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

5.2.3 SELECT: Test

TEST:
Use the arrow keys to select Mode, BERT, or Comp, and then press ENTER.
5.2.3.1

TEST: Mode

Modem Test Mode = Normal
(Norm,Tx-CW,DSB,SSB,IQ PN, F,IF Dig, /0)
Use the arrow keys to select Normal modem operation or to select an available Test Mode,
and then press ENTER to execute. Available selections are as follows:
Selection
Norm
Tx-CW
DSB
SSB
IQ PN
IF
F
IF Dig
/O
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) This mode should not be enabled over the satellite.
Two carriers on both sides of the nominal center Tx Frequency, whose frequency difference is
equal to the configured Tx symbol rate.
(Single Side Band) This mode should not be enabled over the satellite.
This mode demonstrates the modulator's carrier null, amplitude, and phase balance. 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 mode transmits random unframed data to the Nyquist filters. Use this 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. It is a particularly useful test in that it
permits the user to perform a quick diagnostic test without having to disturb external cabling.
Furthermore, all receive configuration parameters are temporarily changed to match those of
the transmit side. When Normal is again selected, all previous values are restored. See Figure
5-2 for the flow diagram for this test.
(RF Loopback) Use this mode to perform a satellite loopback. It is almost identical to the IF
loop mode, except that 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. When Normal is again selected, all previous values are restored. See Figure 5-2 for the
flow diagram for this test.
(Digital Loopback) This mode tests the entire interface, transmit baseband circuits, and buffer.
It 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. See Figure 5-2 for the flow diagram for this test.
(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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