Meshtastic Antenna Comparison

hello today I'm going to try to make a video about antennas and compare their performance on just on receive um receiving a wheat signal for mesh tastic 868 MHz and um just to show you what's happening on that band the ism band 868 MHz that's the um received Spectrum received on a outdoor antenna that's that's not resonant of that frequency at all you can see it's quite busy um here is the 869 525 where the um mesh tastic happens I've put up a little carrier on 869 MHz I'll Tell You by that in the second and then these are other signals and other users there's something around 868 um2 something that quite strong when it pops up so it's quite a busy little band here um if I force my metastic node to transmit by doing a trace rout bam there it is you can see there a strong signal signal the antenna is only a couple of meters away from this receive antenna so um that's what the uh the signal looks like this is being received using a SDR play rspdx and that is being driven by the software which is called SDR console which I find works really nicely for my purposes so I use it um so what I'm going to do is to go over to the the test bench which is over here it's actually a table I got out of the the rubbish pile where I live it works very well for my purposes and what I'm going to do is is try these comparing these different antennas to each other to measure receive signal strength I've got two different receivers this one has a nice display of dbm I don't know how accurate that is this doesn't but it works very well just to show you how well this thing can work I'll show you this one first and the transmitter which uh I can't show you cuz it's right down there at the end of the corridor door and it is a um Nano VNA um set to 869 MHz exactly with zero span so it's just putting out a carrier and has no antenna on it and because it's in a plastic box it radiates signal quite nicely a weak signal if you put an antenna on the signal is too strong for this test so anyway let's switch on this little quangang UV K5 brackets 8 which is actually tuned to 869 at the moment oops didn't want to press the transmit button it's disabled it says anyway trying to turn on the monitor there it is says listening on 869 and you and it's SSB USB and you can just hear the output tone from the signal generator which is unmodulated it's just a carrier and then this SSB demodulator of course results in the tone you can hear the uh frequency sensitivity if I put my finger on and off the exit button on the keyboard oh that that buzzing is the uh the main mesh tastic node transmitting desensitizing this receiver but you can hear the frequency very slightly which shows you that the uh the frequency can be adjusted by a few Hertz by touching the keyboard but this is a 12b radio um with the exumer software in it which works of course as we all know extremely well with that little antenna and it can receive 868 so sometimes I walk around town with this listening for burst of signal and of course when I'm trying to communicate with somebody using mesh tastic I hear my own signal and I can actually often hear the reply much weaker from the distant notes so I know that they are answering which is cheating listening to Raw mesh tastic signals anyway let's switch that one off and uh let's go over to this receiver the Mala hit or Mala height dsp2 I've just switched it on and I'm going to put this little stubby antenna on it which should oops I was just thinking about not dropping that so what did I do I dropped it another live video folks unedited there we are that's the uh you hear the tone frequency is different already because of the frequency accuracy difference between these two receivers probably neither of them is right and probably the signal generator is also not right but using the Nano na as a signal generator I thought was a a nice little idea I did have um a mini Spectrum analyzer tiny I say um and the the signal generator that's designed to be in there didn't really work the signal level was way too low and it didn't perform as I wanted it to at all so I sent it back I'm getting a new one just slightly different one anyway this is the malit dsp2 receiving that signal and if you can see the S meter here it's showing a receive signal level I'm not going to try and hold this like this the whole time I'll just tell you what it says I can barely read it anyway um so the best signal level that I'm getting because I have to move around to find the best signal level this is not easy at all holding a phone and a receiver and they're both heavy looks like minus 97 dbm but not sure let's move around one thing you do notice is you move the receiver you get some pretty big dips see that Signal's disappeared into the noise and there it comes up out of the noise and this is caused by multipath Reflections cancelling out at this point in space and the problem is of course if you're walking around mobile with a mesh tastic node then you're going to go in these dips sometimes or we put it down on a coffee table in a cafe and if you put it in a a hole as we call that in radio terms you're not going to receive anything from that particular transmitter move it couple of cenm or 1 in for those of you not watching it metric and that's enough to bring the singal one up up out of the noise so you really have to be careful with placement of uh antennas and move them around to get the best signal which you can't really do using the mesh tastic app because it doesn't have a real-time signal display like this so minus 97 dbm or minus 95 there that's probably the best signal I'm going to get so minus 95 dbm reive signal from that oops signal generator down the corridor in the flat so let's take this antenna off and put on different antenna here's a longer one this is one of the ones I modified those Chinese super long antennas that claimed enormous gain which I opened up and then found a little dipole and trimmed it to the right frequency already you can hear the signals louder using this antenna so it was minus 97 dbm before what have we got now you can't see this but I've got minus 90 of course the polarization matters if I turn it horizontal yeah drops down so the the um nanovna um Network analyzer being uses a signal generator actually generates vertically polarized signals if you stand it up in the same way that the receiver is standing up it's the polarization vertical and of course the BL plastic case helps it to radiate signals normally you'd expect absolutely nothing to be radiated from a network analyzer should be in a metal box like this heavy um machine door I'm not sure how they make it there Nice metal case here anyway um what have we got here minus 89 so the the best signal strength there looks like minus 89 dbm I can get by choosing the best point and again there should be a null over here actually the null is not so bad using this antenna little antenna was finding a null point this one actually isn't doing it at all so the performance is also better in terms of placement of the mesh tastic node um and when you're moving it a couple of inches either way for a particular distant mode this antenna will give much better results it seems that's an interesting result I didn't expect that interesting so anyway minus 89 dbm for that bigger antenna let's take it off this thing should have a a gain of 2.5 DBI according to the theory because it's a halfwave dipole inside there this thing was bought on Amazon advertised as a 5dbi antenna I think it said 5 DBI gain and when it arrived it came with the label and if you can read that there we are three DBI printed on the label so that was a bit of a mistake from the seller let's hope it was only a mistake and it was um7 which is in terms of Chinese rubbish quite a lot of money but I just wanted to buy it to test it I might send it back if I'm disappointed with it um so what is this I'm I'm can't remember the results I'm getting which is a bit stupid you can or I can skip through the video and summarize so let's try there that was - 87 oh no- 97 dbm oh dear the last antenna was getting something like - 89 or - 90 and here I'm just looking around for the best signal level and I think- 94 is the best that I hit just thereus 94 dbm is that big null there yes it is there's that null in that particular position that I had with the stubby antenna so this performance is not very good it's also not tuned to 868 I forgot where it was you have to look at my other video to find out what this is tuned to I don't think I'm going to open up this and try and Rune it don't know what's inside it either it's waterproof though allegedly that's the advantage of this normally I wouldn't put such a heavy antenna straight onto a receiver like this because of risk of damaging the connectors but hey here it is so yeah minus 94 dbm which is about 5 DBS worse than this little dipole so the uh the alleged gain and the advertised gain don't really add up not of this frequency anyway but it's quite mismatched at 869 MHz I know so it's not really an ideal antenna this one came from eBay and it's a parar antenna and I've got two other paradot antennas I think um which work really well the beam the yagi eight element works extremely well I can't test that in this little test cuz it's outside on the balcony mounted on a pole and it's all uh connected with um taped up connectors to make it rainproof cuz it's raining in Brighton every day at the moment so I can't take it off and also the other superial black outdoor antenna is also nicely mounted and and sealed with tape which I don't want to undo at the moment but next time I uh do take those antennas off the notes for testing or something then I'll make a video so here I am carefully trying not to drop this or make the receiver fall over what have we got here - 96 - 94 dbm I'm moving the antenna around slight Focus Please Mr camera thank you I tried to improve my audio because people commented it was a bit quiet on these recordings and the apps that you can you can't adjust the audio level of course on the phone video recorder on this Android who away the apps you can buy have got terrible reviews and they say they don't really work so that doesn't really work I think I saw minus 93 dbm in there somewhere there's - 93 so again it's not very good I think minus 93 I'm moving the antenna around yeah that's about the peak signal level I can getus 93 DPM um so none of these antennas are as good as the black one there which is a halfwave dipole um which reminds me I do have some more halfwave dioles I can play with or another one I mean and also I have a uh just unscrewing the antenna connection I have a another antenna let's just try those I forgot to put those on the table um so what I have over here is this antenna this came for free with a um what was it called an RTL SDR blog version 4 receiver only wanted the the dongle but the dongle only was sold out so I had to get it with the free well not free but the included antenna a few other bits and pieces like a lossy cable I didn't really want either but there we are but now the antenna is coming in useful and surprisingly enough it's actually resonant came with uh two different sets of elements telescopic elements longer ones and these are the shorter ones and when you collapse them down to the minimum size it's actually resonant around about 870 MHz by chance or maybe it's designed like that let's hope it was designed so I'm going to move this antenna around now just a simple halfwave vertical dipole with no Rome or plastic casing [Music] let's see what we get minus 92 dbm - 91 I saw in there - 90 so it's hitting minus 90 dbm so the performance is very similar to the other halfwave dipole in the the black plastic case those cost £290 each from AliExpress but you have to open them and trim the the radiating element make it longer which is not as easy as cutting bits off but I've done it with quite a lot of those antennas now and they all work the same so this is aboutus 90 dbm there may be a little bit of loss in this car cable don't know how good quality that is you can't really take it off easily to test so I think that the result of this quick experiment is that this antenna gives the best performance this gives the worst performance don't know what's in there it's too short for cinea maybe so I don't know and this one is a bit better it's not brilliant but again it has the advantage of being waterproof the parad outdoor antenna um but certainly for indoor use I would use this one a little stubby antenna works pretty well for what it is it's just a little coil of wire in here enamel copper wire like a Spring end fed um well there's other one other thing I wanted to comment on I don't know if it happens on this receiver turn up the volume but if you put your fingers on and off here the signal level doesn't change which is what you would hope because that dipole is balanced and it has like a ground of its own but if you put one of these antennas on then it's an end fed antenna with no ground element like a dipole would have is actually virtual you can mathematically um assume it's virtual and do the calculations so what it's doing is it's re relying on the receiver as the ground and oh yeah you can see that when I hold on to the shield of the plug the signal level increases and decreases so what it's saying is that it um is happy being on this this Maly receiver because it's a metal box and that's making a ground plane for it just like a ground plane antenna mounted on the roof of a car and when I touch that signal level goes down so it doesn't like having any more ground now I'm being inquisitive because I want to see what happens on this receiver let's turn that on let it start up and switch this one off so this this is the quangang U vk5 with the Exuma software for 869 MHz the squelch closed if I press that button I programmed it to keep the squelch open and the S meter doesn't mean much but you can hear what's going on that was a transmission from my mesh tastic node what I noticed earlier was when you touch this the signal level changes actually it's not getting stronger like it did earlier earlier on when I did this the signal level improved because it needed the ground of my fingers because this is not such a a good grounding case it's probably not shielded actually when I touched the keyboard the sign L goes down so you see there's a lot of variables here things that can change um but I hopefully have provided some sort of comparison between these different receivers and you might be able to perhaps influence your purchases or experimentation based on this I'm now listening at 868 decimal 062 which I've saved because this channel often has little bits of activity it'll burst packets of data of course there are none now that I want them but sometimes it's quite busy maybe in the evenings so I don't know what's using that maybe you know what's um sending packets on 86862 and sometimes it looks like a carrier that's modulated but it's not it's not just bursts but it's a fairly continuous signal which is of course not on at the moment so there we are looking forward to receiving your comments please like And subscribe the video and uh see what I do next

Channel: Simon Phillips

Views: 2,207

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Id: h80bw3-UWa0

Length: 17min 39sec (1059 seconds)

Published: Thu Feb 22 2024