Mocomtech CDM-QX - Manual (Page 116)

CDM-Qx/QxL Multi-Channel Satellite Modem with DoubleTalk™ Carrier-in-Carrier® Revision 7
Front Panel Operation MN/CDMQX.IOM
5–50
5.6 (MAIN MENU:) Test
TEST: Mode BIST (◄ ►,ENT)
Spec-Analyzer
Select Mode, BIST (Built-in System Test), or Spec-Analyzer using the ◄ ► arrow keys, then
press
ENTER
.
5.6.1 TEST: Mode
Mode: Norm IF2 Dig2 I/O2 RF2
Tx-CW Tx1-0 SSB-CW (◄ ►, ENT
All test modes are available if grouped as a modem. However, in ungrouped cases – e.g., Tx only –
Norm, Tx-CW, and Tx1-0 are the only selections. For Rx only, it is always in Norm.
Select Norm, IF Loop, Dig Loop, I/O Loop, RF Loop, Tx-CW, or Tx-1,0 using the ◄ ►
arrow keys, then press
ENTER
. Note the following:
Norm
(Normal) This clears any test modes or loopbacks, and places the unit back into
an operational state.
IF Loop
(IF Loopback) This test 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. During an IF
Loop, the Tx carrier continues to be transmitted. See Figure 5-3.
Dig Loop
(Digital Loopback) Not supported due to the different card configurations in the
chassis.
I/O Loop
(Inward/Outward Loopback) This test mode invokes two distinct loopbacks. The
first of these 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.
RF Loop
(RF Loopback) This test mode is almost identical to the IF loop mode. All of the
receive configuration parameters 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.
TX-CW
(Transmit CW) This is a test mode, which forces the modulator to transmit a pure
carrier (unmodulated). Used for measuring phase noise.
TX-1,0
(Transmit an alternating 1,0,1,0 pattern) This is a test mode that 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. This mode is used
to check the carrier suppression of the Modulator.
SSB-CW
(Single-sideband CW) The test will produce a spectral pattern suitable for the
measurement of SSB rejection – useful in determining the phase and amplitude
accuracy of the modulator.