Comtech EF Data CDM-625A - Manual (Page 200)

CDM-625A Advanced Satellite Modem MN-CDM625A
Front Panel Operation Revision 3
6–74
6.2.2 SELECT: Test Menu Branch
TEST: Mode BERT ()
CnC-APC-Monitor Uncorrected-BER
Use the ◄ ► arrow keys to select a test parameter. Press ENTER.
6.2.2.1 SELECT: TEST  Mode
Modem Test Mode = Normal ()
(NORM,Tx-CW,Tx-1/0,IF↓,RF↓,DIG↓,I/O↓)
Use the ▲▼ arrow keys to select Normal modem operation. Press ENTER. Otherwise, select a
Test Mode from the parameters shown in the parentheses. Valid selections are:
Setting Function
NORM
(Normal) This clears any test modes or loopbacks, and places the unit back into an
operational state.
Tx-CW
(Transmit CW) Use this test mode to force the modulator to transmit a pure carrier
(unmodulated).
Tx-Alt-1/0
(Tx-1/0)
(Transmit an alternating 1,0,1,0 pattern) Use this test mode to check the carrier
suppression of the Modulator This mode forces the modulator to transmit a carrier modulated
with an alternating 1,0,1,0 pattern, at the currently selected symbol rate; this causes two
discrete spectral lines to appear, spaced at ± half the symbol rate, about the carrier
frequency.
IF-LOOP ( IF↓)
(IF Loopback) Use this test mode to invoke an internal IF loop. This is a particularly useful
feature, as it permits you 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. All previous values are restored once Normal is again
selected. See Figure 5-3.Starting with Firmware Ver. 1.3.1, IF Loopback now works
correctly when Carrier-in-Carrier is enabled.
RF-LOOP (RF↓)
(RF Loopback) Use this test mode to perform a satellite loopback. It is almost identical to the
IF loop mode, except that all receive configuration parameters (except Rx Spectrum Invert)
are temporarily changed to match those of the transmit side; however, no internal connection
is made. All previous values are restored once Normal is again selected.
Dig-Loop
(DIG↓)
(Digital Loopback) Use this test mode to invoke a digital loopback, which loops data at the
output of the Reed-Solomon encoder on the transmit side and back into the Reed-Solomon
decoder on the receive side. This tests the entire interface, transmit baseband circuits, FEC
encoder, FEC decoder, and buffer. See Figure 5-3.
I/O-Loop (IF↓)
(Inward/Outward Loopback) Use this test mode to invoke 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. See
Figure 5-3.