3-18pf air core capacitor

Thread Starter

AnonymousNerd

Joined Mar 5, 2010
6
Hi,
I am building this little FM transmitter:http://aaroncake.net/circuits/fmtrans.asp. It calls for a 3-18pf air core variable capacitor. I have many air core caps from FM receivers, but I do not know if they are the right value.
Does anyone know of a device that would have a suitable cap in it? Does anyone know where I could see a photo of a capacitor of that size for reference?
Thanks,
AnonymousNerd



P.S.
I attached some photos of a couple that I have.
 

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Last edited:

Thread Starter

AnonymousNerd

Joined Mar 5, 2010
6
Thanks for the response.
Today I found a smaller one that looks more like the one used on the transmitter. I attached a pic of it. Do you think it would work?
Thanks:)
 

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bertus

Joined Apr 5, 2008
22,270
Hello,

That would work also, but the foils between the plates will tear when you tune it to rough.

The ones rjenkins showed you are more rigid and can stand more power.

Bertus
 

Thread Starter

AnonymousNerd

Joined Mar 5, 2010
6
radrajith;
Yes it works, I used the smaller one and etched a PCB based on aaron's layout. It would probably work in perf-board if you used a similar layout but I am not total sure. As far as I know, it is best to make RF circuits as compact as possible.
Good luck:).
AN
 

sceadwian

Joined Jun 1, 2009
499
Remember, those things need to be tuned with a plastic screwdriver with a long bit and almost anything near them will effect their value.
 

bertus

Joined Apr 5, 2008
22,270
Hello,

Like sceadwian said; you need to turn the capacitors with a plastic or ceramic screwdriver.
There are special "tuning" screwdrivers for sale.
Most of them have two ends, one of full plastic and the other side enforced with a tiny piece of copper.

Bertus
 

radrajith

Joined Oct 2, 2010
6
i dont have the smaller tuner but i have the tuner which u showed on first message so did it work and also for the coil what did u use
 
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