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,,
'
Slotted Lines
- -
General
-
The magnitude
of the reflection
coefficie
nt
of a load
may be
ascertained by measuring the
standing-wave
ratio
and applying
the formula
i
+I
p
I
i
-
I
P
I
SWR, where
I
f
I
is the
magnitude
of
the
reflection
coefficient.
Techniques
which may be
used in
mea
suring
standing
wave ratios, pos
~
sible sources of error, and general precaution
s
to
be observed in setting
up
and operating a slotted-line system are d
isc
ussed
in
texts such as Terman
&:
Pettit
'
s Electronic Measurements
and
i'n
instruction literature
on slotted-line
sections such as the Hewlett
-
Packard
Model
806B Coaxial Slotted Section
.
Instructions given
in
this section
are limited to those
which are spe-
cific
to
the use of a Model 416A
in a
slotted~line
system.
Equipment
-
A typical assembly
of devices for
measuring standing-
wave ratios, using
the
Model 416A
Ratio Meter
as
the indicator,
is
shown in
Fig. 16
.
Such a slotted
-
line system
should
i
nclude
:
A source (with
modulating capabilities) ·of signals
in the
frequency range
in
which
standing
-
wave ratios
are to be rneasured
0
Accurate
,
stable signal
genera-
tors
such as Hewlett
-
Packard
Models 612A, 614A,
616A
,
618B and
620A are suitableo
Or
a
Model 670
SHF Oscillator and Mod
el
717A Klystron
Power Supply
may be used
as a signal sourceo
A dire
c
tional
coupler and a
square
-
law
detectoro
In
the 2.6-kmc to
18.0
-
kmc
range
9
a
high
-
directivity
series of couplers
such as the Hewlett
-
Packard
Model
752
Directional
Coupler series
is
suitable,
The
asso-
ciated detector may
be
either a
barretter or crystal
detector
0
For
the 8.
2 -kmc
to
12
0
4
-
kmc range,
a
Hewle
tt-
Packard
Model X421A
Crys
tal
Detector
Mount
is
available" and for the
2. 6
-
kmc to 3
0
95
-
kmc
range
,
the barretter
-eq
uipp
ed
Model
S485A
Waveguide
.
Detecto
~
·
,
,
.
'
"-'
·
·
_.
,lj.;
Mount
is
availableo
While
t
hes
e
excellent,
higli
-
qu;ility
detectors
ar~
recon1.mended,
satisfactory perf
ormance,
in
gerrer
i3.l'
; '
'
1
M
the
ratio
meter
may be
obtained
when
other
crystal d.etectors
are used in the referenc
e
channel.
NOTE
:
It is to
be noted
,
however, that
for
accurate
indication
by the Model 416A
,
the
detector
in the
probe
c
hannel
must be
a
high-quality. true
-
square
-
law
d
evice.
A
slotted
-
line
section
.
A
suitable
low
-
reflection waveguide
slotted
-
line
section
m
ay
be
a
s
sembled
by using a
Hewlett
-
Packard Model 809B
Universal Probe Carriage,
Model 810
Waveguide Slotted Se
ction, and e
i
ther a
Model
444A Untuned
Probe or a Model
440A Detector Mount fitted with
a Model 442B
Broadband Probe.
-
38
-
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