 the hashtags for all the socials. Hello! So from the remote stage, now comes the talk measuring antenna. Be it LTE or 3D, for all of those you need antennas. How can I adjust my antenna? What's the difference between the cables and what can I do to adjust my antenna? You won't be able to see the person. They prefer not to be shown. Apologies for any breaks. I appear to have a hiccup. So oftentimes people talk about antennas but the hiccups among us tend to take a closer look. Yeah, there are chances to use antennas, optimize them and oftentimes we might wonder what kind of antenna is it and might I use it for a different case or maybe I want to buy an antenna, a Wi-Fi antenna for example and then we want to check, well what are the promises of the seller but are the claims justified? We cannot see radio waves and so we are oftentimes kept in the dark and also when you want to build your own antenna you need to know what you're doing. So we need tools and they have been around for ages, the tools, measuring tools and others but they are quite expensive. Five, six, number five to six digit costs but the good thing is there are affordable options as well. So for example the nano vna it has a range from 50 kilohertz to three gigahertz and you can do a lot with that. It's available with SMA or N. For our software you find radius SMA is usually better but you have to check your application. There are many replicas and also fakes and so we have to be careful and those cost around 80 euro so the originals. So let's check what it looks like. So it's the small box here, a small touch screen, a few buttons two antennas, slots, these little heads for calibration and yeah some cables and with this we can play a little. How it works i will show you. So a close-up there are two ports, the S11 and S21 and S11 is very interesting indeed now and yeah on the side we have the on-off switch. There is a battery as well. I prefer connecting it to a computer when using it because then work is just more comfortable and more precise. So first of all we download the appropriate software. You can find it on github and i included a link at the end in my slides. You can just download it and just run it in case you trust it and then it starts. So this is a program window that welcomes you and first of all we have to define the range we want to measure in and every time we want to change the measuring range we have to recalibrate everything. So it makes sense to first think about what range you want to use. So now we we'll start with Wi-Fi. You have that everywhere in ASP and a laptop. It really got established in the last years. So 2.3 up to 2.8 gigahertz with 250 points. The more points you have the more detail you will have but the longer it will also take. So here it does 250 measurements. So it's a compromise if you want just an overview or if you want the detail if you want a more accurate result. So now comes the calibration. It uses the l in our calibration is for short open and load. So sol calibration. Whenever you buy such a device you should check that those caps are in there because they are quite expensive. So this thing in the middle shorts out the connector. On the left we have the open one that just protects the port from radiation and then we have the load that's on the right here the silver one. It is a bit longer and that has a connection with a defined load of 50 ohm. You just screw it in wait until it turns blue and then you have your three calibration measurements. Click apply and then you have your working levels and can check out the waveforms or the antenna. So if you are working with Wi-Fi for a while your collection starts growing of antennas and others. So these were in my box and some of you might know them or even use them. Those are the more common ones. So what can we see here often when you see antennas you see numbers 5 dbi 8 gbi we cannot see these numbers we cannot check these numbers we cannot see how the antennas radiate but we can see how well they match the frequency but that's important as well. So a low cost classic it's a router for 15 euros and that includes two of these antennas. So Wi-Fi antennas use an inverted SMR plug so you need an adapter and that should be a proper one otherwise your measurements will not be accurate. So now we see two colorful lines both for the port 11 so we see what gets reflected back and we don't want this reflection. So all the power should go via the antenna into the air not be reflected back so this is something we do not want and here we can see the damping or dampening we want a low level here and the other one is the SWR the lower this value and the closer we are to one than I say it is I can put it in a marker and I put in a marker at the zero frequency of the first channel of Wi-Fi that's 2.412 GHz and the marker 2 is in the frequency of channel 13 so that's the highest one we can use the highest one we can use and then one in the middle and now this curve doesn't tell us anything but everything is relatively nice the SWR is okay is okay but not perfect so now that we know the principle we have the 1043 it's a little better and we have improved curves so we have a signal that's not bad that's what we want and we can see theoretical differences between channel one and channel 13 and in channel six it's probably a bit better and in practice you will probably not even notice but this is just a 2.4 GHz antenna it was built for this and that's what they are doing quite well so in a dual band router it can do 2.4 GHz and 5 GHz so unfortunately we can't see the 5 GHz because our device only manages up to 3 GHz but we can check up to 2.4 GHz so and it doesn't quite work as well compared to the 1043 ones but that was just a perception and here we can see it so this is not at 1.3 something but more close to 1.6 so the perceived perception can now be underpinned with some figures and what you can see here the neighboring frequency is where the antenna doesn't really filter anymore doesn't have a filtering effect so these are two three classical antennas as used in Freifunk and I have this 25 year old access point that I found in my basement and what you can see here is a much shorter antenna but that doesn't it's not a problem you can see that the performance is quite good and you can see a clear valley in the data here as well so you can see that there is a separation here you can't fully say that what we're measuring here is the behavior on the emission side not the reception side but normally the transmitting side not the reception side but normally these two are very very much equivalent if it doesn't work that well as a transmitter it won't be a very good receiver either but we won't reach the kind of exactness that we could reach with the professional measuring device but we have a good impression another device that was quite popular in Freifunk times was the pico station 2.4 gigahertz all around transmitter so just the image here the chart that you see shows a very defined behavior very sharp drop down and if you look at the values on channel one we have about 1.1721 that is a very good value and the best spot is 121 really so that's the best antenna in the wi-fi area that I've come across it has to be said and it's a very small inconspicuous device it doesn't always have to be the 30 40 centimeters long antenna sometimes this is enough it depends on what you want to get to but these are things that we don't have to talk about at this stage we're just looking how well does it fit the frequency on which we want to speak so let's check the dual band follow-up from the same producer and again performance really drops it 2.4 gigahertz that's just because of the principle you can't have an antenna that is great at multiple frequencies okay something with the cable now because putting an antenna in with a cable is nice you can you are more flexible with a placement and yeah it looks okay but this doesn't say anything about the dampening of this small cable so it might not make a good antenna and something that is more directed and here this you can work with there's a small valley but not not a big one but i can tell you it works it still works i used it for many years and back then when d-link builds something tp link had to have a clone so yeah you have you get the image but we don't only have wi-fi that is pretty simple with one frequency but lte as well and that's a very special topic i have a simple antenna here but there are so many lte bands that the antenna has to work in and i have to say for being such a small contender it worked quite well with 1800 but also with 800 megahertz just for example but looks okay it looks quite quite nice and that's not trivial to develop such a thing and of course if you are cbr um no if you are just in radio equipment in general you will also have these and baufeng uv 5r it's supposed to work with 70 centimeters up to two meters and the antenna well with 70 centimeter wavelength it's okay two meter back down here you can't really use it and if you ever wondered why it doesn't work well now you know and we do other things as well and we have a pcb antenna and you can see it doesn't always have to be a wire it can be a pcb as well there are many advantages it's easy to produce them quite precisely and it's cheap and it's small and as you see the performance is okay but always just buying things is boring we can create we can make so this classical ground plane antenna for example and we can calculate the different lengths and there are online calculators as well but building it properly is difficult it's easier to make it a bit longer and then you measure it and shorten it accordingly okay here the swr is blue now but that that looks good so how can i use this for building an antenna i show it with a ground plane for lora and it's built exactly the same way so we have a target frequency of 868 megahertz so the values are not perfect yet but not too bad either so the sweet spot is with 753 megahertz and now we modified the antenna made it a bit shorter and the sweet spot moves up still a bit further now we are at 808 so well if you shorten it even further we get to to an area where it starts to be okay but yeah that's more an art than a science because if you keep shortening in it you can't make it any longer but of course you can always exchange the wire for a new one that's the advantage of making it yourself and yeah so it's relatively easy to make a proper antenna for a little money yourself now another bought antenna a proper one from seafaring people an ais antenna that's both for positioning but also for voice over radio and 160 161 megahertz it's great and for in the two meter band for voice over radio it's also good so you know this is a good antenna of course you can do more than just look at antennas because usually you will need a cable to the antenna that's the reason why we have two slots or two ports here the left and the right one so we need an s o a l t calibration here now we now only not only have the short open load values but also the through value so if we send something in how much reaches the end so we have this cable short cable that we use to connect it to and yeah so if we put a cable in like this we can check it i have a three meter cable with sma plugs that i built myself and yeah so here i can check if i made everything right or if i screw it up somehow and i checked at 1090 megahertz because it's relevant and yeah the values look good or you might wonder is that a good value and if i check the datasheet the cable is supposed to have a damping of 55.5 db on over 100 meters and if we do that calculate that on our length and the plugs have 0.2 db we have two so and the sum we would expect 2.1 db and that's more or less what we get because it would be bad if we measure and measure and our measurements are wrong so it's nice to have a plausibility check here such a cable rather simple we can now check different lengths but we can also check filters and filters are really exciting in the sdr area software defined radio per definition it has a huge range of the receiver where it's um receiving but if you want to select just a certain range and nothing else you will need a filter but everything else all the things around your target area can really mess up the measurements and there are two times of filters there are those bandpass filters and bandstop filters so here this is classical radio FM so if you have a radio sender next to you a radio station next to you you might not want to receive that so yeah we now create this filter send in the signal and check what comes out so the red line is interesting here and this is what passed the filter in the beginning here it dampens almost nothing then it starts working and here where it filters with at least minus 60 db that's quite usable but i would say it's a bit much shifted towards upwards we would have to check the details here i would accept to start 5 to 6 megahertz earlier but it looks quite clean you can get them everywhere you can sometimes even order them cheaply but you never know if they really work because it's a lot of components and yeah sometimes we want to know why doesn't it work so the bandpass in opposition here it only lets a certain frequency range through until you can see that in this area where it shouldn't let anything pass it has at least 50 db damping and then here it's a very small damping where it should let everything pass it's a rather broad one but that's okay because it should address two bands this is what it shouldn't look like i thought well it doesn't really work but i don't know why that i got this device and thought well let's measure it and you can see quite well here the minus 50 db that area is okay but where it should perform with 1090 megahertz we are at least at minus 18 that's unusable so i didn't know before i could just guess because of the performance now i know and basically that's it i hope it was interesting for at least a few of you maybe it's a device you could use and it brings light into the dark the software is in the github here if you want to see more grass you can enter check our wiki the ads barrier wiki if you want to talk to us we have mumble if you want to check out what we do with sdrs check our website if you have questions ask questions as there will be a breakout session as well if i can find it and yeah that's that's it yeah thank you very very much for this very interesting talk about technology very spot on with the timing and we have a few questions so there was a question about the graphs somebody would like to know the red and the blue curve what exactly they mean maybe you could explain it a little more yeah i'll go one slide back red and blue does not have fixed meaning you can just assign that up here one is red the other is blue and here in this example so i have to two ports the left sends the signal through the cable and the right port receives it and the left port here that's s11 i assigned blue and s21 i assigned red so on the red line i see what gets out what what comes out that's very interesting for checking cable because that's what goes out and what is received on the other side and the blue is what i'm sending uh what what gets received on the sending port so whatever is reflected by the cable so if i send something out sometimes the cable reflects it back and i want as little reflection as possible so whenever i check an antenna i can only check reflection then because i don't have a receiving port and i want as little reflection as possible so ideally that's zero i hope that answers the question yeah i hope so as well now the next question how would i measure a pcb antenna that is directly sorted to a tx chip it's difficult without soldering there isn't much you can do and if you then apply a cable and a plug it also falsifies the measurement so it's just difficult that's just the way it is okay someone would have liked to see a shit show of really bad antennas from ebay what's gammas and is there something you could provide well yeah i didn't want to buy bad antennas so i just grabbed what i had in my basement and even the no names that i thought would surely suck it performed almost decently so yeah okay but if someone bought it on accident maybe they can contact you and send it to you before they throw it away okay one more question could you also put two at the same antenna so two of the same antenna on the two ports i'm not certain i get the question correctly but i would say the right port cannot send the left port can send so i can only check antennas with the s11 yeah i can only check one after the other yeah so maybe that it receives the send signal no no no so we have a very small energy input and that signal will probably not be enough to be received on the other antenna yeah so the air would dampen it too much probably yeah okay then we have some time left i don't know if there is anything left well we could build a calibrated shield box but that would be a lot of work wouldn't it to make measurements yeah you can you can put in as much work as you like but then you could just buy better hardware i just like to avoid cables and avoid having a strong transmitter right next to it and then it works usually to get a feeling for what you have it's not 100 accurate it's not 100 scientifically correct but it's okay so if you compare work and effort and money input i would say it takes you 90 percent there thank you very very much also for answering the questions if there are no more questions coming in we could end this here and yeah well the audience can applaud you but only virtually if people have further questions that is the option of a breakout room the link is in the schedule and we will now continue we will continue at 5 p.m. with data ethics in the smart city oh one last minute question how can i can you find out uh the the which degree in space the s12 transmits well you can't figure that out you can't okay well thank you for the