M7 GX Technical Manual
29
Raveon Technologies Corp.
to 450.100MHz. Alternately, you may enter the frequency in hertz by entering
ATFX 450100000
. You must enter all of the zeros if you enter the frequency in
hertz.
3. Review the frequency setting with the
ATFT
,
ATFR
, or
ATFX
command. To
see a list of all of the channels , enter
ATF
.
4. To change the radio channel, use the
ATHP
x
command while the modem is in
the command mode.
5.
For MURS versions of this product, the ATFX command will not change
frequency. See application note AN115 for more MURS band operational
information. The five MURS authorized frequencies (FCC part 47 CFR 95.632)
and associated channel emission bandwidths (47 CFR 95.633) are:
1
151.820 MHz
(11.25 KHz bandwidth) Default OTA baud: 4800
2 151.880 MHz
(11.25 KHz bandwidth) Default OTA baud: 4800
3 151.940 MHz
(11.25 KHz bandwidth) Default OTA baud: 4800
4 154.570 MHz
(20 KHz bandwidth) Default OTA baud: 9600
5 154.600 MHz
(20 KHz bandwidth) Default OTA baud: 9600
7.3. Data Transmission
To transmit data, send one or more bytes of data into the serial port of the modem.
When a full packet of data has been collected into the internal buffer of the modem,
or when there is a pause in the data, the modem will automatically key its
transmitter, and send the data over the air.
Serial Port Baud Rate
While the modem is transmitting, the user may continue to send more data into the
M6.
Because the buffers in the M6 are full-duplex, the serial port data rate and the
over-the-air data rates are independent. The serial port baud-rates may be set
slow to accommodate legacy equipment, or set at high-speed to minimize latency.
The over-the-air data rate us usually 4800 baud for narrow-band channels, and
9600 baud for wide-band, although faster or slower rates may be used.
In Packet Mode, selection of the serial port baud-rate is important. As shown
above, if the serial port baud-rate is the same as the over-the-air baud rate and the
packets are short, the channel utilization is only about 50%. But, if the serial port
baud rate is set much higher, say 2-8X the over-the air rate, the channel utilization
becomes near 100%.
Because the M6 can handle serial-port data rate far in excess of the over-the-air
rate, the efficiency of the M6 in Packet Mode is approximately the same as other
brand modems that cannot operate in a Packet Mode
— with the added benefit or
ARQ, error-free data, and addressing.
Busy-Channel Lock Out
If your system operation require the M6 modem to monitor-before-transmit, of if you
do not want the M6 to transmit on a channel that is busy, yo
u can enable “Busy-
