Ramsey Electronics URC1 Instruction Manual download pdf (Page 12)

WSR-1A• 12

 15. Install C26, a .001uF ceramic capacitor (marked .001, 1n, or 102).

 16. Install R15, a 1K ohm resistor (brown-black-red).

 17. Install R13, a 100K ohm resistor (brown-black-yellow).

 18. Install D1, a BB505 varactor diode (orange glass body with printed

characters marking the part number). This varactor diode allows the phase

locked loop to operate by adjusting the reverse bias voltage on this diode.

This diode is the capacitive part of the local oscillator, and L8 is the

inductive part. As the reverse bias voltage across this diode increases, the

capacitance decreases, therefore the local oscillator’s frequency increases.

This circuit combined with a frequency to voltage converter (phase

detector) are the major components of the phase locked loop. Be sure to

mount this part in the correct direction. The cathode, or the striped end

should be in the same orientation as in the parts layout diagram.

 19. Install C25, a .01uF ceramic capacitor (marked 103, .01, or 10n).

 20. Install Q8, a 2SC2498 NPN RF transistor. This transistor has very good

characteristics all the way up to 1GHz and more. With low noise and high

gain as part of its repertoire, this part can almost put a GaAsFET to shame.

This transistor amplifies and isolates the VCO output from the PLL chip. Be

sure to mount the flat side in the same orientation as in the parts layout

diagram. Also check that it is not a 2N3904 transistor since the pin outs and

characteristics are not the same!

 21. Install R41, a 47K ohm resistor (yellow-violet-orange).

 22. Install C39, a .001uF ceramic capacitor (marked .001, or 102).

 23. Install R40, a 1K ohm resistor (brown-black-red).

 24. Install C36, another .001uF ceramic capacitor (marked .001, or 102).

 25. Install R20, a 10K ohm resistor (brown-black-orange). Note this is a lay-

down resistor, and be sure to use the correct holes.

 26. Install C43, a 35pF trimmer capacitor (orange top, silver adjustment).

This part will allow us to get the 10.24MHz crystal running at exactly the

frequency we desire.

 27. Install R25, a 1M ohm resistor (brown-black-green).

Most of the parts we are installing right now are parts associated with the phase

locked loop. The next few parts will be associated with D1, the varactor diode.

This will make up the VCO, or voltage controlled oscillator, which will be

precisely controlled by the PLL chip.

 28. Install C37, a .001uF ceramic capacitor (marked .001, or 102).

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Ramsey Electronics URC1 Instruction Manual Page 12