Re: OT: Covid's True Origins

On Wed, 23 Apr 2025 07:38:48 -0700, john larkin <jl@glen--canyon.com>
wrote:

On Wed, 23 Apr 2025 11:56:39 +0100, Cursitor Doom <cd@notformail.com>
wrote:
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On Tue, 22 Apr 2025 16:29:22 -0700, john larkin <jl@glen--canyon.com>
wrote:
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On Tue, 22 Apr 2025 15:15:01 -0700, john larkin <jl@glen--canyon.com>
wrote:
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On Tue, 22 Apr 2025 22:02:32 +0100, Cursitor Doom <cd@notformail.com>
wrote:
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On Mon, 21 Apr 2025 15:02:17 -0700, john larkin <jl@glen--canyon.com>
wrote:
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On Mon, 21 Apr 2025 22:23:03 +0100, Cursitor Doom <cd@notformail.com>
wrote:
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On Mon, 21 Apr 2025 08:26:40 -0700, john larkin <jl@glen--canyon.com>
wrote:
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[...]

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?

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Periodic waveforms are all boring. They just do the same thing, over
and over.
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A complex pulse can do interesting things. Spin an airplane. Fuse
deuterium-tritium. Trigger a megaton boom.
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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.

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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!

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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/

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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."

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

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

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I can usually take a few points on a breadboard or an eval board.
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Many RF parts self-bias, or are more complex than a classic 3-terminal
part.
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Even worse, some have internal closed-loop bias things of undefined
bandwidth. I hate that.
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The RF boys always chop off their graphs to hide the bad bits. And a
lot of parts are sold to work in some specific band, with tuned wire
bonds or whatever, so wideband use is guesswork.

I feel your pain. Life's a *bitch* at mm wave. Am I allowed to say
that any more? Oh well, tough - I just did.

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.
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Testing a $300 distributed amplifier chip for its genuine abs max
output voltage limit is emotionally tricky.

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

>
I used the HMC659 in the recent NIF modulator project. They are over
$300 each. If you pull the output up with a current source and poke
negative pulses into the input, it breaks down at about 16 volts. That
was an interesting experiment.

If you want to *fully* characterize such devices, it will cost a small
fortune. But depending on the application, you may have to lay out the
bread, because as you've already said, there's a paucity of
information in the typical datasheet when it comes to 'extreme'
operating conditions.

Breaking things is fun. Well, cheap things.

Or expensive things that a crowd of other people have paid for, yes.