Home made 5 pf trimmer capacitor

Thread Starter

joemayer

Joined May 26, 2013
2
I am in need of a 5 pf trimmer cap and was thinking whether it would be possible to make one from small washers and mica?
 

Thread Starter

joemayer

Joined May 26, 2013
2
Thank for responding guys. I need the 5 pf trimmer to offset the vfo of my QRP cw transceiver about 1 kHz below the transmit frequency on receive, I wonder if the twisted hookup wire will do the job?
 
Last edited:

crutschow

Joined Mar 14, 2008
29,487
Thank for responding guys. I need the 5 pf trimmer to offset the vfo of my QRP cw transceiver about 1 kHz below the transmit frequency on receive, I wonder if the twisted hookup wire will do the job?
We've given you the info. I suggest you give it a try and let us know if it works. You shorten it and change the twist to tweak the value. Start with a longer wire then you think you need and keep snipping off a short piece of the ends until you get the right value.
 

atferrari

Joined Jan 6, 2004
4,576
We've given you the info. I suggest you give it a try and let us know if it works. You shorten it and change the twist to tweak the value. Start with a longer wire then you think you need and keep snipping off a short piece of the ends until you get the right value.
Few weeks ago I did that with a pair of tightly twisted wires.

If I recall right, 8 cm measured 8pF. After pruning it little by little I found the relationship to stay quite consistent down to the last 2 cm.

I wonder how stable the actual value could be. Besides temperature, what else could ruin the value?
 

GopherT

Joined Nov 23, 2012
8,012
I personally think it would be easier to buy one
Unfortunately, the OP doesn't know exactly what value he needs but is likely somewhere near 5pF and the wants to adjust/ tune his circuit. The lowest value is 3.5pF and, after soldering, may be outside the range the OP needs. The twisted pair method can be used for very fine tuning. Wires with varying thickness insulation can be used for varying degrees of control.
 

edwardholmes91

Joined Feb 25, 2013
210
Unfortunately, the OP doesn't know exactly what value he needs but is likely somewhere near 5pF and the wants to adjust/ tune his circuit. The lowest value is 3.5pF and, after soldering, may be outside the range the OP needs. The twisted pair method can be used for very fine tuning. Wires with varying thickness insulation can be used for varying degrees of control.
Fair do's, the link I posted though had ones down to 1.5pF ;)
 
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