Specifications

2.3 Link Budget Consideration: A link budget for the Redline radio was considered for the
distance of 20 miles. The system was considered with 28dBi panel antennas and a transmit
power of 20dBm. The free space path loss of a 5.8GHz signal at a distance of 20 miles is
calculated by the equation PL =
()
()()
22
2
4 d π
λ
=138 db. The receive power is then 20+28+28-138 =
-62dbm. The receive sensitivity of the AN-50 is specified as being –86dbm, therefore the link
margin is 24db. This margin is necessary to account for other losses not considered in the ideal
case calculated above. Losses can be occurred in the antenna cable connecting the transceiver to
the antenna, as well as pointing losses due to the antennas not being exactly aligned with each
other. The link margin is also a buffer against seasonal impairments that may occur such as
heavy rain and seasonal foliage obstruction.
For the Redline equipment it is important to note that the received sensitivity of –86dbm is the
received power necessary to complete a BPSK link. To achieve the higher order modulations a
larger received signal strength is required. This is tested and the experimental results are shown
in Figures 5.2 and 5.3. If a higher order modulation is desired to achieve a higher throughput
refer to those graphs to infer the received signal power necessary and use that as the receiver
sensitivity was used above.
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