TP9100 Service Manual Circuit Descriptions 59
© Tait Electronics Limited May 2005
Speed-up
Techniques
To reduce the change-over time between transmit and receive, part-time
speed-up techniques have been implemented. Speed-up involves changing
some resistor values while simultaneously changing the PLL IC settings.
This process is implemented in hardware under software control in
conjunction with use of the synthesized reference input. The result is a
transmit-receive settling time of less than 4.5ms. (The switching time is
measured for a frequency change equal to the first IF plus 10MHz or 1MHz,
depending on the repeater offsets used for the band. This implies a
synthesizer transmit-receive change-over plus an offset of 1MHz or 10MHz
in less than 4.5ms. The ramp-up and ramp-down of the transmitter further
extends this change-over time from 5.7ms (high power) to 6.3ms (low
power).
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