Variable Capacitor 200pF Total

Variable Capacitor
            200pF Totalelectronic
            schematic symbol for variable capacitor

This variable capacitor has two seperate variable capacitors inside which are used connected in paralell to form one single capacitor of higher value.  The middle connection strip is the common ground connection.  The two sections have maximum capacitances of 59.1 and 141.6pF and so form a total of 200pF.  The two outer strips are connected together in the terminal strip circuit.  The schematic shows a 320pF maximum type but the exact value is not important.  The smaller value will give a slightly reduced tuning range but this also depends on other factors, like the stray capacitance of the coil and circuits.

There are also two trimmer capacitors internal to this variable capacitor which are used to add a fixed amount of capacitance when used in other designs.  They need to be adjusted for minimum capacitance as shown in the pictures below.  Minimum capacitance is when the top semi-circular plate attached to the screw is moved so that the lower static plate is completely exposed.

            capacitor trimmers set to maximumVariable
            capacitor trimmers set at mid capacitanceVariable Capacitor trimmers at minimum capacitance.

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