Meshtastic Antenna Tuning with a cheap VNA (Vector Network Analyser) NanoVNA V2

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5 ай бұрын

I am super pleased to be able to tune my antennas now! Being able to verify your designs and even better - verify the quality of 3rd party antennas is great for selecting optimal performance in meshtastic and other SDR applications.
According to the listing this is the specification of the VNA:
NanoVNA-F V2 Antenna Analyzer
4.3inch NanoVNA V2 Vector Network Analyzer
3G Upgraded Version
NanoVNA with 5000mAh
Measuring S-Parameter Voltage SWR Phase Delay Smith Chart
Apparently there is a version that jumps up to 6ghz, that is double the price. Could be useful if you need that range.
I am going to have a lot of fun trying all manner of designs now!
Amazon has these, it is where I got this unit:
Amazon UK: amzn.to/3SENnMk
Amazon USA: amzn.to/49a4ATX
If you would like to buy me a coffee or support the channel you can do so via Patreon at / backofficeshow
I do have some bits and pieces on my web store at backofficeshow.com
Please note: As an Amazon Associate I earn from qualifying purchases. As such links to Amazon products within this video may fall under this. Thanks to all of you who use these links and help support the channel - you are fantastic!
Thanks you lovely people, and keep on tinkering!

Пікірлер: 18

@jester6856 Ай бұрын

Thanks Andrew, ive got one of these devices, its an older one and ive struggled to work it.... You have just shown me how to use it now. Brilliant 👍

@tubosolinas Ай бұрын

Since the (SMA->ipex) feeder plays a role in the setup and the monopole antenna is ground plane dependent,use a SMA->ipex adapter attached to S11 port,plug the feeder there and calibrate the VNA at the SMA end of the feeder.Then attach the antenna there to tune it.For 868 Mhz a 1mm enamel copper wire with 9 turns winded in a 3.5mm drill did the job.Also the distance of the first coil from where the sma ground ends is important and it's 9mm

@Roskellan 5 ай бұрын

The standing wave ratio (SWR), the ratio of the reflected power in relation to what is going out. If half of what you sent was reflected that would be a SWR of around 6 which is appalling, reflected power of around 10% would be a SWR better than 2 which would be acceptable in most cases. SWR can also be expressed as a Log in dB (as a Return Loss), A Return Loss of 10dB corresponding to an SWR below 2 and a return loss of 3dB correspond to an SWR around 6, or 50% of the power being reflected. Reflections occur when the characteristic impedance of the source device differs from the load (in your case the Aerial). Radio devices tends to have a characteristic impedance of either 50ohm or 75ohm in most cases (not all). Standing waves can blow up your transmitter because 1/ the power that should be going to the load (Aerial) must be absorbed by the source and 2/ that standing wave can produce high voltages at the transmit output when the transistors generating the power are basically current devices not accustomed to high voltages. The Short and Open circuit is used to calibrate your device, these conditions are effective worst case. The Termination is as close as possible a perfect match (should be a dot in the middle of your Smith Chart) and your device will give you a reading for it at good as it is capable. You will not make a measurement for SWR/ Return Loss better than that Termination. The Smith Chart is a little beyond this video but basically represents the impedance of your load showing its real and imaginary components. The real being resistance, and the imaginary relating to capacitance and inductance. Looking at your aerial, then the closer the trace to the center of the graph the better (the marker 1 being the frequency you earmarked with the higher and lower range of frequencies you are scanning represented by the rest of the line), the center of the smith chart representing the characteristic impedance of your source. Just a Radio Amateur guy shouting at the screen :-) A career in SatComs helped as well. The numbers Z=x+jy are J notation which is the Rectangular form to represent a complex impedance. As an Angle and a Magnitude being the other way (Polar form). Looking at, calculation, and manipulating impedance's/ matching using a Smith Chart is by far the easiest way to accomplish, this though when you are learning about Smith Chart's you would be forgiven not to think so 🙂

@joostluyten_ON3JT 5 ай бұрын

Rule of thumb : if the SWR dip shows up on a higher frequency , then the antenna is too short. In this case you had to try lenghten the antenna. But nice to see you gain knowledge 🙂 (ignore my comment, hadn't watched the whole video yet).

@backofficeshow 5 ай бұрын

I always appreciate a comment. Thank you for leaving one. I like that you edited it, it's like playing along at home 😄 I'm considering designing an external antenna for this setup. I'm curious as to how to tune it once mounted. I figure I'll cross that bridge when I come to it

@nicknackthenoo 5 ай бұрын

It's not just the SWR, you have to keep an eye on the impedance. Yours was at 28ohms, so matched a bit wrong.

@iainmcculloch5807 5 ай бұрын

Consider updating the firmware on your NanoVNA. There are a bunch of KZbin videos that will show you the process. Then install the PC software. Once you're connected to the PC the software will allow you to capture and compare results.

@Aleks-xl5rn 2 ай бұрын

Tuning only the antenna does not make sense, since the feeder has an additional influence. Specifically on the Heltec Lora Tracker board, this short feeder shifts the frequency with the lowest SWR above 900 MHz. Moreover, these distortions in the radio path also depend on the bending of the feeder. When operating at a frequency of 868 MHz, the range of the device did not exceed 500 meters. When I resoldered the board and got rid of the feeder, the communication range in the forest was already 10 km.