Sierra Wireless DART 200 CDPD Modem User Manual
Page 39
DART 200 CDPD Modem User’s Guide
2 Installation and Setup
PN1197-00 Revision 1.0
2-15
If the modem stabilizes for short periods before restarting the search, the
AT&V+ output shown in Table 2-1 can be useful.
S-Register 102 contains the RSSI value in dBm. The less negative the
number the stronger the signal, for example, for CDPD 1.1:
•
Strong signals are in the range of -45 to -59
•
Good signals are in the range of -60 to -74
•
Acceptable signals are in the range of -75 to -89
•
Weak signals are in the range of -90 to -104
•
Signals below -100 are usually not dependable and can prevent the
modem from acquiring the channel
Sometimes local radio interference prevents channel acquisition. If the
BLER in S-Register 105 is above 10%, this could be the problem. Try
moving the antenna as far as possible from its current location or, if
possible, move to another location to determine if the problem can be
lessened.
Before deciding that the location is unsuitable, execute the AT&V
command and examine S-Register 60. If the 2 bit is on (usually a 5), then
the modem was set up to suppress channel searching, probably for use at
a trade show. Reset S-Register 60 to the default value of 1 with an
ATS60=1 command, and save it with an
AT&W command. If this was
not the problem, contact your carrier to discuss the lack of CDPD
coverage.
Registration
Once the DART 200 acquires a channel the next step in the initial
operation process is registration; performed by the AT\R command.
The first few times you register the modem use manual registration
(AT\R1), to get a feel for timing, and from the timing an indication of
potential problems. When registration becomes routine use continuous
auto-registration (an AT\R4 command) combined with an ATS13=0
command. Save these changes with an AT&W command, and activate
the changes by power cycling or restarting (AT-R) the modem.
This setup causes the modem to attempt to register at power on and
whenever the modem loses registration, for example, when driving out of
coverage. Registration status can be viewed by using the ATS57?
command, as shown in Figure 2-5.
Figure 2-5. Viewing registration status with ATS57?
ATS57?
161
(bits 7, 5, and 1 are on)
OK
CAUTION:
With auto-registration
active the DART can
lock up, requiring a
power cycle to clear it,
if manual registration
(AT\R1) is attempted
and the registration
fails to complete
successfully.