User Manual

PROGRAMMING

3-10

Part No. 001-3422-003

3.4 TRANSMIT TO RECEIVE SEQUENCE

1. Unkey the transmitter by bringing the 7.5 TX low.

2. Allow 3 ms for “ramp-down”

after the 7.5 TX is brought low.

3. Apply a logic high to the RX Enable line.

4. Load the synthesizer receive frequency. The SYNTH Enable line should be held high for 3 ms on the last word

to place the synthesizer in speedup mode for faster lock times. The SYNTH Enable line should then be returned

to logic low.

5. After the A0-Word is strobed in, the synthesizer will initiate frequency acquisition. The Lock Detect line (J201,

pin 7) should be monitored and in a lock (logic high) state before valid receive operation.

A “ramp-up/-down” circuit should be employed on the Loader to minimize adjacent channel interference

caused by the spectral spreading that occurs when a transmitter is suddenly switched on or off. The ramped voltage

is applied to the 7.5 TX line (J201, pin 3). The ramp should be approximately 3 ms.