Author Topic: Measurement of Q-factor with modern hardware ?  (Read 818 times)

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Offline cdev

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Measurement of Q-factor with modern hardware ?
« on: December 07, 2018, 07:41:27 pm »
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?

"What the large print giveth, the small print taketh away."
 

Offline ogden

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Re: Measurement of Q-factor with modern hardware ?
« Reply #1 on: December 07, 2018, 08:43:53 pm »
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?

DDS 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 [unverified] 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.
 
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Online jbb

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Re: Measurement of Q-factor with modern hardware ?
« Reply #2 on: December 07, 2018, 10:21:02 pm »
You might be able to find an LCR meter with communications and a high enough test frequency.
 

Offline cdev

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Re: Measurement of Q-factor with modern hardware ?
« Reply #3 on: December 07, 2018, 10:52:59 pm »
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.

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?

DDS 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 [unverified] 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.
"What the large print giveth, the small print taketh away."
 

Offline ogden

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Re: Measurement of Q-factor with modern hardware ?
« Reply #4 on: December 08, 2018, 01:40:19 am »
I wish I could afford a network analyzer. That is what I really need to do antenna stuff especially.

VNA for antenna tuning is gigantic overkill, especially for hobbyist who say that can't afford it ;) W2aew 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).



[edit] Hate this forum engine which throws in thumbnail of the video - needed or not.
« Last Edit: December 08, 2018, 01:42:06 am by ogden »
 

Offline Conrad Hoffman

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Re: Measurement of Q-factor with modern hardware ?
« Reply #5 on: December 08, 2018, 04:19:32 am »
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
 

Offline ogden

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Re: Measurement of Q-factor with modern hardware ?
« Reply #6 on: December 08, 2018, 09:40:21 am »
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.

1934 year :)

If  <= 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".
« Last Edit: December 08, 2018, 09:12:15 pm by ogden »
 

Offline Conrad Hoffman

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Re: Measurement of Q-factor with modern hardware ?
« Reply #7 on: December 08, 2018, 05:47:06 pm »
I believe the 260-A went to 50 MHz, but that still won't help you with your cell phone!
 

Offline cdev

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Re: Measurement of Q-factor with modern hardware ?
« Reply #8 on: December 08, 2018, 06:06:34 pm »
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.

1934 year :)

I am afraid that this instrument do not qualify because 50KHz cannot be considered as high frequency. If 50KHz 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".

I'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.
« Last Edit: December 08, 2018, 06:26:01 pm by cdev »
"What the large print giveth, the small print taketh away."
 

Offline ogden

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Re: Measurement of Q-factor with modern hardware ?
« Reply #9 on: December 08, 2018, 07:55:41 pm »
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.
 

Offline cdev

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Re: Measurement of Q-factor with modern hardware ?
« Reply #10 on: December 08, 2018, 08:05:03 pm »
Apart from the low MHz, what I've read about this device is pretty adulatory.

It's almost unthinkable that a device from the 1950s would exceed anything available today!

How could this be?


I believe the 260-A went to 50 MHz
« Last Edit: December 08, 2018, 08:52:54 pm by cdev »
"What the large print giveth, the small print taketh away."
 

Offline MrW0lf

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Re: Measurement of Q-factor with modern hardware ?
« Reply #11 on: December 08, 2018, 08:31:08 pm »
May be of interest for antenna stuff:

FA-VA5 600MHz Vector Antenna Analyzer Kit



 

Offline Conrad Hoffman

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Re: Measurement of Q-factor with modern hardware ?
« Reply #12 on: December 08, 2018, 10:36:40 pm »
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.
 
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Offline cdev

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Re: Measurement of Q-factor with modern hardware ?
« Reply #13 on: December 08, 2018, 10:45:22 pm »
Will do that, thanks for reminding me! (Noise bridge)

 
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Offline ogden

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Re: Measurement of Q-factor with modern hardware ?
« Reply #14 on: December 08, 2018, 10:55:56 pm »
I wonder if a noise bridge would be useful?

Maybe 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.htm

https://www.instructables.com/id/HF-Antenna-Analyser-With-Arduino-and-DDS-Module/
 
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