The Amazon VNAs

There are a number of this type of inexpensive VNAs on Amazon, anyone used one? Is any particular one a favorite or preferable to the others? Need to do some vector impedance measurements in the 10-30MHz range. Thankee

Reply to
bitrex
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On a sunny day (Fri, 11 Dec 2020 00:09:14 -0500) it happened bitrex wrote in :

129 $

I was considering buying one a while backfor my QO100 upload that is how I found Amazon is selling Aliexpress stuff with a margin:

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59 Euro

Maybe later...

Reply to
Jan Panteltje

snipped-for-privacy@groups.io

RL

Reply to
legg

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RL

Reply to
legg

Yeah looks to be, but I don't mind paying extra ATM to get it in a couple days as opposed to someday, over the rainbow....we'll find it, the rainbow connection...ah wait those are different songs...

Reply to
bitrex

Lab grade instruments they certainly ain't. However, the obvious ideal use for them is as cheap tools for students of electronic engineering to learn all about S-parameters and the Smith Chart. For that much at least, they're unbeatable.

Reply to
Cursitor Doom

Yeah something like the hp 4191 and 4192 are on my wish list but $8000 isn't in my budget at the moment. 70db dynamic range in the low MHz is probably good enough for what I gotta do.

They all seem to be clones of the same device and the price differences is just with respect to accessories, screen size, enclosure, and the general crappy-ness or not of the knockoff.

Reply to
bitrex

At these prices probably worth paying a bit more for an aluminum housing and larger screen:

Reply to
bitrex

I got an HP 8753 series VNA with the S parameter test set for just USD1700. That series enjoys quite a following among pros and serious amateurs alike so there's plenty of advice and support on the io group forum for them. I think they're extendable up to 6Ghz but I won't be needing that as a mere hobbyist.

Nicely put! True though.

Reply to
Cursitor Doom

Did you get a screen update for this? I have one (thru work) and the screen is very dim, and I think you can get a new screen for about 500$.

Reply to
Brent Locher

On a sunny day (Fri, 11 Dec 2020 11:32:28 -0500) it happened bitrex wrote in :

I have bought only a few things from Aliexpress, but things arrived really fast here. It looks like for some stuff they have warebouses within the EU.

Reply to
Jan Panteltje

No, I haven't bothered yet. I did post a link here a couple of years ago for anyone else that might be interested, though. But no one followed up on it. When the display gets dim and you can't correct for it sufficiently in the settings of the soft menus, there's a pot on the transformer you can turn up that will buy you another five years of use. After that, it may be time to consider the colour LCD upgrade.

Reply to
Cursitor Doom

I'd like both a LF and HF analyzer but I might move on a 3577 as an interim solution, it does 5 Hz to 200 MHz, there look to be a couple for sale within 100 miles for me with the test set included for about 1k, and don't have to ship the anchor.

You can find the 8753 used for about $1500 here but don't generally include the test jig/probes/calibration modules for that price and those seem to run about as much as the box for a set (though I've read you can DIY some bits to calibrate it.) A full setup that's been calibrated by a reputable used dealer with some kind of warranty seems to run about 5k for the 8753.

Reply to
bitrex

You won't get a calibration set of standards included for that price. And the whole damn thing is useless without the S param set to go with it. Pro quality don't come cheap - unless you take your chances with the Chinese and hope for the best. They are coming on in leaps and bounds nowadays so you may get lucky.

Reply to
Cursitor Doom

The improvement in dynamic range is large even in a 30 year old boat anchor using 30 year old ADCs and DSP as compared to the $150 box from

2020, at LF it's 70dB vs 120dB for a box like the 8753.

The HP machines are using some (probably proprietary) error-reduction schemes which is what you're really paying for; putting a good-quality signal generator, ADC, DSP and display in box isn't expensive anymore the way it was in 1989.

Reply to
bitrex

All network analyzers stand or fall with their cal standards.

I have a DG8SAQ VNWA that is quite good; it not so cheap like the Chinese units but has 12-term error correction and such, and cleanly characterized standards from Rosenberger, Suhner, Amphenol and the likes. It is sold by SDR-Kits in England, there is a discussion group for it on groups.io.

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They talk a lot about calibration.

I also have an R&S ZVB-8 with a PC3.5 ECAL unit. That ECAL unit is a great thing. It removes most of the the standards changing.

But I did not jump far enough, 8 GHz is not enough for me. :-(

Cheers, Gerhard

Reply to
Gerhard Hoffmann

The same *two* devices. The S-A-A-2 (sometimes called NanoVNAv2, but unrelated to the NanoVNA) was under development when the original NanoVNA was released, and the folk who had let the design contract (to OwOComm) for S-A-A-2 decided that the market dynamics had changed enough that they should release it as open source.

There are several manufacturers of each design, with different connectors, screens and cases.

The two independent designs (and the one I was working on) share the same basic approach:

  • No filters (only the LPF of a audio-ish zero-IF receivers),
  • Two independent generators (for stimulus and LO),
  • Toggles between measuring the phase (&phase rate) between the two generators and the DUT

This approach is very sensitive to any local RF received by the DUT. I was using two DDS's for correlated sine-wave stimulus (and no switches), whereas these use square-wave stimulus signals.

CH.

Reply to
Clifford Heath

And filters. Good receivers and filters still cost a bit. If you're only testing linear devices that's less of a problem, but spurs and images limit the performance of these cheapies.

CH

Reply to
Clifford Heath

Am 13.12.20 um 02:51 schrieb Clifford Heath:

That's much like the DG8SAQ with the 2 DDS. The first versions still could rely on a printer port and sound card. Quite a long history.

Now there is a TI multi-channel codec & internal USB hub.

Gerhard

Reply to
Gerhard Hoffmann

Yes, except Baier's VNA used DDS spurs a long way above the fundamental. Quite a lot like using square waves, but using staircases instead. Mine uses AD9959, which gives you 4 channels on a 500MHz master clock.

Clifford Heath.

Reply to
Clifford Heath

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