Products > Test Equipment

Smitih Charts, still relevant in 2024?

<< < (8/9) > >>

W4PJB:
I have to admit, I had intended this as a bit of a Socratic question, rather than a yes/no. But wow, I did not expect this thread to blow up so much!

Regarding the seller, yes, he was a legit engineer at a radar company. That said, it's not uncommon (especially in very large companies) for people to hyper specialize and have a very narrow scope of anything outside of their area. He was using it to measure attenuators he was selling, and perhaps that's all he did for the last 20 years in corporate as well. In which case, you're probably looking at the same screen, all day, every day.

Of course, he had something to sell and like a used car salesman who's only got one to sell, his was going to be the best. I'm sure it had a Smith chart but he sure as heck didn't know where to find it. And I wasn't going to buy a piece of test equipment from someone that doesn't know how it works. After all, how can someone like that guarantee that everything works?

Very happy with the clean 8753C I found later that evening.

Thanks for all of the replies!

joeqsmith:
I bought an AD8302 evaluation board which can measure gain and phase.   I was looking at using it to measure VSWR in the HF ham bands.  I never plotted any data from it onto a Smithchart but it was certainly possible.   In the end, I ditched measuring the phase and went with two AD8307 log amp eval boards that I mapped onto a few virtual Bird analog meters (see video).

There are similar products that the hams use today that support vectors.   
http://www.telepostinc.com/

We used to have an HP4194A gain phase analyzer where I worked.  I don't recall it supporting Smith but that's going back 35 years or so.  HP certainly had VNAs at that time and made the distinction that this product was not a VNA.   
https://www.testequipmenthq.com/datasheets/Keysight-4194A-Datasheet.pdf


joeqsmith:
Also, to further smear the lines of what is a VNA...  I have an HP 3589A Spectrum/Network analyzer.  While I (and HP apparently) don't consider it a VNA, they support using an external test set, or in my case an external directional coupler.  With this we can measure S11.  The instrument even includes Smith and supports some simple calibration. 

joeqsmith:

--- Quote from: Tation on June 23, 2024, 06:04:50 am ---An impedance matching network definitely does not use a resistor, that's wasted power.
--- End quote ---

I disagree.  It's just one more tool in the bag of tricks.  Consider that impedance matching is not constrained to antennas and power amplifiers.  We even use it when we terminate digital signals.    Let me provide you with a simple example.   In this video I am using a low cost VNA to measure a power distribution network (PDN).   Normally you would design this network for a flat impedance.   Watching at 30 minutes in: https://youtu.be/Y8ouApeex78?t=1947, I am using a target impedance of 10 ohms.   For the demonstration, I am using a plugin breadboard with various axial parts for the bypass.   Obviously this is not anything you would ever do in real life but that's not the point.  Rather it was to go over the techniques behind tuning the network.   

coppice:

--- Quote from: joeqsmith on June 23, 2024, 05:55:10 pm ---
--- Quote from: Tation on June 23, 2024, 06:04:50 am ---An impedance matching network definitely does not use a resistor, that's wasted power.
--- End quote ---
I disagree.  It's just one more tool in the bag of tricks.

--- End quote ---
3 resistors in a Y is the commonest matching network you'll see, used in millions of cheap TV antenna splitters. If it stops reflections it has achieved a match. Its just not the most efficient match.

Navigation

[0] Message Index

[#] Next page

[*] Previous page

There was an error while thanking
Thanking...
Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod