Electrical Engineering

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Runge Kutta

00:11

Can I ask small questions here not worthy of there own post or is that frowned upon?

Shalvenay

@RungeKutta ask away

Nick Alexeev

@RungeKutta Yes, of course. That's part of the reason SE has got the chats.

Runge Kutta

00:31

I really don't understand impedance matching for transmission lines

If I look at answers to a question like "match some antenna with given R to some transmission line with characteristic impedance Z0 and given f and lamda). Then if f.e. I choose to use a capactor in series, I understand how to calculate it's value with a Smith card..

But the answers also seem to invent an input resistance of 50 ohms. And the length that you get by the smith chart is also put on another resistance of 50 ohms. Even though that number was never in the question.

I can't make sense of this.

@Shalvenay @NickAlexeev Sorry, I should probably have @ed you.

8 hours later…

Eggi

08:21

To my JTag problem, i used an USB Blaster where the line receiver was defect, an LV27A and this caused the onchip diode at the TDI pin to short against ground.

5 hours later…

Runge Kutta

13:07

Just had exam and they didn't even ask anything about impedance matching :p Still curious for a better understanding of the topic though.

1 hour later…

W5VO

14:29

@RungeKutta 50Ω is a standard impedance (as is 75Ω). It's hard to buy transmission lines that aren't standard impedance, so frequently you must match to 50Ω

Runge Kutta

14:47

Ooh, I guess I must have overcomplicated things. Thank you!

Marla

@W5VO . . If you enjoy a bit of history of early radio inovation, I just stumbled across the "barretter detector" for AM demodulator. It came before the Galena Crystal detector.

Invented by Reginald Fessenden

interestingengineering.com/…

He also invented the electrolytic detector.

3 hours later…

Marla

17:42

@Asmyldof.. . . Haven't heard from you since you were cooking that cake.