NanoVNA V2: An Inexpensive and Effective Vector Network Analyser

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NanoVNA V2: An Inexpensive and Effective Vector Network Analyser

Postby OverTheTop » Fri Oct 02, 2020 8:53 pm

NanoVNA V2: An Inexpensive and Effective Vector Network Analyser

I recently found that I was able to purchase a Vector Network Analyser (VNA) or the princely sum of only around $120, thanks to the wonders of modern electronics. Brand new, functioning and virtually ready to go out of the box. Putting this in perspective we have a couple where I work. We have a small portable unit (FIeldFox) that performs reasonably well and costs around $10k. We have another bench unit that will cost you $58k new, and we have a third one that is even more expensive. So, to get something that is reasonable for around $120 is amazing. Bottom and top frequencies don’t quite make it to where the more expensive units are but they are still very useful, especially in the area of the spectrum where we like to work with telemetry and GPS.

What is a VNA?
A Vector Network Analyser is basically an instrument that can be used to analyse networks of radio frequency (RF) components. When we say networks it is nothing like a computer network. We are essentially talking about a black box (unknown components inside) that might have connections in and out. The VNA is able to analyse how the network behaves at various RF frequencies and provide information on how much power is transmitted through, or reflected back from the connections, without knowing exactly what is inside the network. So even though we don’t know what is in the network exactly, we can measure how it affects signals we pass through it. In our case we could be testing a cable, a filter or perhaps an antenna.

This ability makes it very useful measuring the performance of antennas to some degree and also checking our antenna cables are behaving nicely.

How does a VNA do this? It is essentially a transmitter and two receivers that allow the comparison of the transmitted signal and the received signal. There are some clever devices called directional couplers in it which allow it to measure the power in each direction, forward and reflected. Both amplitude and phase are measured, hence the “vector” in the name. There are other scalar network analysers that just look at the amplitudes but the VNA is more versatile and at this price why wouldn’t you?

The frequency range of this device is from 50kHz to 3GHz. Very good for a bargain-priced unit.

Note that I have the V2 (version 2) of the NanoVNA. The original did not have as wide a frequency range and was technically inferior to this later version.

Here is where you can purchase the NanoVNA V2 and support the developers. There are clones available on some websites that may be cheaper but quality and performance can vary.
https://nanorfe.com/nanovna-v2.html
https://www.tindie.com/products/hcxqsgroup/nanovna-v2/
When ordering make sure you get the cable and calibration kits with the unit. It is pretty useless without those. The unit does need to be calibrated whenever you change the frequency settings, but the process is quite painless.

I would also recommend getting some “connector savers” that screw onto the VNA ports. The SMA connectors used (in fact all connectors) have a finite life and each insertion/removal takes it a step closer to its limit. By fitting the connector saver adapters you can replace them when the connectors wear out, as replacing the VNA connectors which are soldered on is a much more serious task.
https://www.ebay.com.au/itm/5-x-SMA-fem ... 3094372441
These connectors are fitted permanently to the existing SMA connectors on the unit and left there until they are worn out.

There are some video tutorials for the NanoVNA on this site:
https://www.rtl-sdr.com/tag/nanovna-v2/

Here is a pic of the cables and calibration kit. There are short, open, through and load (50ohm) connectors in the cal kit.
Cables.jpg

The VNA comes with two PCAs. One is the main board and the other the touch-screen display. Note that as supplied you can run it off a USB cable directly, but if you want to use it without external power you need to provide a suitable battery. They don't ship batteries to keep the hassle of DG shipping LiPos out of the transaction. There is a connector for the battery and charging circuitry is inbuilt. Note that this unit can run standalone with a battery, or it can be run off a PC with the VNA controlled from there as well, and results are able to be exported.

VNAinCase.jpg

It comes with a fairly basic plastic case (if you order it). It is a bit agricultural but it will protect the unit so I would suggest you get some sort of case from somewhere. It is convenient to order it when ordering the VNA.
Boards.jpg

I had a friend print a case on a FormLab 2 SLA printer. It came out very nice.
SLACase.jpg


VNAinNewCase.jpg

Note that there are a couple of LEDs that you need to be able to see somewhat. The translucent case makes that possible without having to drill holes in the case. The red LEDs indicate battery capacity.
Lights.jpg



When I get some more time I will do a demonstration of how it can be useful around the workshop in general and rocketry in particular.
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Re: NanoVNA V2: An Inexpensive and Effective Vector Network Analyser

Postby Voyager » Fri Oct 02, 2020 9:40 pm

That’s a great write up OTT. I have the V1 model and found it very useful. However, the 3 GHz range of the V2 model makes it great value. It’s no Rohde & Schwarz, but for that price I’d forgive its shortcomings.
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Re: NanoVNA V2: An Inexpensive and Effective Vector Network Analyser

Postby strud » Sat Oct 03, 2020 8:32 am

Hi OTT, that is a great find.

I've signed up to be notified when the seller is back so I can get me one of those!

Definitely have some RF projects where that will come in handy for sure.

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Re: NanoVNA V2: An Inexpensive and Effective Vector Network Analyser

Postby OverTheTop » Sat Oct 03, 2020 11:15 am

Thanks Guys. I looked at the V1 but it doesn't have the frequency range of the V2. The V1 also uses only one RF SOC to generate the frequencies, and relies on harmonics to get the higher frequencies. The V2 is a complete redesign, and uses two separate RF SoCs (three actually, to simplify the hardware) to cover the range at fundamentals. One for below about 137MHz IIRC and the other for above.
Preliminary Block Diagram.png
Preliminary Block Diagram.png (35.84 KiB) Viewed 1309 times


Don't forget to order the case and the cal/cable kit when you order. I had great customer service from tindie. You might want to order a battery while you are waiting for the unit to arrive too.

I have seen a slightly larger 3D printed case that accepts an 18650 LiPo battery. You may want to consider that too. Runtime would be very good on that. The battery I fitted will give a couple of hours, but the 18650 would be much more.
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Re: NanoVNA V2: An Inexpensive and Effective Vector Network Analyser

Postby Voyager » Sat Oct 03, 2020 11:59 am

Yep, I'm in too! I already have the cable & calibration kit, but I'll definitely get the case with it.

My current RF project is a cylindrical patch array on a 98mm airframe for a 921 MHz tracker Tx. I hope to do the same for the GPS L-band Rx, too.
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Re: NanoVNA V2: An Inexpensive and Effective Vector Network Analyser

Postby knight » Sat Oct 03, 2020 3:00 pm

I've been toying with getting a NanoVNA for some time, just never got around to it. I might jut put an order in when he opens again in a week. How long did it take you to get it from when the order was placed?
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Re: NanoVNA V2: An Inexpensive and Effective Vector Network Analyser

Postby OverTheTop » Sat Oct 03, 2020 4:27 pm

It was seriously quick postage. Around a week I think. That was earlier in the lockdown though, now parcels can take a bit longer.
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Re: NanoVNA V2: An Inexpensive and Effective Vector Network Analyser

Postby knight » Sun Oct 25, 2020 9:42 pm

Well you convinced me and having ordered one mine turned up in just over a week (it seems it missed it's connecting plane in Singapore and had to wait for 36 hours for another one).

In the week and a bit since I received it, I've checked both my HF antennas (which were ok, a little bit inductive on one and I suspect marginally too short) and discovered that my 2m dipole for reasons best known to someone else was no where close to resonant... not quite sure what happened there, but at least I know why it wasn't working.

7MHz (40m) loaded vertical - Slightly inductive, probably got the loading coil in marginally the wrong spot:
40mAntenna.jpg
40mAntenna.jpg (88.16 KiB) Viewed 1068 times


For rocketry projects, I've got a couple of RA-02 (aka SX1278) LoRa transmitters that I plan on turning into a flight computer and ground station at some point, so this will support the development of antennas for that project.
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Re: NanoVNA V2: An Inexpensive and Effective Vector Network Analyser

Postby OverTheTop » Mon Oct 26, 2020 11:23 am

Sounds like you are getting some good use out of it :) .
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Re: NanoVNA V2: An Inexpensive and Effective Vector Network Analyser

Postby Voyager » Mon Oct 26, 2020 4:12 pm

Thanks for the original heads up OTT. Mine arrived last week and it's definitely more useful than the V1 model with the extended range! It will get a good workout shortly with my patch array.
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Re: NanoVNA V2: An Inexpensive and Effective Vector Network Analyser

Postby OverTheTop » Mon Oct 26, 2020 5:50 pm

The V2 was completely re-engineered, with the extended range provided by a set of three RF SoC devices. The original only got to the higher frequencies using harmonics from the lower frequencies. The V2 does it with VCOs on the fundamental.
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Re: NanoVNA V2: An Inexpensive and Effective Vector Network Analyser

Postby MattSR » Sat Jan 02, 2021 9:11 am

Thanks for this thread OTT, I will be joining the club with this one, as I can make good use of it for my HAM projects too.

Cheers,
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Re: NanoVNA V2: An Inexpensive and Effective Vector Network Analyser

Postby OverTheTop » Sat Jan 02, 2021 3:12 pm

No worries Matt. It has proven its worth to me a few times already. Well worth the money IMHO.
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Tuning My Telemetry Antenna Using the VNA

Postby OverTheTop » Thu Feb 18, 2021 12:27 pm

I am adding a telemetry downlink to my VTS and needed an antenna on the right frequency. The VNA allowed this to be accomplished very quickly.
5resize.jpg


For the full story on the making of this antenna, see here:
https://www.rocketryforum.com/threads/t ... na.164715/
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