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r d
.....
' " "
Q)
Ul
.qi
I.!)
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r -
-
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N
-
NOTE
:
(Cont
'
d)
on the oscilloscope.
Referring
to
t
he
reference
lin
e a
s a
"go
-
no go"
mark, non
-
technical personnel
can
rap
i
dly
run
equipment
through test.
c.
Recheck the zero reference {step 8c
o
n p
ag
e 17}.
S
i
n
gle -
F
requency Operation
- -
I
n
almost all
microwa
ve measurement syste
ms
cer
tain
err
or signals are
prese
n
t
.
When a
reflectometer
system c
a
n
b
e
operat
e
d at a
sin
g
l
e fr
e
quency
,
most of th
ese
error
signals can be
compe
n
sated for by the
use of certa
in
addi
tional
equipment.
Even without the use of such additional
equipm
e
n
t, some
advantage in
accuracy
i
s g
a ined in single
-
frequency operation, bec
a
u
s
e
th
e M ode
l 416A
c
an be
calibrated
exactly to the
value
of a
k
nown reflection coefficie
n
t instea
d
of the
b
es
t
obtainable
average, as
in
broadband
operati
on.
One
of th
e
error
signals
present
in a
reflecto
me
ter
s
ystem
is
t
h
a
t
due
to
imperfect d
i
rectivity
of
the
d
irectional
coupler.
The
Hewlett-Pack
ar
d 752 s
eri
es
o
f
dir
e cti
o
nal
couplers
have a high directivity
{ratio
of
forwa
r
d
t
o
reve
r
s
e
p owe
r
)
of 40 db o
r better
,
but
even
with such high directivity the m agnitu
d
e
of the reverse
signal
is
important when measuring low
reflection coeffic
i
e
nts
.
By
t
he u
s
e
of a
slide s
crew tuner and a moving
load,
the directivity of t
he
reflec
ted di
re
ctional
c
ouple
r c
an
be made infinite at a single frequency.
When t
h
i
s t
echni
que is
used,
it
may
b
e performed before or after calibration.
With the
s lide sc
r
ew tuner prope rly
adjusted,
the reflected directional
coupler
becomes a
coupler
with
infini
t
e
directiv
i
ty
at the
single
frequency of interest.
The
procedure
for
c
ancelin
g
o
ut t
h
e
directivity
er
r
or is d
e
s
cribed under
Adjustment of Slide Screw
Tun
er, below.
N
OTE: (l} Setup
procedures
for single-freque
n
c
y o
pera
t
i
on
are
the sarne
as
that
described above
for
broadband
o
p
er
at
i
on
e
x cept that no
c
onnection
need be made between t
h
e M odel 41
6
A
and the ver-
tical input
on a d
-
c oscilloscope.
{2} Equipment
specified
in
the followin
g
proce
d
ure
s
i
s
u
sed when
operating
in
the
X band.
For
operatio
n
i
n
the
S b
a
nd
,
procedure
is the
same;
equipment
to be
used
is specifie
d
i
n Setup (S
Band},
below
•
Calib
r
a
t ion at Single
Frequency
with
Fixed
Short
T
o calibrate
with a fixed
short
( 100%
r
eflection),
procee
d as d
e
s
cr
ibed
under C
a
l
ib rati
on
(100% Reflection,
Broadband), above, mo
d ifying s teps
1, 3,
and 6 a
s indicated
belo
w.
NOTE
:
Calib
r
a
ti
on with
a
sli
d
i
ng
short
i
s the
more a
c
curate
me
thod
.
1.
On
the Model
670H
(or
HM) oscillator
:
a.
Set
the FREQUENCY
-
KMC
dial
for the desired
frequency.
b.
Set the
SELECTOR switch at the MANUAL
position.
3.
On
the
Mode
l
670H {or HM)
,
adjust
the
ATTENUATION
con
tr
o
l
while
watching
the tuning eye on the
Model 416A.
The ATTE
N
UA
T
I
ON control
should
be
adjusted to
obtain
an
approximately
1 /8
11
gap
in
t
h
e
tuning
eye shutte
r
.
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20-
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