Model 8642A/B
Operation
Modulation, $M (cont'd)
Example
Phase modulate the RF output with an external, 1 Vpk, dc-coupled source, 2 radians <!>M
deviation, at a rate determined by the external source's frequency. V.-,
1
LOCAL
(keys)
(program
codes)
{ SHIFT
j
ENTRY
*M
MODULATION SOURCE
IEXTDC]
( SHIFT |
ENTRY DATA
UJ\JD
PMXD PM 2 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
10
0.0 00000/nz
FREO
r2.0 0 R U
*M EXT
-IW0.0
HIT?
DC AMPTD
The RF output is being externally phase modulated with an external dc-coupled source
(as indicated by the *M, EXT, and DC annunciators). <I>M deviation setting is 2.00
radians per volt. Modulation frequency is not monitored by the Signal Generator when
an external modulation source is used. The cursor above the *M setting indicates $M is
the active function.
HP-IB
Codes
Keys
*M
MOD FREQ
INT
EXT AC
EXT DC
INT+ (EXT AC)
Codes
PM
MF
PMNT
PMXA
PMXD
PMBA
Keys
INT+ (EXT DC)
OFF ON
rad
kHz
Hz
SPCL
Codes
PMBD
PMOF,
PMON
RD
KZ
HZ
SP
Comments Modulation Types Not Possible During RF Frequency Sweep
During Stepped Frequency Sweep, FM and 4>M are allowed in manual or single sweep
mode only. During Phase Continuous Frequency Sweep (Special Function 123), all
modulation types are allowed.
Modulation Switching Time
The time required to turn on the internal modulation oscillator or to switch between
modulation frequencies can be reduced by approximately 200 ms (depending on modula-
tion frequency), with a loss in modulation frequency accuracy, by selecting Modulation
Frequency Correction Off (Special Function 113). For more information, refer to
"Speeding Up Modulation Switching Time" on page 3-1 32.
3-123
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