User's Manual

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.