Author Topic: How to build a do-it-yourself vector-network analyzer that’s actually useful  (Read 4764 times)

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Offline Free_WiFi

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no comments ...
 

Offline Free_WiFi

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It's expensive like a kidney,it's not opensource and they claim that's an DIY project  :-DD
Just LOOOOOL.
 

Offline CopperCone

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Whats wrong with this?

How much work do you think is going to get done in a university laboratory? You get a RF schematic, so that would mean you probably need to make the cables (good skill), lay the thing out/do minor mechanical work, then do calculations on the spans/signal levels to develop boundaries..

We did not even have functional chips or breadboards at my university. College kids won't be laying out RF pcb's if you just want to teach a basic class.. that would drive the instructors completely insane and manufacturing would be hard.

You probably learn things like how to plug in the components to an existing VNA to categorize them and other good skills, a good instructor can make this thing work and it can be modded. The highest frequency I worked in university was about 10MHz for a good couple of hours making a fast discrete logic gate out of a ton of transistors, and I was basically told 'this won't work right because its on a bread board'. None of the RF classes even had a laboratory component, smith charts were basically uninteresting.

It does seem like most of the effort would be in writing the program though.

It does at least look cool, it feels like you are working on something interesting and important. This is important towards keeping people interested and not just beating them with some kind of field equation. An instructor can also say alot about it, stories, etc...

« Last Edit: July 19, 2018, 07:45:15 pm by CopperCone »
 

Offline Free_WiFi

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This is PURE PILPILISM,you are talking to the wind.....
However....
this project is aimed to teach,so if it's intended for that purpose then why it's not opensource?
why they are trying to pass this bullshit like an opensource project if it's not ....
lol.
 

Offline ogden

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It's expensive like a kidney,it's not opensource and they claim that's an DIY project  :-DD
Just LOOOOOL.

Which part of "DIY for universities" you did not understood? If you expect that Minicircuits will give away their quality microwave components for free - relax. Coupler alone is 260$ worth. If you want "el-cheapo" opensource VNA, then look somewhere else.
 
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Offline Free_WiFi

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Which part of "DIY for universities" you did not understood? If you expect that Minicircuits will give away their quality microwave components for free - relax. Coupler alone is 260$ worth. If you want "el-cheapo" opensource VNA, then look somewhere else.

In the video they're saying that this "DIY" is not only for universities,but also for students ....
So i don't pretend nothing,just too much Bullshit Speech around.
 

Offline ogden

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Which part of "DIY for universities" you did not understood? If you expect that Minicircuits will give away their quality microwave components for free - relax. Coupler alone is 260$ worth. If you want "el-cheapo" opensource VNA, then look somewhere else.

In the video they're saying that this "DIY" is not only for universities,but also for students ....
So i don't pretend nothing,just too much Bullshit Speech around.

You are too occupied with "and students" part of marketing presentation that you can't see anything else in it? Look at Minicircuits offer from universities point of view. It's bargain compared to "proper 6GHz VNA".  In case you are poor student who can't afford 2500$ VNA for MIT classes, then maybe reconsider your occupation? Agriculture perhaps?
 

Online Bud

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I bet the SMA wrench alone will cost a hundred buck. Nothing is cheap at Minicircuits.

I donot know where the title came from but it is controversial at least. There are many DIY designs that ARE useful in their design frequency range, all of them in fact. The older guy in the video should get a life. 
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Offline ogden

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You are too occupied with "and students" part of marketing presentation that you can't see anything else in it? Look at Minicircuits offer from universities point of view. It's bargain compared to "proper 6GHz VNA".  In case you are poor student who can't afford 2500$ VNA for MIT classes, then maybe reconsider your occupation? Agriculture perhaps?

There are lot of seemingly way too expensive products around. So what? Just buy something you can afford and don't whine.


 

Online Bud

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And by the way, while the demonstrated contraption may be useful, it is the Least Practical design i have ever seen. You need a power supply for it (guess a bench one will be recommended). , it takes a wack of space on the bench, you can't take it to the field or on the roof, etc. Oh yeah, they omited cost of a calibration kit on purpose.
Facebook-free life and Rigol-free shack.
 
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Offline ogden

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And by the way, while the demonstrated contraption may be useful, it is the Least Practical design i have ever seen. You need a power supply for it (guess a bench one will be recommended). , it takes a wack of space on the bench, you can't take it to the field or on the roof, etc. Oh yeah, they omited cost of a calibration kit on purpose.

Most of university lab contraptions are not practical for field use  :-DD

You shall get a life as well [wasntme]
 
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Offline wraper

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it takes a wack of space on the bench, you can't take it to the field or on the roof, etc. Oh yeah, they omited cost of a calibration kit on purpose.
Why the hell do you even assume it is supposed to be taken to the field? It's a learning platform and also could be used as development platform. Hobbyists and normal VNA users certainly are not the target audience.
 

Online hendorog

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And by the way, while the demonstrated contraption may be useful, it is the Least Practical design i have ever seen. You need a power supply for it (guess a bench one will be recommended). , it takes a wack of space on the bench, you can't take it to the field or on the roof, etc. Oh yeah, they omited cost of a calibration kit on purpose.

Actually the Cal kit is included. It looks like its USB powered.

https://www.minicircuits.com/pdfs/UVNA-63.pdf
 
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Offline drew23

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There is more information available. The kit costs around $2500 and will be shipping in September. No mention of code availability. It is list as a first project, so there may be more to come. The transceiver board seems very capable.

https://www.minicircuits.com/WebStore/uvna_63.html
 

Online Bud

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Because the title says "....actually useful". I have my interpretation of the term "useful" affer 35 years in RF.
Facebook-free life and Rigol-free shack.
 
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Offline wraper

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Hmm, that chip on the PCB is 3D RF imager... The same as used in Walabot.
 

Offline Sparky49

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I buy a couple of tins of paint and some wood panels to do some diy in my living room. I don't expect the paint manufacturer to give me the ingredients and procedure to recreate the paint from scratch, and I don't expect the wood manufacturer to tell me how to grow my own trees. Yet I spend a bit of money to buy the items to perform diy.

It's the same here. Minicircuits are providing a kit, which can be assembled together yourself, if you pay for it. Why does it need to be open source when they aren't calling it open source? They are providing a kit for a niche market, which the vast majority of electronic hobbyists are not included. This isn't uncommon. Terasic sell dev kits for thousands of dollars. So do many other manufacturers: microchip, linear, etc. Most are far overpriced and are not intended for hobbyists.

This is firmly aimed at the university market, for the use of (not purchase!) students and possibly researchers. It is not very practical, but it is not intended to be a great VNA, its a relatively cheap, complete kit for universities to buy. Universities by and large don't wince at such price tags, as they will have budgets to spend and the real deal is the time it saves in preparing work for students. If I was a prof working on some interesting labs for my students, buy several of these kits might be quite appealing as I don't have to waste time researching all the bits and ensuring they will work myself. This is often the primary selling point, and where it is actually "useful", though I do sometimes wish things weren't quite so expensive.  :-[

Sometimes the bean counters are wrong, but if the product is a flop for its chosen target market then we might see it withdrawn ;)
« Last Edit: July 19, 2018, 10:14:24 pm by Sparky49 »
 

Offline Free_WiFi

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If this kit is not opensource,then how can you pretend that students will learn something from this "EDUCATIONAL DIY"?
 

Offline wraper

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If this kit is not opensource,then how can you pretend that students will learn something from this "EDUCATIONAL DIY"?
How do students learn by using non opensource oscilloscope? How dare people use Raspberry pi in their DIY projects? Hardware is not open!!! Students learn principles how VNA works using some level of abstraction. It's not like they could make their own board even if they had full schematic and gerber files.
« Last Edit: July 19, 2018, 10:38:10 pm by wraper »
 
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Offline CopperCone

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Did you guys have like billion dollar university laboratories or something that you are complaining about layers of abstraction with this beast?

Did anyone here actually do anything more then a breadboard with low frequency stuff and maybe a MCU on it at university apart from independent research projects that you need to beg the department to allow you to do for credits? The most advanced RF project I saw for undergraduates at my university was some kid designing op-amp active filters that work at some where like 30MHz @ low signal power levels.. he got access to a spectrum analyzer and a few hours training. I think a few classes used zig-bee's you can shove on a breadboard for some control systems stuff. You had to be friends with the laboratory people and proven responsible to even be allowed near the spectrum analyzer.

Maybe graduate students do it more...

I think where I went to school they would scratch the labels off the mini-circuits boxes so people don't steal them.
« Last Edit: July 19, 2018, 11:06:05 pm by CopperCone »
 

Online hendorog

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DIY in this case refers to DIY implementation of the VNA equations. I.e. work out the code to implement the equations which you have derived in your study.

They mention Matlab (or was it Labview) and Python for doing so.
 

Online chris_leyson

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If you want it cheap and 6GHz then go go build this http://hforsten.com/cheap-homemade-30-mhz-6-ghz-vector-network-analyzer.html If you want it really easy to build then get the minicircuits design.
If you want to build a DIY 6GHz VNA then at least make an effort to understand the principles and practicalities involved. Any serious practicing RF engineer wouldn't bother wasting time building a spectrum analyzer let alone a VNA. Maybe you should do some more background reading into wideband RF design and then you might understand the difficulties involved. Maybe this should have been posted in the beginers section.
« Last Edit: July 20, 2018, 12:56:29 am by chris_leyson »
 

Offline drew23

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 Mini Circuits webpage says "access to free online tutorials and sample code, coming soon". I think the page came up in the last few days. The support materials may be useful. Shall have to wait and see. It would be good if the TRX board were available separately.
 

Offline Mechatrommer

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its more proper to say it a "modular" or "educational" VNA. well i'm feeling lucky to get a "ready working" VNA for more BW and accessories and alot lesser price tag, no need to diy build myself stuffs. it has quirks but thats what a students sector for to build equations and diagnosis the trouble to enhance knowledge bla bla.. good luck getting a good coupler respond if you are going to build one. you need a VNA to build a VNA...
if something can select, how cant it be intelligent? if something is intelligent, how cant it exist?
 

Offline TheUnnamedNewbie

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Free_WiFi, you seem to have little grip of what matters in teaching.

You want to teach one step at a time - in this case they can start by building it by themselves, which gives them some practical experience most students don't have during their university career (microwave components are just too expensive). The software is the key here - this would be an amazing project to have students implement the actual equations to go from signal levels from a few power sensors to transmission/reflection, and to learn different calibration algorithms. And because everything is built out of blocks, a more advanced and larger team project could then allow them to design their own PCBs for the couplers and that will give them some experience there too.

This is a great thing, and I am excited to look at getting our hands on one to see if we can integrate it in the coursework I will teach next semester. If you feel like you can do it better, that is good for you, and I wish you the best of luck. Nobody said it has to be a very high quality VNA, it has to be a teaching tool. But it does seem to do an amazing job in finding the balance between modularity, flexibility and effort that needs to be done for a teaching tool.

And regarding open-source: As long as they have a good driver, I'm happy. I don't feel a need to go write my own, or have the students write their own - it is clearly not the subject this kit will try to teach.
The best part about magic is when it stops being magic and becomes science instead
 
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