100kHz to 6GHz 2 port USB based VNA | Hacker News Reader

100kHz to 6GHz 2 port USB based VNA

github.com

112 pointssleepingreset29 comments

A Vector Network Analyzer - https://en.wikipedia.org/wiki/Network_analyzer_(electrical)

First paragraph of the Overview section is borked:

Network analyzers are used mostly at high frequencies; operating frequencies can range from 1 Hz to 1.5 THz. Special types of network analyzers can also cover lower frequency ranges down to 1 Hz.

What's the first figure supposed to be?

Most likely 10 MHz. The reference links to Keysight.com and that's more or less industry standard for compensated directional couplers which are used in the large high performance VNAs. To go lower than that they usually use a directional bridge.

Fun facts, you can build your own VNA from scratch using open source GNU Radio toolkit with any off-the-shelf SDR platform for example using the low-cost ADALM-Pluto or you can go fully gung ho with the more capable RFSoC platform [1],[2],[3],[4]:

[1] Lab notebook of experiments in GNURadio:

http://www.swigerco.com/gnuradio/

[2] Off-the-Shelf Reconfigurable Software Define Radio Approach for Vector Network Analyzer:

https://jati.apu.edu.my/files/2018/12/2018_Issue2_Paper1.pdf

[3] ADALM-PLUTO: Software-Defined Radio Active Learning Module (USD230):

https://www.analog.com/en/resources/evaluation-hardware-and-...

[4] RFSoC 4x2 Development Kit Overview (USD2K):

https://news.ycombinator.com/item?id=39427825

VNAs are fundamentally narrow-band instruments. This:

> The RFsoC 4x2 board has 4x RF ADCs (5 GSPS) and 2x RF DACs (9.85 GSPS)

is like chasing after a fly with a sledgehammer. It wildly over-specs something that is almost completely useless for the task at hand (real time bandwidth, mass of hammer) while it wildly under-specs the important parts (frequency range, directivity, agility of hammer).

If you have the RFSoC the VNA is the low hanging fruit.

If you're doing modern wireless systems measurement and testing (4G/5G) most likely you will need spectrum analyzer (SA), vector signal analyzer (VSA) and vector signal generator (VSG).

The cost of all the disparate systems namely VNA + SA + VSA + VSG will easily cost north of USD100K for the used ones and multiple times more for the new ones. With the low cost RFSoC platform together with the standard RF test kit (attenuater, pre-amp, multiplexer, switch, etc) you are pretty good to go.

It's really perplexing that no one including the Chinese are trying to disrupt this industry, Keysight and R&S are currently charging arms and legs for their equipments even the basic one like VNA.

> It's really perplexing that no one including the Chinese are trying to disrupt this industry

No point.

1) Low volumes

These things never really go obsolete and the replacement rates are abysmal.

2) Race to the bottom

Once you disrupt it, everybody sees that you disrupted it, and everybody clones you and piles in.

Customer support is the only differentiator. To fund that, you have to charge north of $10K per unit--generally north of $25K.

Tektronix found this out the hard way with their real time spectrum analyzers. It was a nice disruption at the $5K point. Lots of people bought them. Then demand dropped like a rock because everybody who needed one bought one. And because the revenue crashed Tektronix laid off the development group--who are also the same people you need for advanced customer support.

siglent is moving in on VNAs a bit but i absolutely agree. as a ham i could do with all of above :-)

>low-cost ADALM-Pluto

~$250, meanwhile Chinese nanoVNA clones are ~$25-40, add prescaler and you can reach 6GHz.

Anecdotally I have seen nanoVNAs being used with directional antennas in Ukraine as crude drone finders. https://www.reddit.com/r/CombatFootage/comments/1afspa8/comb...

Very late reply but that is most likely a tinySA, a compact and inexpensive spectrum analyzer that uses the same case as many nanoVNAs: https://www.tinysa.org/

Wow, that RFSoC board is incredibly cheap - ours cost $12K or so, and we needed special approval too under defence regulations.

> or you can go fully gung ho with the more capable RFSoC platform

You can't:

> The RFSOC 4x2 is currently only available to staff at accredited Universities and Research Institutes.

If you go to the Real Digital site (vendor that makes the board), they appear to also sell it commercially, albeit at the higher price of ~$4k (compared to their academic pricing of ~$2k).

this VNA is super great. for $600 you get up to 8Ghz (not a typo, 8GHz can be archived in harmonic mode) usable range. with two of them you can do 4port measurement. you can also produce time domain reflectometry with it. open source hardware, firmware, fpga and pc side software.

This is insane. The project includes the hardware (GHz-capable RF-generation and measurement), firmware (FPGA) and Software (a cpp GUI). Surely that can't be all from one person?

It's under development close to 4 years. If the person has time (or doing Ph.D. or something on the subject), this is a very viable time frame to do all of this.

There are other people's work in it, but it's a one man show mainly.

This is a passion project and it shows.

Edit: Plus, this is the second iteration of the hardware. First iteration is at https://github.com/jankae/VNA

It's not that hard (not that it's easy either!). The individual parts are conceptually relatively simple, the devil is all in the details. For a generalist this is a doable, but likely very time consuming project. I've done something similar (fairly different focus in purpose and specs, but the overall shape and scope is not much off) professionally, mostly on my own.

"Surely that can't be all from one person?"

It's possible. Especially if they aren't a piece of shit like me.

Are we the same person?

I guess that's the existential question - is one pos really any different from anotherin a meaningful way; is any person in general?

This is cool, it'll be nice to have an alterative to the NanoVNA, and it looks like you've got a bit more dynamic range, as a bonus.

It's not really an alternative at 4× the cost of the NanoVNA. It's more like an upgrade.

It's not 4x the cost of a real NanoVNA, it's 4x the cost of a clone.

I'm talking about open-sourced-ness though.

Very impressive.

One minor nit: the page is for some unfathomable reason not zoomable on mobile (Chrome on Android), making the schematics hard to read. Extra annoying when you click it and get the SVG source (which means it would zoom perfectly).

In chrome mobile you can go to the settings > accessibility > force enable zoom.

Great tip! I realized I was actually viewing the page in the Github app, so ... still no zoom. :/

This is very cool. I’ve been looking at VNAs to start making my own antennas for my Meshtastic devices.

Beautiful stuff!

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