1 ohm transmission line

Yeah, z gets inverse on w, so one can push Appcad to its width limits and just scale from there. So, why does Appcad give up?

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.highlandtechnology.com  jlarkin at highlandtechnology dot com

How big a box are you picturing? At the vanderbitl FEL there was a lumped L/C 'storage' line that pulsed the Klystron. (I think it was a few us pulse.) The inductors were coiled sections of copper tubing... maybe 24 of them with adjustable taps. The thing sat in a bath tub sized oil bath. You could only tune it up at low voltage...and of course it would change in mysterious ways at full voltage. No one every let me play with it though.

George H.

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make you own?

-Lasse

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Fets are certainly an alternate way to do it, like those IR DirectFets maybe, the ones with tiny source inductances. My pulse duty cycles will be low, numbers like radar, so there won't be enough stored energy to knock over coffee cups or anything like that.

Just connecting to the (un-named) load is a big problem. At, say, 10 amps per ns, every nH adds 10 volts of drop. Which is why a relatively high impedance, high voltage, charged transmission line is interesting.

Past experience:

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That's just the Spice hack. In real life, I'd ground the line, charge it gently, and discharge at very low duty cycle. avalanche transistors, of course.

I also think the PFN and the

It's nice to have a lot of voltage to blast through connection inductances.

Duty cycles will be low, 0.1% maybe. The load could float, I think. I don't know very much about the load or about the customers application or technology. I'm in the phase of scribbling and researching, in advance of visiting some potential customers and trying to look like I know this stuff. That's actually exciting, in a weird scary way.

I wish! It will probably need to be a lot smaller, if only because of that damned speed of light thing.

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Incwww.highlandtechnology.com  jlarkin at highlandtechnology dot com

The size of, say, a Wonder Bread sandwich.

At the vanderbitl FEL there was a

Pulsed power is fun, like a big Marx or maybe NIF. I get the see them now and then, but only with power off. Bummer.

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Just considering possibilities, which led to the low-Z tranny line musings.

I've recently got interested in kapton flex lately, for other projects, and I need to learn more about it. Got any good flex fab sources to recommend, like for plated-through rigid-flex stuff?

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Ok, if it's just for sports I understand. But if under time/space/cost pressure I'd look at the brute force transistor method first. Pulse shaper lines are becoming a thing of the past unless it is an application between darn fast and super darn fast, and where cost is not important.

You could contact these guys:

Nowadays nearly any reputable PCB house does flex. But AFAIK the only method to make very long lines that way is a "rectangular snake cut" out of a large sheet and then foldovers. But be careful, for some application this is patent-protected.

You've made Trinitite!

Indeed, it looked just like in the 2nd picture:

Thanks. I learned something new today.

Indeed. How _does) skin effect affect a microstrip TL behavior?

Parallel micro-coax lines might be better.

and

Pretty much the same way as it always does. After a certain copper weight it won't make too much more sense to add weight.

Possibly. But at the power levels John is contemplating it all has to be beefy.

On Mon, 15 Apr 2013 09:02:47 -0700, John Larkin wrote: ...

free book on the subject at:

I had a need to figure out transmission line impedances; the microstrip equations on Wikipedia seemed to work well. Of course, I just needed to know what was wide enough and thin enough: I didn't need to hit a characteristic impedance exactly.

I think that the equation basically depends on a fringe-effect correction for thickness that pretty much goes away as the thickness gets -- um -- thin. At any rate, it makes both intuitive sense, and the equations come out, that for a given thickness with a small thickness to width ratio, the line impedance is pretty much inversely proportional to the width.

So if you had to fine-tune the impedance you could probably make up a couple of test samples, measure, then adjust. I doubt you'd have to do too many iterations before you were getting more impedance variation due to material and method variations than due to the actual dimensions of the metal pieces.

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If that's intended to be speaker wire, they are crazy. About the only thing speaker wire can really do badly is add inductance, and those two wide, separated conductors are about as bad as you can do.

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but they can be glued to a wall and painted over or put under a carpet some even come with adhesive backing, so the WAF is higher ;)

some also mention them for low voltage lighting, I guess for a bunch of LEDs on a ceiling it would quite well, just glue up a grid paint over and connect where you need to

-Lasse

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.highlandtechnology.com  jlarkin at highlandtechnology dot com

Wow... how many amps through this sandwich? What are the magnetic forces involved? Are things gonna flex with the current? (just asking)

George H.

In most cases I'd agree with you... the high inductance will lead to some treble rolloff. Maybe an OK tradeoff for ease of installation in cases where Spousal Approval Factor and the specifics of the room construction requires that the speaker wiring be surface-mounted but "invisible", but maybe not... I wouldn't use this approach in any but special cases.

I do recall some cases a few years (decades) ago, in which some "high-end" boutique audio power amplifiers were very sensitive to capacitive loading. Stick a long run of high-C-per-foot speaker cable on them, and they'd go unstable and start to oscillate (and might even let the magic blue smoke out). Amps like this would be quite happy with Flatwire, I think... but not if it were folded flat into a low-Z transmission line.

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Coax has high breakdown voltage, so is inherently inefficient in storing energy at lower voltages, like my piddly 270 or so. I'd need thin insulation, like kapton flex or thin FR4, to do this.

Micro-coax is pretty lossy at high frequencies. Fifty in parallel would be awkward, too.