coil impedance

But it would block air flow. Tradeoff.

Skin effect dominates. I smoked several commercial inductors that were operating well within their current ratings.

This thing makes kilovolt pulses, about 7 ns wide, at up to 4 MHz. That usually takes a rackmount box full of power supplies and mosfets and heat sinks.

I figure that I need fat wire. Lots of surface area helps keep the skin resistance down and helps cooling. Spacing the turns reduces proximity effect and lets air in. Litz might work too.

Apologies to anyone who doesn't approve.

John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics

I wasn't desperate, it was fun.

It speeds things up and handles mixed units. Do you still use pencil and paper and a slide rule?

Of course I had requrements. It's a cavity dumper of sorts.

Design a better kilovolt pulser. Show us.

My main object is to amuse myself. Often enough, people want to buy the results.

John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics

I used it for a shortwave preselector with Siemens K1 pot cores. Q > 400, avoid to put copper near the air gap. (eddy currents)

Gerhard

In fact it is you that is talking nonsense. For a company to make a reputation for building good RF inductors, they merely have to make them better than the competition. To do it "very well" they'd have needed some kind of mathematical insight into what they were doing, and there wasn't a lot of that around in UK industry when I was working there from

Look at the range of chapter headings in "Modern Ferrite Technology". I find out about stuff I've worked on. I know very little about many of the subject areas covered. That sort of book is usually some academic lecturer's course, built on a presentation which eventually worked for the students exposed to it - "Art of Electronics" was created for a Harvard electronics course. Writing a book is a heroic effort - my wife did it for her specialist subject and it took a huge amount of work, but she had given a lot of talks and lectures which she could - and did = draw on.

It should. Wasting people's time by presenting incoherent data should be a criminal offense. Of course self-preservation should prevent you from agreeing with that conclusion.

It isn't. But the fact that you can't recall that detail is revealing.

It was even worse when they didn't go pop. It once took us a day at EMI Central Research to find out why our prototype phased array ultrasound machine wasn't focussing, and it turned out to be a wrongly mounted tantalum bead capacitor messing up a rail voltage in the hyperbolic function generator. That was a day when we were supposed to be showing off the machine. I can't complain - I got to put together a second version of the protoytpe with everything on printed circuit cards, which was reliable enough for us to ship around the UK as a clinical trials machine. One of the printed circuit boards was a bit too tightly packed

- I'd wanted to split it into two but my boss was correctly convinced that we could squeeze it all onto one board, but it did take a lot of tedious fiddling with the layout. Laying out two boards would have been cheaper - we had to pay for all that tedious fiddling.

Show us the specification you were designing to. And throw in the money you got for doing the job. The specification was probably inadequate - customers do have a nasty habit of finding new requirements after you have roughed out a tentative solution.

You may believe that. More objective observers might be more skeptical.

No Bill. I wasn't talking at all. I merely quoted the words of others.

The fact that you haven't quoted the post where this detail was mentioned is also revealing. Either do so or shut up.

Selective quotation is a very effective way of creating nonsense messages. You may not even be aware that that is what you are doing.

The quotes are exact quotes in the order which they were said. Nothing was created by myself, it was only replicated correctly.

What I actually posted was

"In fact it is you that is talking nonsense. For a company to make a reputation for building good RF inductors, they merely have to make them better than the competition. To do it "very well" they'd have needed some kind of mathematical insight into what they were doing, and there wasn't a lot of that around in UK industry when I was working there from

You snipped out the bulk of the comment without marking the snip, which made my response look very different.

But if you left out bits between the exact quotes you can still covey a misleading message. That's what selective quotation means.

You've just provided a prize example of it here

Unfortunately for you, your paragraph above was posted AFTER the quotes in question.

Even if relevant (which it isn't) I did not snip out any of your paragraph which begins "In fact" and ends with "nor flexible".

My reply came after your first sentence, but none of your text was snipped or changed at all.

If you still think I snipped out the bulk of an irrelevant comment of yours then please cite exactly the post and the line where this happened. Give the date and exact time of the post.

If you can't do that then stronger words than shut up are coming.

Obfuscating the truth is what should be a criminal offence.

Unfortunately for you I did not leave out bits between the exact quotes. Therefore nothing misleading is being conveyed by myself either intentionally or unintentionally.

Here is the quote in the exact context with nothing whatsoever changed or snipped:

">>>> I worked for a company that built its reputation on the R.F. inductors

You've just provided a prize example of your stupidity Bill. You may not even be aware that this what you are doing.

DT banned him from Mar-a-Lago after he messed with some of DT's young female employees.

DT's taste in women trends towards the bigger end.

John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics

You can Spice -150 dB as a parlor game, but you'll never build anything that good. Opamps won't do it. Thermals won't allow it. Not even real capacitors or resistors.

And how would you demonstrate it?

John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics

Yes. You posted your response after the bit you wanted to respond to, so you were responding to that rather than what I was actually saying.

This is the problem with selective quotation, and you have just established that you are too stupid to realise this.

Except that posting your text where you did changed the message you were responding to.

That's what Donald Trump now claims

Grabbing them by the pussy?

JM claims to have done. Jim Williams seem to have got better than -120dB on the bench with FET gain control Thermal effects are slow and won't generate harmonics. Low temperature coefficient resistors don't generate much in the way of harmonics. You'd have to be picky about your capacitors. Some plastic film capacitors don't present much of a problem with charge soak and other non-linear effects.

I'd go for polypropylene film parts. One of the engineers I'd worked with had used Teflon film capacitors in a project where this was a problem - he talked about in his job interview with me, and it did convince me that we ought to hire him. I wasn't the only interviewer who liked him and he did perform remarkably well after we'd hired him.

Some op amps are remarkably good - Jim Williams made that point decades ago.

Run a Fourier transformer on the sine wave generated and look for the harmonics? Build a high Q filter for the frequency you are generating and amplify the stuff that gets through it? Check out the Jim Williams application notes that talked about the subject.

Teflon has phase changes at 19 and 30 deg C which make it very hard to get stable performance over temperature. This also affects coaxial cables in high precision applications. John