Measurement of Q-factor with modern hardware ? - Page 1
Forum section: electronics / projects

author: cdev
author_rank: Super Contributor
timestamp: December 07, 2018, 07:41:27 pm
content: I am wondering if anybody has used any of the newer all in one tools (for example, various newish DDSs or the ADALM2000 or Analog Discovery 2) to set up some easy automated way to measure inductor Q up to some fairly high frequency, somehow?

author: ogden
author_rank: Super Contributor
timestamp: December 07, 2018, 08:43:53 pm
content: Quote from: cdev on December 07, 2018, 07:41:27 pmDDS alone is not enough - it's just signal source. You need to add at least two phase-coherent receivers - to do RF I/V impedance analysis. ADALM2000 is 1-10MHz bode analyzer out of the box, at least they say so. Then goes some  google search results:VNA /w Analog Discovery,VNA out of Lime SDR. Looked into this just because I was interested in answer to your question as well.

author: jbb
author_rank: Super Contributor
timestamp: December 07, 2018, 10:21:02 pm
content: You might be able to find an LCR meter with communications and a high enough test frequency.

author: cdev
author_rank: Super Contributor
timestamp: December 07, 2018, 10:52:59 pm
content: Thank you for these links. Lots of interesting info at the myriadrf one especially.I wish I could afford a network analyzer. That is what I really need to do antenna stuff especially.I should try to build one from one of the projects floating around on the net.Quote from: ogden on December 07, 2018, 08:43:53 pm

author: ogden
author_rank: Super Contributor
timestamp: December 08, 2018, 01:40:19 am
content: Quote from: cdev on December 07, 2018, 10:52:59 pmVNA for antenna tuning is gigantic overkill, especially for hobbyist who say that can't afford itW2aew video below will explain how you can do occasional antenna stuff without breaking bank. His youtube channel is treasure, make sure to check other videos and obviously subscribe (i am not affiliate, just fan). Hate this forum engine which throws in thumbnail of the video - needed or not.

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: December 08, 2018, 04:19:32 am
content: I got rid of my Boonton Q-meter years ago because it was a boat anchor and I couldn't lift it. Still, that was perfect for this sort of thing.http://www.jamminpower.com/main/260A.html

author: ogden
author_rank: Super Contributor
timestamp: December 08, 2018, 09:40:21 am
content: Quote from: Conrad Hoffman on December 08, 2018, 04:19:32 am1934 yearIf <= 100KHz is ok, then better get new DER EE DE5000 RLC meter. Today plain Q is far from enough, especially if you want to know specs at/around working frequency to stick them into Spice. You better look for proper RF impedance meter then. Thou OP did not tell much details - about why he is interested just in the Q and what he consider as "high frequencies".

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: December 08, 2018, 05:47:06 pm
content: I believe the 260-A went to 50MHz, but that still won't help you with your cell phone!

author: cdev
author_rank: Super Contributor
timestamp: December 08, 2018, 06:06:34 pm
content: Quote from: ogden on December 08, 2018, 09:40:21 amI'm interested in LNAs and preselectors, and filters. And antennas, all sorts of antennas. For HF I am particularly interested in loop antennas but pretty much all antennas at all frequencies from LF to microwaves interest me. Also I am interested in antenna tuners.I have built a lot of disposable antennas to see how they work.Frequency independent antennas especially, are forgiving on exact dimensions and materials, generally, as long as you get the angles right. So they are pretty experimenter friendly.My success up until now has been mixed, but when its been good its been good enough to make me want to learn more.

author: ogden
author_rank: Super Contributor
timestamp: December 08, 2018, 07:55:41 pm
content: If so much building, then you may need <=100KHz LCR meter anyway. Also previously I forgot to mention N2PK VNA. I think I saw PCB offer for DIY'ers somewhere. Also type-in e-bay search "NWT500 50K-550MHz analyzer" - it's scalar analyzer, but maybe it's all you need.Antennas? - Sometimes you can snatch cable/antenna analyzers on fleabay for good price. Most are 1-port with just VSWR and return loss, but there are some 2-port models as well, like JDSU JD725C (JD724C is 1-port). IMHO Sitemaster and FieldFox is out of reach for hobby. For 375 .. 2700 MHz antenna/cable analysis and 1..2700 MHz SA I would suggest Agilent E7495A.

author: cdev
author_rank: Super Contributor
timestamp: December 08, 2018, 08:05:03 pm
content: Apart from the low MHz, what I've read about this device is pretty adulatory.It's almost unthinkable that a device from the 1950swould exceed anything available today!How could this be?Quote from: Conrad Hoffman on December 08, 2018, 05:47:06 pm

author: MrW0lf
author_rank: Frequent Contributor
timestamp: December 08, 2018, 08:31:08 pm
content: May be of interest for antenna stuff:FA-VA5 600MHz Vector Antenna Analyzer Kit

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: December 08, 2018, 10:36:40 pm
content: I wonder if a noise bridge would be useful? I built one that Joe Carr published in one of his books and there are certainly some online. It's a pretty easy device to build, needing just simple RF toroid plus a couple carbon pots and small caps. The noise source is a reversed bias base emitter junction of various common small signal transistors. You need a receiver, but if you're building antennas, you probably have that. You can also buy one ready to go for very little. IMO, better than any LCR type device because it gives you the values at the frequency of interest.

author: cdev
author_rank: Super Contributor
timestamp: December 08, 2018, 10:45:22 pm
content: Will do that, thanks for reminding me! (Noise bridge)

author: ogden
author_rank: Super Contributor
timestamp: December 08, 2018, 10:55:56 pm
content: Quote from: Conrad Hoffman on December 08, 2018, 10:36:40 pmMaybe as weekend fun. After fun with noise bridge you better build better VSWR device which is more up-to date, something like this:https://www.qsl.net/on7eq/projects/arduino_pwr_swr.htmhttps://www.instructables.com/id/HF-Antenna-Analyser-With-Arduino-and-DDS-Module/