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From: Cursitor Doom <cd@notformail.com>
Newsgroups: sci.electronics.design
Subject: Re: OT: Covid's True Origins
Date: Wed, 23 Apr 2025 11:56:39 +0100
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On Tue, 22 Apr 2025 16:29:22 -0700, john larkin <jl@glen--canyon.com>
wrote:

>On Tue, 22 Apr 2025 15:15:01 -0700, john larkin <jl@glen--canyon.com>
>wrote:
>
>>On Tue, 22 Apr 2025 22:02:32 +0100, Cursitor Doom <cd@notformail.com>
>>wrote:
>>
>>>On Mon, 21 Apr 2025 15:02:17 -0700, john larkin <jl@glen--canyon.com>
>>>wrote:
>>>
>>>>On Mon, 21 Apr 2025 22:23:03 +0100, Cursitor Doom <cd@notformail.com>
>>>>wrote:
>>>>
>>>>>On Mon, 21 Apr 2025 08:26:40 -0700, john larkin <jl@glen--canyon.com>
>>>>>wrote:
>>>>>
>>>>>[...]
>>>>>>Sine waves are boring.
>>>>>
>>>>>Well, square waves give rise to lots of harmonics which can be useful.
>>>>>But what about triangles and sawtooths. Any interesting properies
>>>>>hidden away in those?
>>>>
>>>>Periodic waveforms are all boring. They just do the same thing, over
>>>>and over.
>>>>
>>>>A complex pulse can do interesting things. Spin an airplane. Fuse
>>>>deuterium-tritium. Trigger a megaton boom.
>>>>
>>>>I wish the world would move on from the slide rule and graph paper
>>>>days, narrowband s-parameters and Smith charts and load pulls. We have
>>>>computers now.
>>>
>>>It's dumb *not* to use computers for the complicated and trap-ridden
>>>calculations relating to impedance transformations, filters and
>>>transmission lines. *However* if someone using computers for this
>>>purpose hasn't been schooled in the derivation of the calculations by
>>>learning how the Smith Chart was developed and how it got that scary,
>>>warped shape, then they're going to be too far abstracted from the
>>>underlying physics to be able to understand fully what's going on
>>>under the hood. And they'll be that much poorer for it. Like people
>>>who use rules-based calculus to solve problems because they have
>>>little understanding of the nuts and bolts of derivatives and
>>>integrals. Ask them to solve a new problem and they're lost!
>>
>>No, don't just automate the antique concepts. We need Spice For RF,
>>genuine wideband time-domain analysis. Anything interesting is
>>nonlinear anyhow.
>>
>>https://www.ineltek.com/en/qorvo-qspice-neues-simulationstool-fuer-rf-und-leistungselektronik-schaltungsdesigns/
>
>I develop my own Spice models for MMICs and phemts and distributed
>amplifiers and other RF parts. That usually involves measurements,
>because most RF parts don't even specify DC things. Some data sheets
>say "adjust the bias until it works" or "ac couple the input and
>output."

Yes, they're generally poor on detail for sure.

>I drive electro-optical modulators with narrow pulses. The RF part
>data sheets assume a continous, symmetrical sine wave. I can get twice
>the swing for pulses if I bias a distributed amp way off-center.

You should get yourself a curve-tracer - or design one (and share that
with me so I can build one).:)

>RF parts seem to specify their abs max voltage assuming that a sine
>wave might swing from ground to 2xVcc, but the data sheet specifies
>abs max Vcc. So one has to cheat.
>
>Testing a $300 distributed amplifier chip for its genuine abs max
>output voltage limit is emotionally tricky.

I would imagine so, yes. However, at least today you can launch a
crowd-funding appeal to share the burden. ;-)