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NOTE
:
By us
ing a waveguide
-
to
-coaxia
l
adapter (suc
h
as
a
Hewlett
-Packard
Model
281A Waveguide
to
Coaxial
A
dap
ter),
a
coaxial
slotted line, such
as a
Mode
l
805A
(or B)
Slotted
Line
or
Mod
el
806B Coaxial Slotted
Sec -
ti
on, may
be used
with
t
h
e
Model 809B
ca
rriage.
A
ratio
met
er
such
as
the Model 416A
Ratio
Meter.
A
coaxial
-
to
-
waveguid
e
a
dapter (
s
u
ch as
the Model
281
A) to connect
the signal
source to the waveguide
.
Descr
i
ption
-
Th
e
following
is a
general
descr
ipti
on
of
slotted-line
system
connections
,
operating conditions,
and
cal
ibration
procedures
when
the Model
416A
is
used
as
the indicator
.
Step-by-step
operating
instructions
are given follow
i
ng
this
general descr
i
ption
,
under Operating
Procedure.
NOTE
:
When
the
sequence
of
instruction
s give
n in
Operating
Proce
-
du
re is followed
exactly, t
h
ere wi
ll
be little
danger
of over
<•
loading
t
h
e
ratio meter or
the
dete
ctors,
As
indicated
in
Fig
.
16,
the
trans
m
ission
sy
stem, w
hich
i
ncludes a
directional
c oupler
a
nd
s
l
otted line,
is
terminated
by
the
load under
meas
-
urement
.
The
output
from
the secondary
arm
of
t
h
e directiona
l
coupler is
connected to
a
square
-
l
aw
detec
tor
(eithe
r crystal
or b
arre
t
ter)
which,
in
turn,
is connected
t
o the
INCIDENT /REFERENCE
input on
the
Model
416A.
The output
of
the s
lotted
-
line probe
is connected
to another square-
law de
-
tector
,
and,
at the time
the
standing
-wave
ratio
is measured
,
the
output of
this detecto
r is
c
onn
ected
to th
e
REFLECTED/PROBE
i
nput on the
Model 416A
.
A
microwave
osc
i llator
is
arranged
to
deliver
t
o th
e
tra
nsmission sys
-
tem
an rf
signal
modulated
by
a 1-kc square-wave voltage.
The signal is
sam
-
pled by the
directi ona
l
co
upl
er, and
the
1-kc
enve
l
ope
subsequently is
detected
by the
detecto
r.
The detector
output voltage
is
proportio
nal
to
the
output from
the signal
sour
ce, and is
used
as
a reference
voltage
b
y
the ratio
meter
.
The calibration
p
r
o
cedure involves
adj
ustments
w
h
ich
result,
at the
Model 4
16A, in
a
l
;
1 ratio between
th
e referenc
e
voltage and
the
maximum
standing
-wave voltage,
F
irst the probe
in the
slotted line
is
move
d
along
the
line until
t
h
e standing
-wave
maximum
point is found.
Then the
amplitude of
the
voltage
picked
up
b
y
the
prob
e is
regulated by
adj
u sting
probe
depth
of
penetration
.
When
the
indication on the
Mode
l 416A meter (upper
SWR scale)
is
as close
to
"1"
as
adjustment
of
probe penetration
can bring
it,
the ratio
meter SET
TO
FULL
SCALE
control (which adjusts
the amoun
t of gain in the
Model
416A probe
channel)
is adjusted to bring the meter
indication exactly
to" 1
11
,
which
indicates a 1: 1 ratio between
the
voltage
in
the Model
416A
reference
channel and the voltage
in
th
e
Model
4 16A p
r
obe
c
hannel.
By
this
two
-
fold procedure
( 1) regulating amplitude
by adjusti
ng the
proportion of
volta
ge
c
oupled
into
the
probe
detector and ( 2)
setting the
gain
in the Model
416A
prob
e
channel
to exactly
the
a mount requi
red
to
bring the
amplitude of
the
v oltage
i
n
the
probe
channel
to the
same
level as
that
in
the
-3
9
-
!.
-
-
, ,
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