Antennas for Meshtastic LoRa 868MHz SWR and RSSI
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- Опубликовано: 19 май 2024
- I tested a variety of antennas using a Nano-VNA vector network analyser and traceroute received signal levels from a Meshtastic node about 400 metres / 0.25 miles away on. Comments and suggestions are welcome. For more fun, watch my next video where I measure some "identical" antennas 🙂
There is a Facebook group which I forgot to mention is Meshtastic Brighton
The Facebook group I mentioned is Meshtastic Brighton
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A much larger Facebook group is Meshtastic UK
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Lovely video, I like your style, no nonsense, no clickbait trash, looking forward to the next one.
Thank you for your kind comment ! Those things annoy me in other peoples videos. That and music which is too loud and irrelevant...
"For those of you watching in B&W, the yellow curve is below the *BLUE* curve." Not that you would know which is the blue curve if you were watching in B&W. Love it!
Otherwise, good video.
Hehe - you spotted my joke :-)
Thank you for testing
You should re-test the Medium Plastic antenna in a 90 degree setup, you'll see the SWR go up to as far as 4 db. not sure why. I tested 4 of them and all did same thing.
I agree with you. Antennas are very sensitive to surrounding objects ! I normally avoid using the 90 degree bend function. Problem also is that on a node in a bag, the antenna SMA connector comes unscrewed far too easily !
why? because you add 4dBm of inline loss most likely, VSWR does not equal efficiency, a good dummy load will have an VSWR of 1:1, and yet 0% efficiency as a radiator.
One recommendation. Try not to disconnect the UFL/IPX socket too much. I would suggest putting an sma pigtail on the heltec and leaving we’ll be. Had a connector go intermittent today narrowed it down to wear and tear on the ipx plug. The sockets thankfully seem okay so far. The SMA at least will take more connecting and disconnecting. I’d say also having seen the heatshrinked coils on coax they are variable performance at best and often not resonant at the signal frequency. Good luck Simon with the experiments and thanks for sharing the video. 73 if that applies 👋
Thanks for the good advice. 73 !
Never heard of a sauce pan antenna!? You learn something new every day. 😉
Thank you. Your video is brilliant and so informative
Glad it was helpful!
Thanks very much for the video, I've just been doing some similar tests on a cheap outdoor antenna I bought from Ali Express. Honestly it is awful with a slight resonance at 950 even though it's sold as 868. I've spent a while trying to fix it by adding length but it's now in the bin. Best place for it by far! . That pi hut one looks good for the price. Thank you!
Glad it helped. Meshtastic is certainly rekindling enthusiasm for experimentation and home brewing. Don't put it in the bin ! Cut it open and repurpose the parts or use it for experiments like I am doing with my rubbish antennas :-)
@@fotografm only the rubbish antenna bit went in the bin 😉 I kept the mount etc. The other thing was that the supplied coax was made with aluminium wire and so is unsolderable..(I needed to solder) . So was honestly awful. It was very cheap though! I usually make my own...that's the next job.
@@neilbchilton goodness me. Aluminium wire. That is really unpractical ! I extended a USB cable and discovered the same problem...
Good video i will make one tomorrow
Have fun
I bought 2 antennas which look identical to the 'medium plas' item you have listed as best performing. I tested them on my NanoVNA-F V2 and recorded similar results albeit the peak resonant frequency varied between the two and one was at 838. For that one I nipped around 2mm off the internal wire which brought it to 866 so left it at that. Notable that if you bend it to 90deg (it provides that flexible joint) the resonant frequency changes significantly so I would advise only using it straight. I bought some cheap pigtails to connect it to my Heltec V3 which didn't fit well and damaged the socket on the board so I haven't been able to test it! Interested to see the result for the 'free stub' which is what I'm using right now and that encourages me I will see a big improvement when (if) I finally get the better antenna attached.
Buying antennas has been a real lottery for me. Some of them seem to have really slack quality control with characteristics all over the place. Also some premade cables are better than others and I don't know how reproducibly accurate my VNA is. All this adds up to a wild goose chase bit it's fun !
"for those of you watching in black and white..." I get that snooker reference. :D
LOL
The NanoVNA is a great tool for the price but it uses a sort of "cheat" by comparing your network to a set of known points (the calibration set) for any arbitrary range. Users should remember to calibrate any time they switch ranges (these can be saved). Thanks for the videos
That is a very good point. I calibrate my VNA before every test run just in case.
A video on calibrating a Nano-VNA for Meshtastic would be great 👍
well, the nano VNA is a toy compared a real VNA, it is enough to check if an antenna is badly detuned though. But the calibration is certainly not a "cheat" that is how any VNA works, it is only good for the range you calibrated it on, and calibration should always be done prior to the measurement and with the same setup, which is the most important point, that is, you use any extension cable out of the port, it must be calibrated at the end of this extension (and the cable should be compensated for), and if you use SMA to uFL then you need a calibration kit for uFL as well, because it would make zero sense to calibrate at the SMA connector and then do the mesurements with an SMA to uFL pigtail.
There is also totally no point "saving" the calibration, it should be redone each time you change the connetion setup or power off.
Anyway one point these DIY peoples really do not understand is that VSWR is only 1/3 of the picture, you can have an antenna with an extremely low VSWR and perfectly tuned, which is a terrible radiator and has very bad efficiency, which will make it worst than an mistuned antenna with high VSWR. And the only way to test correctly the efficiency of an antenna is with a proper VNA and an anechoic room, or at the very least a large shielded box.
I use a mixture of Heltec32 V3 stock antennas coiled wire in heat shrink, but not the same as yours) and a Paradar flexible rubber duck as described on Andy Kirby's video and similar to your antenna with the hinge towards the end. I found the Paradar the best in general, but sometimes the stock antenna also gives surprising results. I took SWR readings with the antennas always mounted on a small pigtail and dangling down from the VNA with my hand on the opposite side of the VNA, holding it. I found that not connecting directly to the VNA altered the resonant frequency, as did lightly holding the outside of the pigtail in different positions indicating that the feed line is part of the antenna. This effect was least pronounced for the Paradar. I'm pretty hooked by this stuff now....
Thank you for the info. I noticed that some antennas perform completely differently when hanging upside down ! There is also no groundplane of course apart from the coax feeder. Also, some antennas are manufactured as monopoles and some as dipoles or co-linear elements. It's a bit like antennas for handhelds. You can never guarantee how the user will hold the radio (if at all) and this has a huge effect on performance. I am also really hooked on Meshtastic as it reawakens that pioneering spirit of experimentation and being at the forefront of something new !
Great! Thanks for sharing the video. BTW, can you share the link where you bought the MEDIUM PLASTIC ANTENNA?
Seconding the comment on calibrating a NanoVMA for Meshtastic. Particularly the range you use for SWR...
It's all a learning curve for me.
It's taking off in UK must because all them cells out of Birmingham..
Lots of comment about those ebay Paradar aerials (I got one). Pending aVNA check first, but if bad I think I will get one from the legitimate site instead.
Exactly. It is a bit of a jungle at the moment. The only trend I can confirm is that the more money you pay for it, the more likely it is that the antenna will perform properly as expected.
Can’t you do a video about the unit you’re using when you get used to it. Please. Ty. 😊
Which unit are you referring to ?
@@fotografm the nanovna
Using a fixed antenna on the second port of the VNA, could you get a sense of the antenna gain by looking at S21? Looking at the VSWR and match only tells if the energy was delivered to the TX antenna, not how much of that energy was radiated to the RX...
That is exactly what I planned to do next. I obtained a cable of reasonable quality to connect the distant antenna to vna port 2.
mmh, no, because this is not an appropriate tool nor setup to test an antenna efficiency.
@@lo2740 Oh you are right. He should just buy an anechoic chamber for a couple million dollars so he can do far-field tests like the pros...
In the meanwhile, he can get a sense of near-field gain with a reasonable cable length. duh.
Are you sure that that antenna mounted on the wooden stand is a Supaerial? Only asking as when I searched and went to the Amazon link, the antenna it showed was that long plastic one that gave you a very poor reading.
At the moment I am not sure of anything as there seems to be a fair amount of misrepresentation with labelling and/or shipping of wrong products. The Amazon antenna I bought was coloured black on their webpage and was black when it arrived. There may be other versions however. I just ordered some more antennas that were only available in white !
@@fotografm I know where you're coming from. It's the only headache I am having over here in Portugal. I am looking for something like that one of yours on the wooden stand. I feel like taking the VNA with me to test them in the shops, but I can just imagine the faces of the shop owners lolol.
@@PortugalCarp I am surprised that walk in shops stock things like this. If so, I would definitely walk in there with my VNA and choose one that worked. Don't be shy - just do it !!! Here in the UK I only found them online so far which means you have no idea what you are buying until it arrives in the post....watch my next video where I measure some "identical" antennas 🙂
@@fotografm Thanks for the reply. Looking forwards to seeing your upcoming video.
Is that a 4.3 inch NanoVNA? Please post a link to that model.
Yes it is a 4.3 inch NanoVNA. I got it from Amazon (link below). I see that on Aliexpress they are available for around half the price if you don't mind waiting and risking that it could be a cheap fake version.
www.amazon.co.uk/gp/product/B085CFHTBM
UK: PiHut out of stock. EU alternative suppliers attract the Brexit Tax end up being £14
Deary me... ripoff Britain LOL