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El
A13
10 MHz FREQUENCY
STANDARD
INPUT
Figure 5-4. Generate Mode Block Diagram
5-27. The Frequency Standard module (A13) contains a 10 MHz standard oscillator with buffering and
switching to provide a 10 MHz signal to the EXTERNAL 10 MHz OUTPUT and to the RF Synthesizer (A5). A
provision is made for the application of an EXTERNAL 10 MHz INPUT which causes the internal standard to
shutdown and the EXTERNAL 10MHz INPUT to be switched to the EXTERNAL 10 MHz OUT and to the RF
Synthesizer.
5-28, The 10 MHz standard input to the RF synthesizer is digitally divided down to provide SYSTEM REFF
FREQUENCIES for the frequency counter, the zero beat detector, the second local oscillator in the receiver,
and the processor timing reference. Additionally reference frequencies are provided for a fixed 550 MHz
locked loop and for a programmable 500 MHz-1000 MHz locked loop. The programming of the 500 MHz-1000
MHz locked loop is provided by the RF CONTROL BUS from the processor. The SELECT SWITCH selects one
of three possible output points for the SYNTH RF output signal. The first is from the 500 MHz-1000 MHz loop
directly. The second is from a divide by two on the output of the 500 MHz-1000 MHz loop which gives
frequencies from 250 MHz to 500 MHz. For outputs below 250 MHz, the output of the 500 MHz-1000 MHz loop
is mixed with the fixed 550 MHz signal and the difference signal used for the output. For this output the
processor programs the 500 MHz-1000 MHz loop for frequencies between 550.01 MHz and 800 MHz to obtain
outputs from 10 kHz to 250 MHz respectively.
5-29. FM and SWEEP Modulation is implemented within the 500 MHz-1000 MHz loop. FM capability is 200
kHz peak which when divided by two gives the 100 kHz peak requirement. Similarly the sweep capability is 10
MHz peak which provides the 5 MHz requirement for the sweep generator and spectrum analyzer
requirements.
5-10
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