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.
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