Comtech EF Data CDM-625 - Manual (Page 167)

CDM-625 Advanced Satellite Modem Revision 15
Front Panel Operation MN-CDM625
5–67
5.2.2 SELECT: Test Menus
TEST: Mode BERT ()
CnC-APC-Monitor Uncorrected-BER
Use the ◄ ► arrow keys to select Mode, BERT, CnC-APC-Monitor, or Uncorrected-BER, and
then press ENTER.
5.2.2.1 SELECT: TEST  Mode
Modem Test Mode = Normal ()
(NORM,Tx-CW,Tx-1/0,IF↓,RF↓,DIG↓,I/O↓)
Select Normal Operation or a Test Mode from the parameters shown in the parentheses. Use
the ▲▼ arrow keys, and then press ENTER, to select one of the following modes:
Selection Function
NORM
(Normal) This c lears any t est modes or l oopbacks, and pl aces t he uni t bac k i nto an
operational state.
Tx-CW
(Transmit C W) Use t his test m ode to f orce t he modulator t o t ransmit a pur e c arrier
(unmodulated).
Tx-Alt-1/0
(Tx-1/0)
(Transmit an al ternating 1, 0,1,0 p attern) Use t his test mode t o c heck t he carrier
suppression of the Modulator This mode forces the modulator to transmit a carrier modulated
with an alternating 1,0,1,0 pat tern, at the currently selected symbol rate; t his causes two
discrete s pectral l ines t o appe ar, s paced at ± half t he s ymbol r ate, about t he c arrier
frequency.
IF-LOOP (IF↓)
(IF Loopback) Use this test mode to invoke an i nternal IF loop. This is a par ticularly 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 th ose of t he t ransmit s ide. All pr evious values ar e restored onc e Normal is agai n
selected.
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 t he 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.
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 pas ses 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.