Company Confidential
43
Raveon Technologies Corp.
14. Tune-up and Alignment
The
M8S
modem has been factory calibrated, in should not require any re-
calibration when installed, or when changing frequency or channel. Unless the
user is trained in radio test and calibration, the values stored in the R registers
should not be modified. Radio calibration and alignment is performed using the
ATRx
commands.
Improper adjustment of the radio calibration (R0-R9 and RA registers), can
result in failure of the radio modem.
Calibration and alignment values are stored internal to the modem in the “R”
registers. (R0-R9 and RA). For example, to read R5, issue the
ATR8
command
without any parameter. To change the setting, issue the
ATR8 nn
command,
where nn is the new value you would like to store.
Once you read a register using an ATRx command, you may modify its value by
entering a “U” for up or a “D” for down. U or D will change the value by one. Use
this trick carefully, because it modifies the last R register that was read, and it is
easy to unintentionally modify the wrong register.
14.1. Periodic Calibration
The only setting that may require adjustment is the center frequency. After years
of operation, all crystals will age and change frequency slightly. The ATR8
command is used to adjust the center frequency. Like all narrow-band radios,
semi-annual checks and adjustment of frequency is recommended.
14.2. Calibration Commands
The following AT commands are used to calibrate the M8. Do not ever change
these unless you have been factory trained to do so.
AT
Command
Command Description
Parameters
Factory
Default
R0
Symbol Peak Deviation
– Set the peak FM deviation of
the transmit symbols. Note: This can be a negative
number to invert the modulation.
Range: -1000 – 1000
120**
R1
Select CD pin output signal
– CD pin may be RF
carrier detect, or modem data detect, off, on, or RX data
framing, or on-line status. Line status mode asserts CD
when on-line in normal modem operation and it negates
CD when in the command mode.
Range : 0 - 5
5 = RX data framing. Assert
when outputting data
4 = Line stat.
3 = Always negate CD
2 = Always assert CD
1 = Data CD
0 = RF CD
0
(RF Carrier)
R2
Over-The-Air bit rate
- This is the data rate the radio
uses to send data over the air.
All RF modems in the
network must use the same over-the-air baud rate
.
Range:
0 = 800
5 = 9600 2L
1 = 1200
6 = 19200 4L
2 = 2400
7 = 5142 2L
3 = 4800
8 = 9600 4L
4 = 8000 4L 9 = 2000 2L
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