HP 8753D - Page 129

Frequency
Oset
Mode
Operation
Frequency
oset
measurements
do
not
begin
until
all
of
the
frequency oset
mode parameters
are
set.
These
include
the
following:
Start
and
Stop
IF
Frequencies
LO
frequency
Up
Converter
/
Down
Converter
RF
>
LO
/
RF
<
LO
The
LO
frequency
for
frequency
oset
mode
must
be set
to the
same value
as
the
external
LO
source
.
The
oset
frequency
between
the
analyzer
source and
receiver will
be set
to
this
value
.
When
frequency
oset
mode
operation
begins
,
the
receiver locks
onto the
entered IF
signal
frequencies
and
then
osets
the
source
frequency
required
to produce
the IF
. Therefore
, since
it
is
the
analyzer
receiver that
controls the
source,
it is
only
necessary
to
set
the
start
and
stop
frequencies
from
the
receiver
.
Dierences
Between
Internal
and
External
R-Channel
Inputs
Due
to
internal
losses
in
the
analyzer's
test
set,
the
power
measured
internally
at
the
R-Channel
is
16 dB
lower than
that of
the
source
.
T
o
compensate
for
these
losses
,
the
traces
associated
with
the R-Channel
have been
oset 16
dB higher
.
As
a
result,
power
measured
directly at
the
R-Channel
via
the
R
CHANNEL
IN
port
will
appear
to
be
16
dB
higher
than
its
actual
value
.
If
power
meter
calibration
is
not
used,
this
oset
in
power
must
be
accounted
for
with
a
receiver
calibration
before
performing
measurements
.
The
following
steps
can
be
performed
to
observe
this
oset
in
power:
1.
T
o
set
the
power
range
to
manual,
press:
4
MENU
5
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N
N
N
POWER
N
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N
N
N
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N
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N
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N
PWR
RANGE
MAN
4
0
5
4
x1
5
Setting
the
power
range
to
manual
prevents
the
internal
source
attenuator
from
switching
when
changing
power
levels.
If you
choose a
dierent power
range
,
the
R-channel
oset
compensation
and
R-channel
measurement
changes
by the
amount of
the attenuator
setting.
2.
Connect
the
analyzer
source
output, port
1, directly
to the
R-channel input
as
shown
in
Figure
3-3
.
Caution
T
o
prevent
connector
damage,
use an
adapter (HP
part number
1250-1462) as
a
connector saver for R CHANNEL IN.
Figure 3-3. R-Channel External Connection
3-4 Making Mixer Measurements