kwf@ece-csc.UUCP (01/23/87)
I'm looking for a panel-mount, variable capacitor for a project I'm
working on here at home. The maximum value needs to be somewhere around
50 pF of so. Trimmers won't work because I need to put a knob on it.
I know that Sprague out of NY sells one, but they have a $100 minimum order
limit, and I only need one of them. I haven't found anyone else who
sells such a critter.
At first I tried using a standard 365 pF tuner capacitor and removing some
of the plates to reduce the capacitance, but it was rather unstable.
I would much rather have the real thing.
If any one knows where I might find one, I would appreciate some help.
Thanks for listening.
Kenneth Fernald (North Carolina State University)
kwf@ece-cscbenz@ge-rtp.UUCP (01/25/87)
In article <3201@ece-csc.UUCP>, kwf@ece-csc.UUCP (Kenneth W. Fernald) writes: > I'm looking for a panel-mount, variable capacitor for a project I'm > working on here at home. The maximum value needs to be somewhere around > 50 pF of so. > > At first I tried using a standard 365 pF tuner capacitor and removing some > of the plates to reduce the capacitance, but it was rather unstable. Putting another cap in series will reduce the overall value. 58 pf in series with 365 pf will give you 50 pf. I don't know the min cap of a tuner, but if it were, say 100 pf, you're final value would be 37 pf. Well, maybe it's not the best solution (or even a good one), but maybe you can use it. Chuck Benz - benz@ge-rtp still at GE Semiconductor RTP, NC
carl@sdcsvax.UUCP (01/26/87)
In article <3201@ece-csc.UUCP> kwf@ece-csc.UUCP (Kenneth W. Fernald) writes: >I'm looking for a panel-mount, variable capacitor for a project I'm >working on here at home. The maximum value needs to be somewhere around >50 pF of so. Trimmers won't work because I need to put a knob on it. > >At first I tried using a standard 365 pF tuner capacitor and removing some >of the plates to reduce the capacitance, but it was rather unstable. > Have you considered putting 60 pF or so in series with your standard 365 pF capacitor? Then you will go from a minimum capacitance of about 30 to a maximum of 50 pF as the variable is tuned. Oh for the junk box of my youth!! By the way, is the instability mechanical, or is neither side of the variable cap. grounded so you have also electrical instabilities? Maybe a circuit redesign could help too.
grr@cbmvax.UUCP (01/27/87)
In article <3201@ece-csc.UUCP> kwf@ece-csc.UUCP (Kenneth W. Fernald) writes: >I'm looking for a panel-mount, variable capacitor for a project I'm >working on here at home. The maximum value needs to be somewhere around >50 pF of so. Trimmers won't work because I need to put a knob on it. Try one from a junk FM radio - it should be closer to the value you need though perhaps on the low side... -- George Robbins - now working for, uucp: {ihnp4|seismo|rutgers}!cbmvax!grr but no way officially representing arpa: cbmvax!grr@seismo.css.GOV Commodore, Engineering Department fone: 215-431-9255 (only by moonlite)
ch@well.UUCP (01/27/87)
[..] Have you considered using voltage-variable capacitance diodes? (varactors) Depending on the requirements of your project, it may turn out that they will provide superior performance at a lower cost than mechan