HP 8753D - Page 124

7. T
o enter
the relative
velocity of
the cable
under
test,
press:
4
CAL
5
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MORE
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VELOCITY
FACTOR
and
enter
a
velocity
factor
for
your
cable
under
test.
Note
Most
cables have
a relative
velocity of
0.66 (for
polyethylene
dielectrics)
or
0.7
(for
teon dielectrics).
If you
would like
the
markers
to
read
actual
one-way
distance
rather than
return
trip
distance
,
enter
one-half
the
actual
velocity
factor
. Then
the
markers
will
read
the
actual
round
trip
distance
to
the
reection
of interest
rather
than
the
\electrical
length"
that
assumes
a
relative
velocity
of 1.
Vel
ocity F
actor =
1
p
"
r
where 
r
is the
relative
permittivity
of
the
cable
dielectric
.
8.
T
o
position
the
marker
on
the reection
of interest,
press:
4
MARKER
5
and
turn
the
front
panel
knob
or
enter
a
value
from the
front
panel
keypad.
In
this example
,the
velocity factor
was
set
to
one-half
the
actual
value
,
so
the
marker
reads
the
time and
distance to
the reection.
9.
T
o
position
a
marker
at
each
reection
of
interest,
as
shown
in
Figure
2-56
,
press:
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MARKER
2
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MARKER
3
N
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NN
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MARKER
4
,
turning
the
front
panel
knob
or
entering a
value from
the
front panel
keypad after
each
key
press
.
Figure 2-56. Device Response in the Time Domain
Making Measurements 2-75