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Source 1/4" shaft tuning caps

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.

Reply to
Tim Shoppa
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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

Reply to
Mike Monett

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

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Reply to
Spehro Pefhany

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.

Reply to
Ken Moffett

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

Leon

Reply to
Leon Heller

How about the voltage and frequncy range ?

Rene

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Reply to
Rene Tschaggelar

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

Reply to
John Mathews

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