Select: Test; Test: Mode; Test: Bert - Comtech EF Data CDM-750 Installation And Operation Manual

CDM-750 Advanced High-Speed Trunking Modem
Front Panel Operation
5.2.2.2

Select: Test

TEST:
◄ ►
Use the arrow keys to select Mode, BERT, or Comp, and then press ENTER.
5.2.2.2.1

TEST: Mode

Modem Test Mode = Normal
(Norm,Tx-CW,DSB,SSB,IQ PN, F,IF Dig, /0)
Per the following table, use the ▲ ▼ arrow keys to select Normal modem operation or one of
the available Test Modes, and then press ENTER to execute:
Selection
Norm
Tx-CW
DSB
SSB
IQ PN
IF
F
IF Dig
/O
The IF, Digital, and I/O Loopback Test modes are illustrated in Figure 5-2.
Mode BERT
Description
(Normal) This clears any test modes or loopbacks, and places the unit back into an operational
state.
(Transmit CW) This mode forces the modulator to transmit a pure carrier (unmodulated).
(Dual Side Band) Two carriers on both sides of the nominal center Tx Frequency, whose
frequency difference is equal to the configured Tx symbol rate.
Note: This mode should not be enabled over the satellite.
(Single Side Band) A single carrier on one side of the nominal center Tx frequency, offset
from the nominal carrier frequency by half of the configured symbol rate. This demonstrates the
modulator's carrier null, amplitude, and phase balance.
NOTE: This mode should not be enabled over the satellite.
This mode transmits random unframed data to the Nyquist filters. This mode should be used to
measure spectral mask as there is no correlation due to framing or terrestrial data patterns.
(IF Loopback) This mode invokes an internal IF loop. This is a particularly useful feature, as it
permits the user to perform a quick diagnostic test without having to disturb external cabling.
Furthermore, all of the receive configuration parameters are temporarily changed to match
those of the transmit side. When Normal is again selected, all of the previous values are
restored.
(RF Loopback) This mode is almost identical to the IF loop mode. All of the receive
configuration parameters (except Rx Spectrum Invert) are temporarily changed to match those
of the transmit side. However, no internal connection is made. This is useful for performing a
satellite loopback. When Normal is again selected, all of the previous values are restored.
(Digital Loopback) This mode invokes a digital loopback, which loops data at the output of the
framer on the transmit side, back into the framer on the receive side. This tests the entire
interface, transmit baseband circuits, and buffer.
(Inward/Outward Loopback) This mode invokes two distinct loopbacks. The first is the inward
loop, which takes data being received from the satellite direction, and passes it directly to the
modulator. Simultaneously, the outward loop is invoked, whereby data being fed to the transmit
data interface is routed directly back out of the receive data interface.
Comp
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