Variable Capacitor Dual Gang for AM Radio Projects Screws Control Knob 65pF 145pF 210pF Total

This is one item of new, dual gang miniature tuning capacitor with a solid polyethylene dielectric as shown in the pictures. The higher pack quantity options are cheaper per item.

The short brass shaft has been extended to 18mm with a 6mm polyethylene extension which is firmly attached with a screw. The extension allows the use of standard radio knobs designed for 6mm diameter round shafts. Two M2.5 screws are included for panel mounting along with two loose nuts which allow for spacing behind thin panels. The mounting screws must not go into the body too far or the FM capacitor sections will be damaged. Using the loose nuts on a thin panel will avoid this.

The case measures 21 X 22 X 13mm. The knob provided is 24mm diameter and 20mm high. The additional height allows the knob to cover the shaft completely if mounted on a thin panel, or it can be screwed on further up the shaft if the mounting panel is thicker.

The middle connection is the common ground terminal for the two sections. The terminal next to the C3 mark is the 65pf section. The terminal next to the C4 mark is the 145pF section. You can connect the two outer connections together to make a variable capacitor of 210pF in total. The minimum capacitance of C3 is approximately 4pF. The minimum capacitance of C4 is approximately 5pF.

There are two trimmers on the back. When the C3 trimmer is fully meshed this adds about 12pF capacitance. When the C4 trimmer is fully meshed this adds about 14pF. The trimmers are used to make up stray capacitance to set up the tracking in superhet radio designs. The shaft rotation is 180 degrees.

You can use these in crystal sets, TRF, regenerative radios and receiving loops where the trimmers are best set for minimum capacitance with the plates fully un-meshed. These are not suitable for transmitting loops. The long connection terminals allow the easy use of 3A mains terminal block connectors to attach wires without soldering.