PVC-224 Variable Capacitor and Ferrite Coil Antenna

The PVC-224 is a 224 pF variable capacitor for AM radio projects. On the front side, it has "FU" stamp marked. I just recently bought one of these for use with a crystal radio but could not find the pinout or a datasheet for it.

From what I can ascertain using my digital meter, pin 6 and pin 5 are internally connected and may be a common ground. Measuring the capacitance between the common (pins 6 or 5) and pin 2 the capacitance varies from 170 pF to 26 pF approximately. The capacitance between the common (pins 6 or 5) and pin 4 varies from 48 pF to 27 pF approximately.

The coil shown at the top of the page has a tap because I wanted to compare my 500 pF variable capacitor with the cheaper 224 pF one that I recently bought (three for two pounds). Therefore the orange section consists of 44-turns for connecting the 500 pF one, however in order to use the 224 pF variable capacitor I had to extend the coil by adding 26-more turns resulting in the addition of the orange/white section. Hence, the total number of turns required for a 224 pF capacitor is 70. The coil wire is a single copper core from CAT5e as described in the previous pages.

500 pF Open-Plate "Bad-Boy" vs. 224 pF Plastic "El-Cheapo"

I compared my open-plate 500 pF (bad-boy) variable capacitor with the feeble-looking plastic one in a simple crystal radio circuit and was surprised because the cheaper feeble looking one actually performs better! Hence, I shall be using it in my projects from now on.

224 pF Capacitor Pinout and Wiring

Connecting pin 2 and pin 4 together will produce a maximum capacitance of approximately 218 pF. If you can find a datasheet for it, or have more information, then please feel free to send an attachment. The only problem with this variable capacitor is that it is so small that I might have to use a block of plastic or wood to stage it upon. For the tuning dial, I decided to use a plastic yoghurt lid, because with that, all I needed to do was to make a hole in it for the shaft, and use a blob of hot-melt glue from a glue gun to secure the shaft to the lid.

This Article Continues...