Quantcast

NanoVNA V2: An Inexpensive and Effective Vector Network Analyser

The Rocketry Forum

Help Support The Rocketry Forum:

OverTheTop

Well-Known Member
TRF Supporter
Joined
Jul 10, 2007
Messages
4,310
Reaction score
1,516
Location
Melbourne Australia
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 $86, 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 $7200. We have another bench unit that will cost you $42k new, and we have a third one that is even more expensive. So, to get something that is reasonable for around $86 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?
Preliminary Block Diagram.png


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.

Disclosure: I am posting this on both the US and Australian rocketry forums. This is sometimes considered bad manners, but I think everyone needs to find out about this device. Very useful if you do anything with RF.
 
Last edited:

jderimig

Sponsor
TRF Sponsor
Joined
Jan 23, 2009
Messages
3,160
Reaction score
566
Very cool. Can this be used to effectively build and tune a pad antenna for ground station use at 900Mhz?
 

OverTheTop

Well-Known Member
TRF Supporter
Joined
Jul 10, 2007
Messages
4,310
Reaction score
1,516
Location
Melbourne Australia
Yep. It will give you a dip at the resonance frequency. This is probably where mine will get most use. It will also measure performance if you are off resonance to enable you to estimate dB loss for link budget impact. It will direct read SWR on the Smith chart.
 

OverTheTop

Well-Known Member
TRF Supporter
Joined
Jul 10, 2007
Messages
4,310
Reaction score
1,516
Location
Melbourne Australia
Very cool. Can this be used to effectively build and tune a pad antenna for ground station use at 900Mhz?
Here is an example of checking an antenna. This is with the VNA exactly as supplied, out of the box. It comes preloaded and set to scan 100-900MHz. I connected a 435MIz antenna I had laying around. Immediately the dip was visible in the Log Magnitude plot. The cursors were moved to the closest point using the buttons and then the numbers read.
LogMag.jpg

So 436MHz was the closest I could get to the dip with the frequency span set at 100-900MHz. Note that the dip occurs because power is coupled to the air (aka transmitted by the antenna), thus leaving a smaller amount to be measured. If you want to know the frequency more accurately you can set the span to values around the area of interest (there is a limited number of sample points in the scan band), recalibrate (or recall a previously stored cal) and rescan for more resolution at the relevant frequencies. The other markers show the location on the Smith chart (green) and phase plot (pink). The distance the green marker is from the origin of the Smith chart indicates the SWR and it can be calculated from this chart.

FYI the antenna is at resonance when the phase plot is on the centre (zero degrees) line of that axis. Look for the pink arrow on the left.

Another alternative is to change the Log magnitude plot to a direct-reading SWR plot if that is what you are interested in.
SWR.jpg

The value of SWR at the relevant frequency is simply read (1.4 in this case) from the parameters at the top of the screen when you have the marker set in the required location.

Simples!
 
Last edited:

jderimig

Sponsor
TRF Sponsor
Joined
Jan 23, 2009
Messages
3,160
Reaction score
566
Cool I remember doing this with a tube grid dip meter back in the day....

Here is an example of checking an antenna. This is with the VNA exactly as supplied, out of the box. It comes preloaded and set to scan 100-900MHz. I connected a 435MIz antenna I had laying around. Immediately the dip was visible in the Log Magnitude plot. The cursors were moved to the closest point using the buttons and then the numbers read.
View attachment 433752
So 436MHz was the closest I could get to the dip with the frequency span set at 100-900MHz. Note that the dip occurs because power is coupled to the air (aka transmitted by the antenna), thus leaving a smaller amount to be measured. If you want to know the frequency more accurately you can set the span to values around the area of interest (there is a limited number of sample points in the scan band), recalibrate (or recall a previously stored cal) and rescan for more resolution at the relevant frequencies. The other markers show the location on the Smith chart (green) and phase plot (pink). The distance the green marker is from the origin of the Smith chart indicates the SWR and it can be calculated from this chart.

FYI the antenna is at resonance when the phase plot is on the centre (zero degrees) line of that axis. Look for the pink arrow on the left.

Another alternative is to change the Log magnitude plot to a direct-reading SWR plot if that is what you are interested in.
View attachment 433753
The value of SWR at the relevant frequency is simply read (1.4 in this case) from the parameters at the top of the screen when you have the marker set in the required location.

Simples!
 

RocketDestroyer

Well-Known Member
Joined
Jul 31, 2014
Messages
278
Reaction score
58
I really like mine. It is somewhat limited in dynamic range so there are some measurements that the nano can't do. I have used it for tuning pre-amplifiers and tuning antennas and it works great for that.

I ended up spending far more on coax adapters than the vna.

You can also connect it to a PC via the USB port and run it with the supplied software. The software allows you to save more settings and name them which is helpful. You can also increase the number of points in the display using the PC software for a cleaner (also slower) display. Here is a screenshot of a pre-amp that I tuned using my nanovna. Note that an attenuator of approximately the same loss as the gain of the pre-amp was required to prevent overload of the vna input.

Flat 432MHz Preamp.png
 

OverTheTop

Well-Known Member
TRF Supporter
Joined
Jul 10, 2007
Messages
4,310
Reaction score
1,516
Location
Melbourne Australia
Cool I remember doing this with a tube grid dip meter back in the day....
It seems to be the modern meeting of the GDO (grid or gate) and has a lot more versatility.

I ended up spending far more on coax adapters than the vna.
Definitely. If just looking at SMA stuff it isn't too bad these days. If you want cal kits for other connectors then that is a whole new expense report.
 

XrayLizard

Well-Known Member
Joined
Jul 5, 2011
Messages
594
Reaction score
163
Location
Van Alstyne, Tx.
I really like mine. It is somewhat limited in dynamic range so there are some measurements that the nano can't do. I have used it for tuning pre-amplifiers and tuning antennas and it works great for that.

I ended up spending far more on coax adapters than the vna.

You can also connect it to a PC via the USB port and run it with the supplied software. The software allows you to save more settings and name them which is helpful. You can also increase the number of points in the display using the PC software for a cleaner (also slower) display. Here is a screenshot of a pre-amp that I tuned using my nanovna. Note that an attenuator of approximately the same loss as the gain of the pre-amp was required to prevent overload of the vna input.

View attachment 433834
For the price and convenience.. it would seem to beat all the other options for Antenna tuning.
Have you noticed any problems with the measurements due to the Antenna picking up other signals from the Air?
 

RocketDestroyer

Well-Known Member
Joined
Jul 31, 2014
Messages
278
Reaction score
58
For the price and convenience.. it would seem to beat all the other options for Antenna tuning.
Have you noticed any problems with the measurements due to the Antenna picking up other signals from the Air?
I've heard of users with this issue though I haven't experienced the problem.

The vertical scale is user selectable, 10 dB per division is the default value.
 

OverTheTop

Well-Known Member
TRF Supporter
Joined
Jul 10, 2007
Messages
4,310
Reaction score
1,516
Location
Melbourne Australia
Have you noticed any problems with the measurements due to the Antenna picking up other signals from the Air?
Have not used it much so have not noticed that problem. Only a problem when testing antennas ;). I guess if it is a problem I will cart it into one of the EMC chambers at work :).

The vertical scale is user selectable, 10 dB per division is the default value.
Thought it might be. The firmware in it seems fairly well-written.
 

ecarson

Well-Known Member
Joined
Mar 21, 2017
Messages
102
Reaction score
0
The president of the local amateur radio club was extolling the value of these back in June over a series of three emails to the membership. I had not seen before, that he had sent out anything but notifications on testing sessions for tickets, and general rule changes. I gathered that this unit had piqued his interest to a large degree, and he is not one to be impressed by the latest technical gadgetry. Bang for the buck was his main amazement here.

He did make note that the unit had better utility below 433 MHz, and did not express confidence that it would have the same value in the 433 to 915 MHz areas. I sort of put it in the back of my mind at that point. However, now it seems that there is useful function in this range of frequencies. I will probably spring for the larger 4.3" display unit here in the next few weeks.
 

OverTheTop

Well-Known Member
TRF Supporter
Joined
Jul 10, 2007
Messages
4,310
Reaction score
1,516
Location
Melbourne Australia
Keep in mind that he may have had the original version. The V2 is a much nicer unit, especially at the higher frequencies.

Personally I thought the V1 would have been a bit marginal for me, but purchasing the V2 was a no hesitation no-brainer.
 

Latest posts

Top