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PLL Module

2018-01-22 06:43  
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PLL Module


PLL Module


This schematic originally comes from a Dutch magazine called Free Radio Magazine in the mid eighties. It's just a PLL nothing more, nothing less. The resistor named R can be replaced by a 50 Ohm type if the power supply is 5 Volts. The dividing ratio can be programed with IC2. For the ratios see table 1. Example: If the input signal has a frequency of 10MHz, the crystal frequency output is 10.240-10.000=0.24. Now looking at table 1, we see we can make 24 by combining the 8 and 16 program switches (pin 11 and pin 12 closed to Vcc).

By trimming coil T the output will lock to 10MHz. To use this PLL in the 3 meter band (100MHz), divide the oscillator frequency by 10. Next feed this signal to pin 4 from IC1 by a 8pF capacitor. The adjust voltage coming from IC2 pin 5 should be connected to the oscillator's varicap by a 4k7 resistor. As described here, the PLL will make frequency stepping of 10kHz, to change it to 5kHz apply around minus 9V to pin 4 from IC2. When using this PLL in the 3 meter band, this will result in stepping of 50kHz instead of 100kHz.

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