Source 1/4" shaft tuning caps

May 11, 2005 6 Replies
T

For linear tuning "linear in capacitance" isn't the right choice. (If the variable C is a tiny fraction of total tank C then it's not too bad of an approximation.)

The 365pF capacitor from

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is about as ubiquitous as you're gonna get. Finding old AM radios at garage sales worked when I was a kid but I don't see them nearly as much anymore.

There used to be rules-of-thumb in the ARRL handbook about filing common capacitors to give linear tuning. To some extent they are reconfigurable as well (changing number of plates by removing sections.)

Tim.

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M

How about the miniature tuning caps used in AM/FM radios? Made in bazillions per year, reasonably stable and cheap. Trim caps are included.

An inexpensive coupler could extend the shaft as needed.

Mike Monett

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S

These guys in the UK seem to still be making them, at least in small quantity, however the shaft diameter is "6.35mm". ;-)

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They used to be Jackson Brothers. I just scanned the last PDF page of their history. A sad story of a company at the trailing edge.

Best regards, Spehro Pefhany

"it\'s the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com
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K

John Mathews wrote in news: snipped-for-privacy@4ax.com:

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I just bought a bunch and made crystal radios with a group of kids. It's fun to see computer age kids get excited about the functionality of primitive technology.

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L

Mainline in the UK makes some of the old Jackson Bros range.

Leon

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R

How about the voltage and frequncy range ?

Rene

Ing.Buero R.Tschaggelar - http://www.ibrtses.com & commercial newsgroups - http://www.talkto.net
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J

Can anyone advise regarding a source for variable tuning caps with a



1/4" shaft? Similar to those used in "old time" radio tuners.

I would prefer single gang, half plate and linear, or the closest thing to it. And in the smallest possible physical size.



Capacitance value is not a consideration. The circuit can be made to suit.



We need an ongoing supply, so a surplus is not ideal. But is anyone still making or stocking them as a regular item?



Thanks for any suggestions.



John


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