There is an artical posted here about tubed phase shift oscilators at : -
http://www.rfcafe.com/references/pop...lectronics.htm
Its an old 1958 article with a hell of a lot of info to digest because unlike so many modern descriptions of anything technical, the old guys could say a lot, and not leave out very much. I think my father's generation were better communicators than many of today's website creators who just post a stupid brief plagerised picture of something, then think they are God's gift to the Universe of Information.
But I digress.
I do have a lot of 3 gang tuning caps from old radios which will never be used for radios again, and so its possible for me to mount maybe 8 of them in a box with so I'd get 3 caps with variable range 8 x ( 45 - 450pF ), ie, 360pF to 3,600pF.
To make a phase shift oscilator for 6 F ranges I need 6 sets of 3 R for each range, between perhaps 200ohms to 20Megohms, which isn't difficult.
I'd need 3 pole x 6 position switch for 6 F ranges, not difficult.
The paralleled tuning caps need not all be exactly the same type, or have the same C, although each gang in each cap should be the same, which all the ones I have are.
Has anyone else built a decent phase shift oscillator with wide range of F?
Patrick Turner.