
t he
front
panel's
Horiz
posi
tion
control.
The
de
signal
controls
the
horizon
tal
position
of
t
he
!;Cope
d
isplay.
The
front
panel's
Ext
H
o
riz
input
is
applied
to the
top
o
f
the
horizontal
vernier
-gain potentiometer.
The
wiper
of
the
gain
pote
ntiometer
provides
the HORlZ
IN
P
T
s
ignal
to
the
pre-amplifier
on
the
Front-Panel
Interface
b
oard
(Al
5l.
The
pre-am
plifier
provides
the
req uired
horizontal-input
sensitivity
and
buffers t
he
signal
from
t
he select
switch
on
t
he Scope Amplifier
board.
The horizontal timebase ge nerator
provides
a
six-
decade sweep ra
nge
from
1
~sec
to 100
msec
pe
r
divi-
sion.
Control
of
t he time
base
generator
comes
from
the
front
pa
nel's
horizontal
switc
h through
t
he
processo
r.
The
I
T
SCOPE
H
ORIZ
signal
is
a sawtooth
wave-
form
which
is
provided
by t he out
pu
t
of either the
horizontal
c haracter-sweep
generator
or
the sy nthe-
sizer-sweep
ge
nerator.
A
switch
on
the
Scope/DVM
Control
board
controls
which
outpu
t is
selected
.
Dur-
ing
c haracter
d
isplay, it selects
t
he
character
sweep,
which
provides
t
he
horizontal
sweep
fo
r
the raste
r-scan
character
display. During
s
pectrum
-analyzer
a nd
RF
ge
nerator
sweep
operation,
control
of
t he INT COPE
H ORIZ
signal alterna
tes betwee
n
c
haracter
swee
p
and
:-ynthesizer
swee
p.
T
his allows the oscilloscope and
cha
rActer
informatio
n
to
be
s
imulta
neously
d isplayed
on
the
CRT.
This
also
allows
the
scope swee
p
to
be
synchronized
with
t
he RF Synthesizer
swee
p.
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