EEVblog #343 – Spectrum Analyser Tracking Generator TutorialPosted on August 30th, 2012 12 comments
Forum Topic HERE
Testing the frequency response of an LC Pi (Capacitor-Input) low pass filter with a Rigol DSA815-TG Spectrum Analyser with Tracking Generator Option.
Inductor Datasheet HERE
That was a great video! Can you please show how you can do the same thing with a function generator and a scope?
Great video. Been looking for a Spectrum Analyzer. Would you recommend the Rigol DSA815-TG? Looks like a great tool for the price. Any pros or cons?
Enjoyed the video.
What would you expect the impact to be of increasing the number of components in the pi filter.
Great. One can’t find most of what you show us in books. There few books on spectrum analysis anyway, and almost no good ones. This is the lab and shop version of tribal knowledge that we our being gifted with here.
Too bad you claim to not be a “radio guy,” since RF is were Analysers are really needed. Please do more tutorials before you do a teardown and return this.
On a more general note, thanks to the people in the Rigol, Agilent, etc. distribution chains that send you these devices. I bought a Rigol DS1102E/DG1022 Scope & ArbGen combination for my home bench right after your old teardown of the DS1052E Scope. And I will probably buy this Analyser to replace my 15 year old Advantest unit soon.
I’m interested in what the flatness looks like with a decent coax jumper. All of that ripple looks like an impedance mismatch.
You really should normalize each time you change the span and scale; especially the span. That toothiness with some symmetry in the tracking generator looks like DDS artifact, it isn’t periodic as might be expected with return loss issues.
Using the tracking generator with a pre-amp stage on is dicey, especially for wide dynamic range measurements and measurements with more than one spectral component – compression, intermodulation, general nastiness can be introduced by the pre-amp.
In-fact I would turn off the pre-amp for the type of two port measurement you were demonstrating.
For the inductor, choose your material carefully and it (hopefully) will help to frequency limit below self-resonance. Perhaps something like an T30-2 iron powder toroid (red) with a dozen or so turns? However for such a large measurement bandwidth to resonant frequency ratio, you may need to add a second stage low-pass and/or some gimmick caps to squash the peaks.
I would expect to see a narrower self resonance than what you were seeing, but all bets are off unless you re-normalize.
Thanks for the vid Dave…
Dave, I know this is probably beyond time and interest (and even equipment?) you have to do but well it’s something “fun” which could bring a lot of audience if you find something interesting.
Back in mid-naughties, PC hw benchmark sites like anandtech tested (and still do) a lot of motherboards. With CPU running at identical clock the results were usually quite identical but there was still some miniscule variation. Then the motherboard makes started tweaking the defaults to make theirs mb run CPU or bus or something faster and it was all noted.
But when the latest Intel cpu’s architectured arrive, it brought some changes to this to my best understanding and now the hardware sites are giving out the impression that all their test setups are equal (we don’t get to see what kind of clocks the boards are really running), yet the differences between just switching a motherboard (many having identical components from same manufacturers) are still there.
The impression the comparison/test articles are giving out is that there’s no “shady” clocking going on and some motherboards are just faster than others. I think that’s complete bollocks and would be fun if someone with access to multi-ghz equipment would probe around two different brand motherboards with same chips and BIOS showing same clocks etc with exactly same CPU etc… and see where the extra speed is coming from.
The brands which are typically “faster” or “better” tend to be same every year, I think there’s some consistent cheating (overclocking things but not telling users) going on there.
It would take some work to find right boards for this testing (might be faster to ask some guy at the hardware sites assuming they have memorized all the specs lol) as I haven’t kept up with all the reviews recently but if you have interest for such “mythbusting” then I might put the few hours or more to find the candidate boards. There’s literally hundred of board specs to look. Ideally it would be board from either Asus, Asrock, Gigabyte as these are some of the big players with identical chips but notably different benchmark results.
Great video. Please film more on the operation of other test equipment as well. Thank you.
Could you PLEASE make a review on the 815-TG and
give us more details in how to use a spectrum analyser?
THANK YOU in advance!
Leave a reply