air-wound inductor Q

On a sunny day (Fri, 12 May 2017 19:55:39 -0400) it happened snipped-for-privacy@notreal.com wrote in :

At the very least they will have to dispose of it (remove the plastic wrapper), or re-label it.

Yep, I muffed the back-of-envelope calculation. Somehow. That Q is measured at 40 MHz, so the performance at 1 MHz will be somewhat better. I've not looked into RF much, so the capacitor resistance contribution is another mystery to me.

On a sunny day (Sat, 13 May 2017 01:16:16 -0700 (PDT)) it happened whit3rd wrote in :

You could also increase Q by adding a tunnel-diode (Esaki diode) to cancel part of RL.

On a sunny day (10 May 2017 16:48:19 -0700) it happened Winfield Hill wrote in :

There may be an other problem at those frequencies, it is in the AM radio band.

I remember a long time ago (sixties), we got an acceptance test of a power supply design I made, and the guy was testing for ripple current... Too high! Oops, scope, what is that? AM local radio station on the wire! He was testing with those large wounded power resistors as load, tuned just right. Potcores are closed, maybe it is no issue, but we had one station 1/2 MW,

You can find a good high Q coil in that frequency range by buying a ferrite rod antenna with coil, like this for example;

No, they'll just throw it in the can. No skin off their nose. They're being paid the same.

That's why we've moved all of our new power supplies designs to above

I don't know where Mike's 3.23 ohms ESR came from. There are plenty of caps that are *much* better than that. The coil is typically the limiting factor in the Q of most resonant circuits.

I'm sure there are, I picked a ceramic disc cap from a package labeled Jameco.

I just wired 7 polystyrene caps together to get 0.05uf and got an ESR of 0.03 ohms, a huge difference. The Q of the polystyrene stack was almost 1000. Highest frequency I can test is 100kHz. I'm using a DE-5000, >

My experience is limited to resonant circuits with less than 1000pf of capacitance. So, yes it is typically the coil that limits Q.

See the last page,

Mikek

Mike, please understand that just any old ceramic capacitor does not necessarily have a high Q (low D). You need to use an NP0 (C0G).

Ok, so at 1MHz, the cap reactance is 1/10 of that and, assuming your ESR does not change, then the Q will drop to about 100. Yes?

There was a recent paper on FEM of microwave ovens. Cavity Q for stainless steel was a bit below 10,000.

On a sunny day (Sat, 13 May 2017 11:16:14 -0400) it happened snipped-for-privacy@notreal.com wrote in :

Yea, but it was not my design's fault, had him disconnect his wirewound load resistors from my supply, and guess what: the signal at 1007 kHz was even much stronger :-) The output caps shorted it, but his test leads were long enough..

supply ------------- scope | [ ] wire wounds | ///

Relief! You could even see that station with just a 10x probe in the air.

I remember as a kid I used to listen to it at secretly night with a crystal radio connected to the iron bed spiral mattress as antenna.

I picked what I have in stock. I expected it to be better than it was. It was approximately the same as the 10uf electrolytic. Poor. Mikek

That makes sense. I really like this DE-5000 meter. it checks L, C and R. also D, Q, and ESR. It will test at 100Hz, 120Hz, 1kHz, 10kHz and 100Khz. The 100kHz is a bit limiting for RF guys. Here's a function I haven't used yet, but it shows accuracy.

For some reason my computer adds &t=273 to the end of that link and it wants to jump to the next video. Either delete it or back page and hit the replay icon.

Mikek

I had the same situation at a repair shop in Lansing Mi. I would pick up the local 1320 kHz radio station with just a probe in the air. Mikek

Sounds like winding my own air-core inductor filters would be nasty, litz wire and SRF parasitics and all.

A 1 MHz sinewave gen could feed this brickwall lowpass

into my DUT amplifier and then, magically, they also have a 1 MHz, 100 ohm differential notch filter

for the output/analyzer side. 40 or 50 dB notch should be enough that a spectrum analyzer or good scope FFT can take over.

So the issue is whether the combo can give me, say, a -100 dB THD floor. The notch filter seems to use three slug-tuned inductors.

These filters are radically better than the MiniCircuits parts.

Superconductive cavities get close to 1e9. It doesn't take a lot of microwave power to create gigantic electric fields inside, enough to tear the metal apart.

On a sunny day (Sun, 14 May 2017 10:00:07 -0700) it happened John Larkin wrote in :

I have one, but it is in the GSM band: