User's Manual

Company Confidential 59 Raveon Technologies
3. Adjust the deviation register setting so that the frequency deviation is
correct. The deviation is set with a digital adjustment. Use the ATR0
command to read or set the deviation level.
12.4 TX Modulation Balance
(Note: This step is not performed on radios with Radio Type 5)
1. Set-up a service monitor to monitor the FM deviation of the transmitted
signal on an oscilloscope. The frequency response of the demodulated
FM signal must be greater than 10Hz to 5kHz without any de-emphasis.
2. Transmit random data with the M7-UC, using the ATDT 1 command. This
command will cause the M7-UC to automatically key up, and send random
data for one minute.
3. Verify the DC center of the demodulated data is stable. The random data
should be randomly timed 1s and 0s, and have little to no AC component
on them. See pictures below for details.
4. If necessary, change the ATR9 setting so that the long data bit have the
same amplitude and DC value as the shorter ones.
12.5 RX Carrier Detect
The DCD signal from the modem may be generated by detection of RF, using an
internal signal called RSSI (Receive Signal Strength Indication). The RSSI signal
is an analog signal representing the strength of the RF carrier. It is compared
with a pre-set value, and if it is above this value, Carrier Detect is asserted. The
pre-set value may be change with the ATRA command.
When the modem is used in the Streaming Mode (non-packetized operation, you
may wish to configure the modem to require RF carrier detect to be active for the
modem to receive data. Use the ATRF command to enable/disable this feature.
To set the RF carrier detect level, perform the following steps:
1. Generate a test signal, 1kHz tone, 1.5kHz deviation, on the receive
frequency. Connect the signal generator to the antenna input. Turn the RF
level off.
2. Watch the RSSI DAC value by issuing the AT$5 command. The current
reading will be sent out the serial port.
3. Adjust the RF level to a point where you would like the RSSI to trigger the CD
signal. This is factory-set to -110dBm.
4. Send the ATRA nnn command. Set nnn to be equal to the RSSI setting you
would like the CD signal to trip at. The BUSY LED will also indicate an RF
carrier when the RF carrier is above the threshold set with the ATRA
command.