Buy a Vector Network Analyzer for low frequency

[LazySpot]

Hi

I want buy a Vector Network Analyzer, but for lower frequcy
-measurement bandwidth from several dozen kHz, up to a single MHz is enough
-measurement with a signal from about -45dBm
-shifted measuring range - the phenomena have - in relation to the background - dynamics of the order of a few to a dozen dB
-high measurement resolution of 100, 30, preferably even 10Hz
-external measurement control, (step selection of frequency subbands), preferably from PC tables
-preferably with an included external measuring bridge

VNA with this parameters are expensive because have a high frequency bandwidth, but I don't need it.

[precaud]

Low-frequency VNA's often go by the name FRA, or Frequency Response Analyser.

[nctnico]

The Anritsu MS4630B comes to mind. This has been discontinued so you have to buy it used. You'll need to use an external bridge but then again, at low frequencies you are likely better off using different measurement methods.

I don't know of any more modern pieces of test equipment that offer similar features (no, oscilloscope FRA is not a substitute for a proper network analyser). Maybe the Analog Discovery 2 could come close to a real VNA but I have not hands on experience with that.

[Kean]

Omicron Lab Bode100 - but you might not want to look at the price...
https://www.omicron-lab.com/products/vector-network-analysis/bode-100/

There is more discussion elsewhere here about alternatives, such as
https://www.eevblog.com/forum/metrology/please-suggest-alternative-for-bode100/

[egonotto]

Hi

...
-measurement with a signal from about -45dBm
...

Hello,

then the AD2 is not suitable, unless you can use a attenuator and preamplifiers.

Best Regards
egonotto

[JohnPi]

https://github.com/jp3141/Vector-Network-Analyzer might be useful

[Someone]

https://github.com/jp3141/Vector-Network-Analyzer might be useful

Yes, unless speed of measurement is critical automating a scope + signal generator is usually a good choice.

[Pitrsek]

If it's for business, Bode 100 is IMHO well worth it. If you do not need separate generator output, check https://www.sdr-kits.net/introducing-DG8SAQ-VNWA3

[RoGeorge]

https://github.com/jp3141/Vector-Network-Analyzer might be useful

Wow, searched a few times before to find a similar VNA tool for DS1054Z and generator but couldn't find any, so I was planning to wrote my own.  Thanks to your VNA on github it would be much easier now to modify that for LXI with  Rigol DS1054Z scope and DG4102 AWG.

Thanks a lot! 

[Evan.Cornell]

https://github.com/jp3141/Vector-Network-Analyzer might be useful

That is very interesting. Does anyone happen to know what it would take to adapt this to work with a Tektronix MDO3014, which has built-in function generator?

[alm]

https://github.com/jp3141/Vector-Network-Analyzer might be useful

That is very interesting. Does anyone happen to know what it would take to adapt this to work with a Tektronix MDO3014, which has built-in function generator?

It would take comparing the programming manuals for the two instruments and making some minor changes to the commands that are being sent. The script is just sending raw SCPI commands (or other commands for the SDG), so you will have to change the commands to what the MDO is expecting. The scope will probably be fairly similar, but the signal generator will probably be quite different.

What I'd do is change it to use python-ivi, which allows you to more easily switch between instruments. But that would definitely be a bigger project involving changes in both this script and in python-ivi.

[jasonRF]

Hi

...
-measurement with a signal from about -45dBm
...

Hello,

then the AD2 is not suitable, unless you can use a attenuator and preamplifiers.

Best Regards
egonotto

The AD2 is not the only scope/generator that would have that problem.  Since the OP only needs to go to 1MHz, a relatively simple op-amp based preamp would work fine.  An example using a couple of TLE2072 is in the homemade instrument thread
https://www.eevblog.com/forum/testgear/show-the-homemade-equipment-you-are-using-now/msg4500562/#msg4500562

Signal generator attenuators would be even easier to build, I would think.  Or just use the bnc attenuators you can buy from the usual places. 

jason

[2N3055]

Hi

...
-measurement with a signal from about -45dBm
...

Hello,

then the AD2 is not suitable, unless you can use a attenuator and preamplifiers.

Best Regards
egonotto

The AD2 is not the only scope/generator that would have that problem.  Since the OP only needs to go to 1MHz, a relatively simple op-amp based preamp would work fine.  An example using a couple of TLE2072 is in the homemade instrument thread
https://www.eevblog.com/forum/testgear/show-the-homemade-equipment-you-are-using-now/msg4500562/#msg4500562

Signal generator attenuators would be even easier to build, I would think.  Or just use the bnc attenuators you can buy from the usual places. 

jason

There are many scopes that have 500uV/div sensitivity up to 10V/div...
They would have no problems with 3mV P-P in Bode plot...

As opposed to AD2 having 2 ranges 0.5V/vid and 5V/div

[joeqsmith]

The fact it's a VNA you require, post some details about which S parameters, power range, sweep types, features...  You mention costs but don't provide a range. 

Not much to go on.  Then again, do your homework and maybe post which ones you have looked at and where they fell short.