Comtech EF Data CDM-600/600L - Manual (Page 267)

CDM-600/600L Open Network Satellite Modem Revision 3
Appendix H MN/CDM600L.IOM
H–3
Whenever MIX = “–” the spectrum of the carrier is inverted. The CDM-600L easily corrects for
this with the Invert ON/OFF selection located under the CONFIG:TX ÆTX-IF and CONFIG:
RX: ÆRX-IF menus.
Match the Tx inversion to the MIX in the BUC and the Rx inversion to the MIX in the LNB
using the following:
• Spectrum = Normal when MIX = “+”
• Spectrum = Invert when MIX = “–”
As a general rule it is best to radiate the spectrum toward the satellite in the Normal spectral
sense. Then transmission links with any other corresponding sites are always consistent at the
satellite interface.
When doing RF loopback testing over the satellite or end-to-end the settings are correct with this
setup. If there is a single inversion in the modem, however, for operation over the satellite, it will
be necessary to temporarily match the spectral inversion of modulator and demodulator when
performing IF loopback testing.
Note: The modem will only allow configuration of terminal frequencies that are within its valid
L-Band frequency limits.
H.4 Applying Power To The BUC
CAUTION
1. Care should be exercised in cable installation. Install the cables using the most
direct route and secure with clamps and ties. Avoid all sharp bends.
Replacement of the cables can be the result.
2. If the ODU voltage is not correct, DO NOT connect the Tx-IF Cable to the
modem or damage may result. Contact Comtech EF Data Customer Service
department.
3. Ensure Tx and RX L-Band cables are not connected. After the modem is
checked out, then configure to operate with the ODU.
4. Initially, set LNB and BUC current wide enough to avoid false reports during
installation. Readjust the limit at a later time.
5. For FSK operation with an FSK capable BUC see Chapter 5. FRONT PANEL
OPERATION and Appendix H. CDM-600L BUC FSK COMMUNICATIONS.
Complete Steps 13 through 29 prior to continuing.
The conditions for the BUC to function are as follows:
• Proper Tx L-Band power to the BUC from modem.
• Sufficient and correct DC power at the BUC.
• 10 MHz reference supplied to the BUC.
Note: To ensure proper performance, Comtech EF Data recommends a 5-minute warm-up period
at initial turn-on for the BUC. This can be accomplished by performing Steps 15 through 18, prior
to initiating the power start-up.