[HN Gopher] The Mysterious 50 Ohm Impedance: Where It Came from ... ___________________________________________________________________ The Mysterious 50 Ohm Impedance: Where It Came from and Why We Use It (2021) Author : amelius Score : 97 points Date : 2023-05-28 19:50 UTC (3 hours ago) (HTM) web link (resources.altium.com) (TXT) w3m dump (resources.altium.com) | userbinator wrote: | 300 ohms is also very common in applications which use | https://en.wikipedia.org/wiki/Twin-lead | myself248 wrote: | For even lower loss, ladder-line is available in 450 ohms. | kmbfjr wrote: | Which is the only replaceman open-wire feeder at 600 ohms. | They don't make it any longer, you're on your own to | construct it or make-do with ladder line. | howard941 wrote: | Yes you can definitely build your own ladder line. The | insulators are available. But it's probably easier to use | window line [0] instead. | | [0] https://www.trueladderline.com/blog/window-line-open- | wire-fe... | mordae wrote: | The article is not that good, but whatever. | | I am new to electronics myself and quite fascinated how has the | art progressed in the past hundred or so years. There are people | remembering "we were doing it wrong". Incredible. | | Anyway, if you are interested in signals traveling inside those | cute green multi-GHz boards you make your living off, go watch | Rick Hartley. | | https://www.youtube.com/watch?v=ySuUZEjARPY (How to Achieve | Proper Grounding) | | https://www.youtube.com/watch?v=QG0Apol-oj0 (What your | Differential Pairs Wish You Knew) | kurthr wrote: | I like Rick. At least they got that it was the original coax | cables that drove it. Then once you have lots of measurement | equipment and cables, it's hard to change (even SMA is 50ohm). | | You can still get 75ohm BNC cables (close to 77) and 93ohms | (and I think some 150/300ohm antenna cables?). Once you get | over a few GHz all the inputs are balanced differential anyway | and you have T networks to optimize power reflection. | | It doesn't mention at all that free space impedance that | matters a lot to actual aerial antenna design is 377ohms. I | don't know enough about it, but assume they're using | transformers to balance loads (about 300ohms?). | bowsamic wrote: | Electronics has and likely always will feel like arcane magic | to me | pclmulqdq wrote: | High-speed digital and RF are more "magical" than a lot of | other forms of electronics. It is quite a bit more | approachable if you limit yourself to ~200 MHz signals at | most, then you don't really have to worry about the RF | properties of your circuits as long as you keep the wires | pretty short. | [deleted] | nomel wrote: | It's a beautiful demonstration of how increasing one | parameter (frequency) can successively invalidate whatever | model you're using for the system, where negligible errors in | the model eventually become functional circuit components. | akiselev wrote: | That's why one of the best books on high speed digital | electronics is titled _High Speed Digital Design: A Handbook | of Black Magic_ [1] | | [1] https://www.amazon.com/High-Speed-Digital-Design- | Handbook/dp... | timemct wrote: | Especially when you think about what electronics are made of: | things mined from the earth. They made rocks compute for us! | charcircuit wrote: | Where else would they come from, the moon? It's to be | expected that for large scale products like computers to be | made from common materials. | [deleted] | al2o3cr wrote: | My favorite bit of "electronics magic": | | https://www.youtube.com/watch?v=PD7DzTIFJdU | | (this has more to do with TFA and impedance-in-general than | might meet the eye at first glance) | BenFranklin100 wrote: | Get this book: | | https://www.opencircuitsbook.com/ | | It's a book featuring macro photographs of cut-aways of | electronic components. It's the first book that helped me | really think of electronic components as a physical things | whose function followed from physical principles, rather than | an arcane collection of various bits of black magic strung | together. | CliffStoll wrote: | Windell Oskay & Eric Schlaepfer's book has brilliant | photographs and insightful text ... a coffee table book to | delight any techie. They slice through connectors, | semiconductors, and components ... showing the wonderful | microscopic world of everyday electronics. A real joy! | fxtentacle wrote: | Just a quick comment on the product, since this it effectively an | ad for Altium. | | They typically present themselves as the most popular solution, | but they also very clearly out-price any hobbyist at $10k for a | perpetual licence. Their "hobby" version CircuitStudio lacks | critical features and has 0 support and 0 updates and the forums | are just crickets. But KiCad is free, open source, and looks | similar enough that I had a great time following the Altium | tutorials by Rick Hartley with it. | | In my opinion, that also invalidates their claim that Altium is | the most commonly used PCB design software, because there likely | are 100x more hobbyists using KiCad than people able to spend | $10k on a hobby. | | It seems to me like Altium is developing like Eagle. They used to | court the makers and hobbyists and then greatly profited when | those people started working. But now both of them are mostly in | the business of milking companies who have existing data in their | proprietary file format. ___________________________________________________________________ (page generated 2023-05-28 23:00 UTC)