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Rigol RSA3000N/RSA5000N VNA software needs some work

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bayjelly:
Ah. It seems that Rigol even corrected the data sheet for that. In this data sheet from 2020, page 13 claims the range for the VNA is from 100kHz to the maximum range, albeit with a footnote that says "In S11 measurement, the performance becomes worse when the carrier frequency is smaller than 10 MHz.".

The current data sheet however just says that the range starts at 10MHz, and the footnote is gone. You can still sweep below 10MHz, though.

Both data sheet revisions show a graph for the return loss starting at 1MHz. You can see it starting out at only -15dB for 1MHz before getting better, so that should directly explain what SWR you can expect there.

Andrey_irk:

--- Quote from: bayjelly on December 30, 2022, 06:56:29 am ---
I don't know how common this is across VNAs...


--- End quote ---

Most professional VNAs have frequency ranges starting from 10MHz. The limit comes from the directional coupler architecture. There are a few exceptions from that, KS extended the E5071C's frequency limit down to 300k but the accuracy is far worse in that region.
There are resistive couplers that have very low starting frequency limit (Anritsu has that in their VNAs which go down to 70kHz), but they aren't popular because you lose quite a bit of power on them (might be other limitatins also).

switchabl:
That used to be the case with microwave VNAs but most current <20 GHz models from R&S, Keysight and also others like Copper Mountain go down into the kHz range with a somewhat degraded dynamic range. Beyond that, it's still mostly 10 MHz unless there is a separate measurement path for low frequencies (like on the PNA-X with 900 Hz LFE option).

G0HZU:
If it helps, I've been using HP/Agilent/Keysight VNAs at work all my career including the 8753/8714/E507x/PNA models.
The 8753 models can operate down to 30kHz and the 8714 and E507x models typically operate down to 300kHz although some E5071C models can work down to 9kHz. These are all models that cover up to either 3GHz, 6GHz or 8.5GHz.

There is some degradation in performance below 3MHz with these VNAs but it is fairly minor once a full cal/correction is done. By comparison, the sub 10MHz plots of the Rigol VNA look to be really awful in terms of noise. The performance looks to be really poor here.

It's generally the >=14GHz lab VNAs that are spec'd above 10MHz. Some are spec'd for use above 50MHz.

If you want to keep the Rigol RSA/VNA, I would recommend buying something like a Hugen nanovnaH for VNA use below 50MHz. These little VNAs have excellent performance across LF through to about 50MHz. If the nanovnaH doesn't have enough capability then maybe buy an old HP VNA for low frequency stuff.

EE-digger:
In keeping with the original title, I can vouch for the fact that in 2024, VNA software still needs work.

I'm in the process of returning a new RSA3015N after 2 intensive days of evaluation.  I won't go down the long list here but the final straw that broke the camel's back is that in S11, there are NO marker functions.  You can't mark a valley and  perform a bandwidth measurement, it just ain't there.

This is ridiculous that something like bandwidth of a filter (band or notch) or response of an antenna can't be measured.

This coupled with high noise below 300MHz or so in S11 are just a few of the reasons it's going back.  Rigol's support also shows that they are new to VNAs.  I will be kind and leave it at that.  Two lengthy sessions were a complete waste of time with lack of fundamentals.

Kinda sad because it seems to be a solid product, built "tighter" than Siglent, but Siglent has it all over them for speed, performance and software (with its own minor "niggles").  But taken further, if I had paid close to $10k for an RSA5065N, I would be totally pi$$ed that the product is in this shape.

added - for lower frequency S11, the Siglent SVA1032X (created from a younger sibling  ;) ) cals to under -50dB or less from 100kHz to 3.2GHz.  If you're working in the low end, then calibrate in the low end.  This will allocated more points to the cal.  The same holds true for a log sweep.  Cal and test with 1601 points or more for enough data points at the low end of the log sweep.

disclaimer:  I have not received any compensation for any glowing comments on Siglent, but would sure like to  :)  For the Rigol side, I would be glad to help with constructive input for development but at the prices being charged, the products should already be complete (more or less).

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