Internal Freq Ref:) Adjust; Internal Freq Ref:) Warm-Up Delay - Comtech EF Data CDM-570A Installation And Operation Manual

6.3.7.3.1

(Internal Freq Ref:) Adjust

Internal 10 MHz Freq Ref
Fine Adjust:+017(◄ ►,▲ ▼)
For fine adjustment of the Internal 10 MHz reference oscillator, use the ▲▼arrow keys to edit the
value. The valid range of values is from –999 to +999.
In order to facilitate adjustment, the value updates in real time as the digits
increment/decrement. You do not need to Press the ENTER key.
The numbers displayed here do not correspond to an exact frequency
increment. You should perform this fine adjustment while using an external
frequency counter, connected either for:
•
or
•
6.3.7.3.2

(Internal Freq Ref:) Warm-up Delay

Warm-up delay:
Enable
Because the modem uses a high-stability oven-controlled 10 MHz reference Oven-controlled
Crystal Oscillator (OCXO), the modem requires a finite time period for the oven to reach operating
temperature. Consequently, when the modem first powers up, a frequency error as great as 2 x 10
will occur, and it may take up to 2 minutes before the frequency settles to its correct value. This
affects the Tx synthesizer (and hence the Tx output frequency), the Rx synthesizers, and the
generation of the Internal Tx baseband clock.
For a modem operating on its own, this may not be a problem, but if you use the 10 MHz reference
signal to drive an externally connected BUC, the frequency error at the RF output may be large,
particularly at Ku- or Ka-Band. In order to avoid this problem, you may choose to enable a warm-up
delay, which suspends normal operation of the modem until the operating temperature of the OCXO
stabilizes.
Warm-up delay is not fixed. Instead, the modem uses an intelligent algorithm to minimize this delay,
under all circumstances. The modem uses its internal temperature sensor and knowledge of how
long you have powered down the modem to determine the duration of the warm-up delay period.
For example: The worst case occurs when the modem has been powered down sufficiently long
that the modem has achieved ambient temperature, and the external temperature is at the lowest
value possible. Under such conditions, the modem will take two minutes to warm-up.
If the external temperature is hot, and you power down the modem only to power up again a short
time later, the warm-up period is very short, perhaps only several seconds.
Front Panel Operation
CDM-570A/570AL Satellite Modem with Optional Packet Processor
The internal 10 MHz reference, if you have internal access to the
equipment,
The Tx Output, set for CW, 0 dBm output level, and an exact center
frequency (e.g., 1000 MHz).
Disable
(◄ ►,ENTER)
6–65
Revision 5
-6
MN-CDM570A