tuning an LC

"miso"

Never post here again.

See my other post, 8:37 PM.

Cheers

Phil Hobbs

Actually, C0G is better than any film*, in tempco and ESR, and maintains rated tolerance at many times rated voltage. That's part of why they're expensive.

Only type II (high K) dielectrics suck.

Tim

"John Larkin" wrote in message news: snipped-for-privacy@4ax.com...

Is that before or after soldering? They might've aged during shipping ;-)

Tim

--you can control it electronically, using a PLL or FLL. I agree that they aren't the most stable things in the world, but neither are silicon varac tors. So what? It's inside a feedback loop. Of course, one has to maint ain enough design margin to guard against eventualities, but that's SOP.

John's particular problem. It is, however, one very cheap, simple, and pr obably effective solution. I didn't invent it, but I think it's pretty.

It's got its charms, but John particular problem rests in his delusion that he can't get an inductor better than +/-20%, and that trimmable inductors have to be small and high frequency.

Several people have pointed out that this is wrong - including me, Jim Thom pson and Phil Allison, none of whom he likes very much, so he's ignored the point.

Just to waste a bit more bandwidth repeating the information, he could buy a heavily gapped ferrite core which could offer - say - 160nH+/-3% per turn squared - and wind himself a +/-3% inductor. If he bought a heavily gapped EPCOS P26x16 pot core with a central hole, he could also buy a screw-in ad juster which offers fine control of inductance by bridging the central gap in a smoothly variable way.

It's a very old-fashioned solution, but it works really well, and has done so for years. The parts are still stocked by some broad line distributors, including Newark and Farnell. I've posted part numbers in this thread.

One of my more hilarious moments was when I was invited into a Top Secret meeting with an Admiral... who proceeded to describe his needs with a MULTI-block diagram on a chalk board (~1965 :)

After about 1/2 hour of this, I jumped up and accurately guessed what he was actually trying to do... much to his consternation that I had guessed his "secret".

I then proceeded to show how to do it with about 5% of the number of blocks.

Ever since I have always allocated enough time in my quotations to have a complete "shakedown cruise" with the customer to determine his actual needs. Makes for much smaller and much less expensive chips... that yield good!

Most of the time I get to do it my way. Occasionally I'll get an insistent customer, then I make sure they sign-off on their way of doing it. They usually end up being sorry for being insistent. (They're usually PhD's >:-} ...Jim Thompson

The objective of my inductor and capacitor is to simulate an actual inductor and capacitor. The LC *is* the load. Makes sense to me.

We check a few parts on every reel, in receiving, before we put them into stock. When we saw those 2.2uF caps being almost all out of tolerance low, we used several different c-meters; all read about the same.

Maybe some other guys could check their hi-K caps.

The "L" has no other function than to just sit there and recirculate current? No further use than amusement ?>:-} ...Jim Thompson

Yes they seem really good, krw might have been thinking of x7r?

On a sunny day (Mon, 18 Nov 2013 08:52:00 -0800) it happened John Larkin wrote in :

I had 1 uF 100 pcs ceramic caps from ebay, many were below tolerance, often a few percent.

That, and making us a ton of money.

And designating you a smug, useless smart-ass. ...Jim Thompson

I don't use them. I think I use one X6S and everything else is either C0G(small stuff) or X7R. X7R is bad enough at voltage. I don't need worse problems. I've found that high-K caps aren't worth the money spent on them.

I once designed some FPGA-based video cameras (color and a FLIR) for a military application. The frame and bit rates were classified (secret) but the number of lines and pixels per line (COTS CCDs and FPAs) and horizontal rate weren't, so I had to work with that "incomplete" information because I didn't have a clearance (and didn't want one). ;-)

The government really is as screwed up as Obamacare. Everywhere.

The best metalized polypropylene capacitors have ESRs and DA at least as good as the best C0Gs (for C>=1nF or so), maybe even better. Sorry, they're not cheap either, but possibly a better choice if C*V >? 5 V*uF.

Polyesters are the X5S's of the film world.

On a sunny day (Mon, 18 Nov 2013 12:54:25 -0500) it happened snipped-for-privacy@attt.bizz wrote in :

Like this?:

On a sunny day (Mon, 18 Nov 2013 18:00:38 +0000 (UTC)) it happened Frank Miles wrote in :

And I thought it was Mickey Mouse :-)