
Model 5601MSC
Model 5601MSC Master SPG/Master Clock System
Page - 22
Revision 2.2
OPERATION
In the
Abrupt
mode, the 5601MSC will respond to any change in the incoming frequency reference with
an immediate re-lock, shifting the timing of the unit to match the reference. This effect will ripple to the
outputs and may cause undesired effects in downstream equipment, depending on the amount of
correction performed. This is the default mode of operation. When the
Genlock Range
menu item is set
to
Wide
, the relocking mode is always
Abrupt
, regardless of the
Lock Type
menu setting.
When the
Slow
lock mode is selected, the 5601MSC will detect when its oscillator is not synchronized
to the reference and issue a frequency reference unlocked warning. It will display REF JAM NEEDED
on the left LCD display and can also be configured to send out an SNMP trap (see section 4.5.9.3.4). It
will then gradually adjust the frequency of the OCXO, limiting the rate of change, until the oscillator is
brought back into sync with the incoming reference. Once this “slow” re-lock process is complete, the
“REF JAM NEEDED” warning will be cleared. The Lock progress display will return to 100% and the
unit will continue normal operation.
The
Slow
lock type can take a long time to relock to the reference signal, especially when correcting for
a large discrepancy in phase. It takes about a minute to correct for a phase difference of one line of
video. At any time during this Slow relock process, the operator can force the 5601MSC to immediately
lock to the reference by performing a frequency
jam
. This can be performed by selecting
Jam
Reference
in the
Jam Input
menu off the
INPUT
root menu. It can also be performed remotely through
SNMP. Once the
Jam Reference
has been initiated, the frequency and phase from the reference is
jammed into the main oscillator, forcing it to lock immediately. Performing a
Jam
may cause
disturbances on all sync and test generator outputs as the phase of the unit is reset.
Careful consideration and testing of Slow lock mode effects should be made, especially when using
multiple 5601MSC units locked to each other. Portable truck systems that may require a cold start of all
equipment should allow for some time for oscillator warm-up and GPS lock but could require a manual
frequency
jam
to be performed in order to get units locked up quickly.
When the unit is first started up, or if the frequency reference source is changed
by the user, a frequency jam is always performed. This jam occurs even if the
Lock Type has been set to Slow mode. When locked to GPS, this initial
frequency jam could occur 5 to 30 minutes after the unit has been restarted,
once GPS lock is fully established.
If a large shift in the reference occurs while Slow lock mode is enabled, the
outputs of the 5601MSC may be out of phase for a long time while re-locking.
The 5601MSC will gradually slew its oscillator to bring it back into phase with
the reference. This slewing action combined with the apparent phase shift may
seem to indicate that the unit is completely unlocked to the reference and
freerunning. This should not be considered a fault. A manual jam can be
performed at any time to force the 5601MSC to lock immediately.
Содержание 5601MSC
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