User's Manual

Spread Spectrum Wireless Data Transceiver User Manual
LUM0002AF Rev E Version 6.3 37
The following table defines the Maximum packet size in bytes by way of charting the Min Packet Size
setting versus the Max Packet Size setting where the RF Data Rate is set to 3. Using the default settings,
the actual maximum packet size, in bytes, is 172.
Maximum Packet Size Definition with RF Date Rate of 3
Max Setting
Min Setting 0 1 2 3 4 5 6 7 8 9
0
8 24 40 56 72 88 104 120 136 152
1
12 28 44 60 76 92 108 124 140 156
2
16 32 48 64 80 96 112 128 144 160
3
20 36 52 68 84 100 116 132 148 164
4
24 40 56 72 88 104 120 136 152 168
5
28 44 60 76 92 108 124 140 156 172
6
32 48 64 80 96 112 128 144 160 176
7
36 52 68 84 100 116 132 148 164 180
8
40 56 72 88 104 120 136 152 168 184
9
44 60 76 92 108 124 140 156 172 188
Referencing the default settings, the Master will transmit up to 172 bytes on every hop. If fewer than 172
bytes are transmitted, the balance is allocated to the Slave's transmission, plus the quantity in the Min
Packet Size Setting.
For example, if a Master transmits 100 bytes, the Slave will then have a total of 116 bytes available
(72(“leftover bytes”) + 44 (Min packet size)).
(3)
XMIT RATE
Two settings for the Transmit Rate parameter are available. The setting for normal operation of the
transceiver is a Transmit Rate 1. Transmit Rate 0 is useful to qualitatively gauge signal strength in Point
to Point mode. When set to Transmit Rate 0, the transceivers will transmit back and forth continuously
regardless if they have any actual data. In Point-to-Point operation, Transmit Rate 0 should be used only
as a diagnostic tool and not for normal operation. The strength of the signal may be gauged by the Clear
to Send LED. A solid red CTS LED indicates a strong signal; a blinking CTS LED indicates a weaker
signal.
(4)
RF DATA RATE
FreeWave transceivers have two settings for the RF Data Rate (2, 3). RF Data Rate should not be
confused with the serial port Baud Rate. Setting 2 should be used when the transceivers are close
together and data throughput needs to be optimized. Setting 2 must also be used when the full
throughput of 115.2KBaud is necessary. Setting 3 should be used when the transceivers are farther away
and a solid data link is preferred over data throughput.
Note: In MultiPoint networks, the RF Data Rate must be set identically in all transceivers. Any
transceiver with an RF Data Rate different from the Master will not establish a link.
In Point to Point networks the Master’s settings take precedence over the Slave.
(5)
RF XMIT POWER
For more information, refer to the Installation Guides for the 900 MHz and 2.4 GHz wireless modems.