Electronics > Beginners
Air gap variable capacitors - buy cheap?
aneevuser:
I'm looking for a variable capacitor suitable for tuning over the AM frequency band, and this:
https://www.ebay.co.uk/itm/Single-Joint-Air-Dielectric-Variable-Capacitor-12PF-to-365pf-250M-35-29-26mm-/192610325869
at about 9 quid looks suitable. However, having looked around, I've seen similar caps priced at £80 quid or more, or similar in dollars. So I'm wondering what I'd actually be getting for the £9 price - cheap junk or something usable?
Does anyone have any knowledge of these?
bsfeechannel:
Does the fact that the product was probably made in China account for the lower price?
soldar:
Wow, those used to be so common fifty years ago but I am surprised they are even made any more. They used to make two working together in tandem, one would control the antenna tuning circuit and the other would control the local oscillator. They were extremely common and extremely cheap.
There were (and are) others which were much more expensive because they were for specialty uses like high voltage for tuning transmitting circuits, etc. but for a small one like the one pictured I think the price is right and there is no way it would sell for much more.
Also note that the AM tuning types are not linear but the rotation axis is offset.
https://en.wikipedia.org/wiki/Variable_capacitor
I guess they still find and sell new old stock
https://www.ebay.ca/itm/392248490930
https://www.ebay.ca/itm/263233681710
They can ask whatever they want for them but there no way I consider them to be worth more than 10 USD.
aneevuser:
--- Quote from: bsfeechannel on March 19, 2019, 04:46:06 pm ---Does the fact that the product was probably made in China account for the lower price?
--- End quote ---
I'm not sure. They seem to be about 10% of the price of the EU/USA versions, which seems rather low even by Chinese manufacturing standards.
Still, I think I'll take a punt and see what they're like - after all, no one lies on their deathbed wishing that they bought fewer Chinese-manufactured air gap capacitors, do they? I'm gonna live life to the max!
aneevuser:
--- Quote from: soldar on March 19, 2019, 06:17:37 pm ---Wow, those used to be so common fifty years ago but I am surprised they are even made any more. They used to make two working together in tandem, one would control the antenna tuning circuit and the other would control the local oscillator. They were extremely common and extremely cheap.
--- End quote ---
Don't I know it - I had two or three hanging around at home when I was a teenager, from disassembled valve radios, but that was about 40 years ago. I guess I dumped them at some point. Si la jeunesse savait, eh?
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