Model 8642A/B
Operation
Modulation,
$M
(cont'd)
Example
Phase modulate
the RF
output using
the
internal modulation oscillator
at a 10 kHz
rate,
with
1
2
radians
4>M
deviation.
LOCAL
(keys)
(program
codes)
[
SHIFT
]
ENTRY
*M
[JMJ
DATA
CD DO GO
MODULATION SOURCE
(JNTJ
I
SHIFT
I
ENTRY
*M
i
m
I
ENTRY
I
MOD
I
[
FREO
]
DATA
QDCE
CL)
PMNT
MF 10 KZ PM 12 RD*
* These codes
are not
independent
and
might need
to
follow
a
specific sequence
for
entry.
Refer
to the
discussion about Sequence Dependency, which begins
on
page
3-12 in the
HP-IB portion
of
this Section
III.
Display
CTOU.FP IB.ZBWZ IZ.BRH -fWS.BUJT]
The
RF
output
is
being internally phase modulated
(as
indicated
by the 4>M and INT
annunciators).
$M
deviation
is 12.0
radians. Modulation frequency
is set to 10.00 kHz.
The cursor above
the "I'M
setting indicates that
$M is the
active function.
EXT
AC, EXT DC
How
to Set $M
with
an
External Source
Source
fcAUTI£Nl
Do
not
apply more than
1
5 Vpk
maximum external voltage
to the
FM/$M INPUT
or
damage
to the
Signal Generator's circuitry could
result.
The external modulation source connects
to the
FM/'i'M INPUT connector (input
impedance
of 600
ohms).
The external modulation signal level should
be
adjusted
to a 1 Vpk
(0.707 Vrms)
sinewave input
to the
Signal Generator
to get an
actual
$M
deviation equal
to the
displayed
4>M
deviation.
For
example,
if a 1 Vpk
external modulation source
is
provided,
with
the
Signal Generator's
$M
deviation
set to 50.0
radians
per
volt,
the
output
has 50.0
radians
4>M
deviation.
(If the
source voltage
is
reduced
to 0.5 Vpk, and no
other settings
are changed,
the
output
has 25.0
radians 4>M deviation.)
3-121
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