Re: Crystal Radio Tuning Capacitor
- From: ehsjr <ehsjr@xxxxxxxxxxxxxxxx>
- Date: Fri, 14 Dec 2007 07:02:55 GMT
Peter Bennett wrote:
On Thu, 13 Dec 2007 06:08:45 GMT, ehsjr <ehsjr@xxxxxxxxxxxxxxxx>
wrote:
Dave.H wrote:
I'm planning to build a crystal radio similar to the one linked to at
the bottom of this post, but the specs call for a 30-160 pf tuning
capacitor, all I can find is a 60-160 pf cap. Will this still work?
Yes, with a narrower tuning range. But you can add
switched fixed value capacitors to extend the range,
if you want. This is a kludgy arrangement, but will
get you the full tuning range:
S1 S2
--------+-----o o---+---o o---+
| \ | \ |
[C1] [C2] [C3]
| | |
--------+------------+----------+
Values:
C1 60-160 pf variable
C2 56 pf fixed
C3 30 pf fixed
Range(pf) S1 S2
29-41 Closed Open
36-68 Closed Closed
60-160 Open Open
When I went to school, the values of capacitors in parallel added, so
the ranges would be (bottom up, on your table) 60 - 160pF, 116 -
216pF, and 146 - 246pF.
Yup, me too. I drew it wrong. The intent was to have
the variable cap switched in series with the C2 & C3
combination, where C2 & C3 are switched in parallel.
Like this:
S1 S2
+-----o o---+---o o---+
| \ | \ |
[C1] o [C2] [C3]
| | | |
A-------+ +----+----------+----B
The effective capacitance is across A and B
The switches are shown in the open position.
Ed
.
- References:
- Crystal Radio Tuning Capacitor
- From: Dave.H
- Re: Crystal Radio Tuning Capacitor
- From: ehsjr
- Re: Crystal Radio Tuning Capacitor
- From: Peter Bennett
- Crystal Radio Tuning Capacitor
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