Model 5601MSC
Model 5601MSC Master SPG/Master Clock System
Page - 20
Revision 2.2
OPERATION
2.2.2. Selecting the Frequency Reference Type
The frequency reference for the 5601MSC is selected with the
Reference Src
menu item in the
Frequency Ref
menu off the
INPUT
root menu. When
GPS
is selected, the 5601MSC will use the GPS
receiver attached to the GPS port on the rear of the unit (see section 2.2.13). When set to
Ten MHz
, the
5601MSC will look for a 5MHz or 10MHz continuous wave (CW) signal on the reference loop input
BNCs (see section 2.2.12). When set to
Video
, the 5601MSC will lock to an analog video sync signal
(auto-detected) that is applied to the reference loop BNCs (see section 2.2.5). When set to
Internal
, the
5601MSC will free-run off its internal reference (see section 2.2.12.1).
The
Inputs
status screen in the
STATUS
root menu can be used to view which frequency references
have been detected by the 5601MSC. The first three lines indicate status of video sync, 5MHz or
10MHz detection, and GPS status. See section 4.1.2 for more information.
2.2.3. Selecting the Genlock Range
The
Genlock Range
menu item in the
Frequency Ref
menu selects which oscillator is used when
locking to a video sync or CW reference. When
Narrow
is selected, the high-stability oven controlled
quartz oscillator (OCXO) is used and the VCXO runs as backup. When
Wide
is selected, the voltage
controlled quartz oscillator (VCXO) is used and the OCXO runs as backup. It should be noted that when
the frequency reference source is set to
GPS
or
Internal Ref
, the genlock range is forced to
Narrow
mode (OCXO) regardless of this menu setting.
In the event that the frequency reference is lost, the 5601MSC will free-run using the selected oscillator.
The
Narrow
range OCXO has extremely high stability which will translate to very low drift. This also
translates into lower jitter on the outputs. Another advantage of the
Narrow
range is that it allows use of
the
Slow
re-lock mode that prevents glitches when re-locking to a reference (see section 2.2.4). The
disadvantages of the Narrow range are that it requires a very tight reference source (±0.1 PPM) and
requires a longer time to fully lock. The OCXO also requires five minutes of warm-up time before
reaching full stability once the unit has been powered on.
The Wide range VCXO provides very fast lock times with a wide lock range (±15 PPM) which means it
can lock to just about any reference signal. It can be useful if the 5601MSC reference source changes
frequently such as in a post-production facility. The
Wide
range cannot be used when locking to GPS or
when free-running on the internal reference. In almost all cases, the
Narrow
range is superior and
should be left as the default selection. See Table 2-3 for a summary of the characteristics of each
range.