RV-M50-E Technical Manual
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FCC regulations require that the M50 not allow certain modes of operation. If the radio is placed in a
non-compliant configuration, this will be indicated upon entering Command Mode or when issuing the
SHOW command.
4.2.
Channel Center Frequency
Channel frequency is set with ATFX <frequency>, where <frequency> is expressed in MHz, e.g. 915.5. In
North America, channel center frequency may be set between 902.5 - 927.8MHz for 125kHz channels
and between 902.7 - 927.5MHz for 500kHz channels.
4.3.
Channel Bandwidth and Transmit Power
Channel bandwidth is set with ATBW <bandwidth>, where <bandwidth> is set according to the table
below:
To comply with FCC regulations, the RV-M50 in pier-to-pier mode uses 500kHz channel bandwidth.
Direct Sequence Spread Spectrum (DSSS) they call Chirp Spread Spectrum (CSS). Each bit is spread by a
chipping factor. The number of chips per bit is called the spread factor.
Channel Data Rate
Channel data rate varies by spreading factor, spreading factor can be set with ATSF <val>, where <val> is
set according to the table below: For the SCFHSS 500kHz channels, the settings are:
ATSF
Setting
Bit Rate for
500kHz
Channels
Duration for 20 Data Bytes
Dur. 100 Bytes
Typical Packet
FEC=0(4/4)
FEC=1(4/5)
FEC=4(4/8)
FEC=1(4/5)
7
21.87 kbps
20mS
25mS
30mS
52mS
8
12.50 kbps
44mS
44mS
56mS
92mS
9
7.03 kbps
64mS
78mS
100mS
160mS
10
3.90 kbps
125mS
144mS
184mS
310mS
11
2.14 kbps
240mS
265mS
340mS
580mS
12
1.17 kbps
480mS
520mS
680mS
(Don’t Use)
1020mS
(do not use)
Note that adjusting ATSF will affect maximum allowable packet size. For packets greater than 10-20
bytes, we recommend not to use Forward Error Correction FEC 4(4/8) with the Spreading Factor ATSF of
12, because packets are too long for the system.
Channel Occupancy
Regardless of the number of channels employed, a channel may not be used for longer than 400mS in a
period of 400mS * channel count, to comply with FCC 15.247(f). The modem automatically enforces this,
and may temporarily delay a transmission to comply as needed.
ATBW Setting Channel Bandwidth
125
125kHz
250
250kHz
500
500kHz
