Capacitors at RF

I can think of one electronics-related field where Australia has done world class work: Cochlear implants. John

Aussies have claimed that they won't drink Fosters themselves, that they only manufacture it for export, like coal. If so, they still do a lot of damage.

They make some truly awful brews. All chemical compositions I believe: Castlemain, Fosters, VB (Vomit Bomb) and such like. All guaranteed to trash your IQ and cognitive functioning.

Tom Gardner wrote: ======================

Large electros are easiest measured by the rate of rise of voltage at a given current.

..... Phil

Accursed Dope wrote: =======================

• Correct, I hate trolls like you.

You got up in the middle of the night just to say that??

Bill Sloman wrote: ===============

He haunts NGs like "aus.legal" , "aus.politics" and "aus.aviation" - while having no friend on any of them.

Mr Speed expresses the strongest opinions on every topic he thoroughly misunderstands. He is also a master of the false argument - no logical fallacy escapes him.

I believe I met him once, in the late 70s and he is a former NSW traffic cop. Same odd name (Speed cop?) right age and with the same hostile attitude & feigning deep knowledge of the law while possessing almost none.

Rod is so *notorious* that someone created a "bot" using his debating style and repetitive phrases.

Many swear it is indistinguishable from the real thing.

...... Phil

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This is almost entirely due to the length of the part and the enclosed loop area of current flow. Also, Q values are VERY low - unlike other capacitors.

It always amuses me seeing folk put 0.1uF caps in parallel with electros to cure " self inductance".

FYI:

The above practice likely derives from tube radios, where paper caps were paralleled with filter electros to lower the ESR. Back in the day, an 8uF, 400V cap might have 12 ohms ESR allowing LO signal to leak into other stages.

..... Phil

I've had contact with Rod Speed in Usenet groups (I forget which - it was years ago). None of the trolls in this group come close to his level. Even John Doe is an amateur in comparison.

I played with that chatbot for a while. It is easily distinguishable from the real thing after a few appropriate comments and questions. Especially questions. But it was fun until I became bored.

Can you measure the C, esr, and esl? You can get values for them, and to what precision? If so, I'll have to try it.

Yes. And I've measured mine with a frequency counter and the dial is exactly on. I love it.

C is the gross slope or time constant against 50 ohms. ESR is often in plain sight.

ESL can be estimated from ringing frequency or the area under a low-Q overshoot spike. The old Tek 1S2 manual has a good section on this. I'll look for it downstairs.

You're looking at lines on a screen, so it won't be super precise. But it can be very useful. Things like TDRing fet gates or inductors or connector transitions can be fun.

Sometimes I play with a Spice sim until it looks like the TDR waveform.

Yes. I understand what to look for there. I've just never tried to calculate a value from what I see. I've seen the the spike of the ESL then the ESR step then the capacitor slope.

All this stuff is fun. And frequently enlightening. However, I don't have the equipment to do anything serious. My work is primarily low speed stuff but I would like to test some of the components I buy using TDR rather than frequency methods.

That sounds useful. I'll have to give it a try.

I have a very old Tek 11802 that does 30 ps TDR and has measurement cursors. It's great for checking PC boards.

You can make your own roughly 2 ns TDR with a fast gate and a modest Rigol scope. One step response means so much more to me than a mess of Smith charts or S-params.

I have a an Instek 200MHz, 1gb sample/sec. Is that modest enough?

That has a rise time around 1.8 ns. A Tiny Logic gate can do about 500 ps as the step source. The net TDR rise time will be below 2 ns.

I think there are examples online. It's not hard to do.

Cursitor Doom must be envious.

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t the frequency you'd use to measure 10,000uF electolytic.

From our point of view, inhabitants of the northern hemisphere have the sam e problem. The weird poisonous creatures are different - Donald Trump and B oris Johnson don't have exact equivalents in Australian politics. Scott Mor rison - also known as Scotty from Marketing - has other defects, but he's p robably less poisonous.

in damage.

Quite a few of us aren't descended from criminals. I can name all my ancest ors who emmigrated to Australia, and none of them were convicted criminals.

Australian beer does contain ethanol and that does damage the brain. Some o f it contains more ethanol than US beer, which could be seen as making it m ore brain-damaging, until you pay attention to the other contents.

American water can be more damaging - as in Flint Michigan

Very poisonous politicians.