Radio tuning capacitor

Question

In a radio tuning capacitor that consists of semicircular plates , are the plates connected in series or in parallel ?

Each set is all assembled on the same metal shaft, so... – Jul 25 '19 at 07:43 — , Jul 25 '19 at 07:43

score 2 · Answer 1 · answered Jul 25 '19 at 00:36

2

The plates on standard Radio tuning variable Caps are in parallel

answered Jul 25 '19 at 00:36

Autistic

14,235
2
27
65

Do you have a picture of how the plates of such a capacitor are wired ? – user207332 Jul 25 '19 at 01:04
@user207332: I don't think you can really say that the plates in a tuning capacitor are "wired" in any way. One set of plates will be mounted on, and connected to a metal support, while the other set of plates are mounted on, and connected to, a metal shaft, The metal support forms one terminal of the capacitor, while the shaft is the other terminal. The photo in robert Endl's answer illustrates the typical construction. That would be considered a "trimmer capacitor" rather than a tuning capacitor, but the construction is similar. – Peter Bennett Jul 25 '19 at 01:48
I got it . thanks . – user207332 Jul 25 '19 at 02:09

score 1 · Answer 2 · answered Jul 25 '19 at 01:04

A tuning capacitor has two interleaved sets of plates, with the sets insulated from each other.

I suppose you might say the plates of each set form parallel capacitors(the plates are physically parallel).

You could consider the sets of parallel plates as representing a number of capacitors in parallel (i.e. you might consider the space between plate 1 of set A and plate 1 of set B as one capacitor, and the space between plate 1 of set B and plate 2 of set A as another capacitor), but we don't normally think of the assembly in this way.

In practice, the thing would be considered as a single variable capacitor (or more common, I think) as being two variable capacitors mounted on the same shaft. With a two-section variable capacitor, one section might tune the RF amplifier, while the other section tunes the local oscillator of a superhetrodyne receiver.

Robert Endl · Answer 3 · 2019-07-25T07:55:05.570

1

This is as good a picture as any. The plates are in parallel.

Edit: The difference between a trimmer and a tuning capacitor is in the details. A trimmer is simple and a tuning capacitor might have multiple sections, gears, ball bearings, special plate shapes to get a rotation that is linear with frequency or wavelength, or an integrated tuning capacitor for calibration.

edited Jul 25 '19 at 07:55

answered Jul 25 '19 at 01:20

Robert Endl

2,197
11
12

That's a trimming capacitor, not a tuning capacitor. Granted, the idea is similar, but it isn't really made for continuous end user adjustment – Chris Stratton Jul 25 '19 at 01:30

Radio tuning capacitor

3 Answers3