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Re: Nouveau Retro Linear Amp Designs

 

Tom WB6B

Several years ago I embarked on studying the possibility of making DIY
capacitors of the fixed and variable type.? This is where I became familiar
with making a standard size plate capacitor that could be used to determine
capacitance, and from that the dielectric factor of various readily available
materials.? The on-line tables will get you close, but for junk-box dielectrics
I found that I really needed to make reference capacitors to calibrate how
much capacitance to expect from a 2 inch by 2 inch set of plates and various
dielectric materials.?

Variable capacitors can be made with ball bearings, but shafts with
cove-shaped metal-to-metal bearing surfaces seem to be quieter and will
hold their position better than the ball bearing type.? The shafts can be
spring-loaded to keep them centered.

With today's CNC mills and 3D printing it should be possible to turn out
price-competitive RF capacitors relatively quickly.? Might even be a good
side-business for someone much younger than me.? This assumes that
the younger generation keeps ham radio alive and has at least as much
curiosity as us old timers did in our younger years.

Arv? K7HKL
_._



On Sun, Aug 15, 2021 at 4:02 PM Tom, wb6b <wb6b@...> wrote:
On Sun, Aug 15, 2021 at 09:55 AM, Arv Evans wrote:
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Hi Art,

Those are very good dielectric constant resources, thanks.

In poking around some more after checking out your links, I finally found a couple of tables with loss measurements of a limited number dielectric materials.

Seems the preferred measurement is called "Loss Tangent". The value it seems, only needs to reach a remarkably small number to become an issue.




Here is a short little summary article about capacitors, ESR, Loss Tangent and Q factor.?


Seems capacitors, when you look closer at them, have almost as much intrigue?as inductors with additional factors that pile on to the "ideal" depiction to change their actual performance. At least capacitors, in most cases, can be categorized into broad types that work best in various conditions. Always seems to be a more tenuous?balancing act with inductors.?

And just for fun, this table shows, oddly, that unsalted butter is lossier than salted butter.


Tom, wb6b
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