User Manual

APPLIED TECHNOLOGY SOLUTIONS, INC.
Document: FCC1225manual.wpd issued: jan99 revised:(original) page: 8
These signals drive the despreader mixer which produces a BPSK at the 2
nd
IF frequency. This signal is further
amplified and filtered, prior to going to the FPGA for demodulation.
Receive AGC control for the RF and first IF amplifiers is generated from the composite IF signal
by the AGC generator. The AGC loop maintains a fixed signal level at the despreader output.
Channel switching is accomplished by changing the frequency of the local oscillator that drives
the TX up-converter mixer and the RX down-converter mixer. The output from the local oscillator is shared
between the two mixers. The state of the CHANNEL logic signal from the FPGA causes the local oscillator to
output the appropriate frequency for either Channel A or Channel B operation.
3.2 RF CHARACTERISTICS
In rural areas, the Model 1225 provides line-of-site communication range with a practical limit of
approximately 3 miles over normal terrain. Suburban communication range is affected by reflections and fading
with a 0.5 mile radius being typical. In metropolitan areas, communication ranges are dependent on the site
characteristics such as building density and RF environment. Operating ranges of approximately 1 block radius are
practical.