How do antennas work?

g'day and welcome back to our model reviews today I'm talking antennas and most particularly antenna theory because there are so many different types of antennas you've got miss sq playing our wheel we've all seen those there's your new pagoda antenna which is supposed to you know which actually does a job even better we've got patch antennas you know well everyone's seen a patch internal these are very good zero on my ones you've got things like loaded antennas this is a loaded antenna see it's got little coil in the SA and they've obviously made that antenna shorter than it needs to be by putting a coil in it there might even be a load in cool in here I don't know so there are all sorts of different ways to make antennas and they all basically do one job they turn magnetic waves into electrical energy and I'm gonna show you how they do that let's go over to the whiteboard and have a look at some theory and welcome to the whiteboard here we are now look this is a meter the old meters had needles they move back and forth we don't have those anymore we've got LCD display so it's a bit hard to show this with an LCD display but I will do it I'll do it just for you and here are the leads from ammeter they go across and they connect up to a piece of wire and here I have a magnet media op magnet can be a you know a neodymium magnet it can even be electromagnet and what happens is these green lines here are called lines of flux magnetic lines of force and every magnet has them and they come out and actually extend out into infinity they get very weak of course but in theory they go on to infinity and if you hit something sensitive enough you could detect every magnet in the universe but we don't have anything that sensitive but anybody ever hears a magnet it's magnetic field and if we do something like this and have a magnet setting by wire absolutely nothing happens nothing happens at all because this wire is an antenna but it won't pick up a permanent magnet field antennas only work with a fluctuating magnetic field what happens is if we move this magnet this magnet is moved up and down left and right whatever then these lines of flux will actually pass through the wire as you can see if I move the magnet closer then this line of flux will cross that wire and if I move it down then this line of flux will cross the wire so when magnetic fly lines of flux intersect a conductor a piece of wire then you get a current induced in this circuit so the current will flow through the circuit depending on which way the magnet is arranged the counter flow this way you Oracle flow way and this is actually how alternators work how generators alternators where we have a spinning shaft and electricity comes out what happens is inside the alternator we've got some magnets and some coils and when the magnetic fields intersect with the coils electricity is produced and so that's the same theory as an antenna and this actually brings up something interesting completely and not related to RC but you can get Wireless phone charges now you know you just put your phone on a pad and it charges if you've got the right phone and you've got the little wireless charger how does that work well it's the same thing you've got a magnetic field or fluctuating magnetic field in the little pad and you've got a net a coil of wire in your phone and the changing magnetic field induces our current in the coil which then charges your battery you don't need wires it's it's a wireless electricity transmission and that's all that radio is it's a wireless transmission of electricity and there's all sorts of potential uses for this but the one we use most often is communications and control radio control for example in this case so let's have the switch let's go over to the whiteboard now sorry I'm at the whiteboard what am I thinking let's go to the bench and I will demonstrate this effect for you with a multimeter alright so here's a super simple experiment that you can even try at home and all you'll need is a multimeter preferably a reasonable quality one and magnet and what I'm gonna do here is I mentioned that when a magnetic a changing magnetic field intersects a conductor it creates an electrical voltage or a current of the if the conductor has current path so if you make a loop of wire and you expose it to a varying magnetic field you will get a voltage and a current induced into that piece of wire and we can take that voltage and current fit into a receiver and the piece of wire becomes around Tina but let's just look at the very basics first I've got my magnet I've got some leads here which will act as a piece of wire what I'm gonna do is just take my red lead from my multimeter here just get rid of the black one because I'm not going to use it what don't need ice do I know I'm gonna get rid of the red one get rid of the red one here we go unplug it so I know I only have one lead plugged in to my meter yeah that's gonna work well I'll show you I'm gonna put into this J key which is the milliamps and micro amps it's most sensitive range on my meter so now I just have a loop of wire that is going to be connected to the most sensitive range of my meter I'm gonna Tim I met around to micro amps it means it's going to display millionths of an amp that's a really really small amount and typically an a receiver will be quite sensitive yet to one micro volt which means it'll be able to pick up one micro volt 1 millionth of a volt of signal from the antenna will enable receive it to do its job it's all you need and most good receivers what I'm going to do now though is I'm going to move my magnet over this piece of wire so by moving the magnet I'm going to be creating a varying magnetic field just the movement of the magnet will cause the strength of the field to vary so in theory we should see something on the meter now at the moment obvious is all zeros because I'm not moving anything but let's see what happens when I start waving my magnet around look at that now it's going from negative to positive because I'm going backwards and forward so I'm going one way gives me positive the other way gives me negative sorry and just flipping back and forth like this as you can see I'm getting up to one micro amp 1.2 1.6 fact what I'll do is old I've done that this is actually got a nice doesn't have a high hold on it so can't do there but I could get probably over to micro amps here if I really tried hard waving this magnet around the wire so there we go so this is my transmitter this is my antenna it's really crude and it's really not very good because it's not tuned and this is a very low frequency obviously just like three or four hits as fast as I can move this magnet is that the frequency that I'm producing so it's really low we're talking gigahertz with our radios so yeah but you can see the magnet induces a current in the wire and the meters displaying that current that is how antennas work but let's look a bit deeper into how antennas we can what makes a good antenna and a bad antenna well welcome back to the white would now change things a bit here I've got a transmitter here this is like an old radio transmitter big master in the sky and it also creates lines of flux but when you normally draw those there's like this you know you've all seen the typical sort of radio signal radiating out like that now when that happens these this alternates because the current flowing through the antenna goes one way then the other way it's a sea permanent magnets like DC radio frequency transmissions are like AC and the frequency at which the current going in and out of the antenna changes from one way to the other is the frequency we're operating it in the case of the old transistor radios that was about between 500 kilohertz and one and a half megahertz so it wasn't very fast by modern standards and the case of error RC systems it's 2.4 gigahertz that's 2.4 billion times a second the current changes direction going into your antenna internet internet internet so that means obviously this is a very high frequency in and the higher the frequency the closer the waves are spaced together why is that why is that you asked because the speed of light is a constant now if you imagine that we have I didn't really plan to do this but let's do it anyway here is a distance and this say this is how far light travels in one second which is actually around about 300 million meters I think 300,000 kilometers a second light travel services there half hour that travels now if you had a frequency of 1 Hertz then the wave would look like this it would just be one single cycle of the current along that whole distance so the the wavelength of a 1 Hertz signal is 300 million meters 300,000 kilometers really long wavelength but let's imagine this say for example we had this multiply bit like it a gigahertz make it so that this is gonna be this one here it's gets through 1 Hertz 1 Hertz I'll use a different color pin if I can find one that's working today Brown everyone loves Brown so let's say we do one now let's say I make I'll make it a bit simpler let's do 10 Hertz so there we go look at them per color won't what was probably this say we do 10 Hertz okay two units 10 times faster so now we'll have actually 10 cycles in the same distance like this right so if we would do it in solid because it says she had to see when I do the dotted lines isn't it so I haven't done 10 but imagine that's 10 come on now you can see that the the waves have been squished because speed of light means it's always going to travel that distance and the more often it changes in one second then the closer these waves are going to be so at 10 Hertz instead of having a wavelength of it's the other pin so one Hertz listed here one hoots its equals 300,000 km/s so there's not a wavelength visit this wavelength would be 300,000 kilometers sorry yeah okay because the one second is important but threads and kilometers it's the wavelength of one Hertz 10 Hertz has a wavelength of 330 thousand kilometers and as we go up and up and up if we were to make this like 10,000 Hertz then it is we divide that by a thousand so it's going to be 30 kilometers and so on and so on until we get up to the radio frequencies they used of 2.4 gigahertz where the the length is around about 100 millimeters I think some of these I can't work it out so the higher the frequency the shorter the wavelength and it's important with antennas because we can just use any length of wire it will pick up a current will pick up a signal but it's think of the entire is a bit of a flywheel if we tune the antenna we tune it then it'll tend to want to resonate at the frequency of the incoming wave so we won't need as much energy to excite it and make it produce voltage show you what I mean jump cut this is a pendulum you know Lytton gonna get that pendulum has a natural resonant frequency if you if you set up a pendulum it will tend to just travel the same frequency it doesn't know how high it goes how much you put into it it'll go at the same frequency that's why there's all remove the old grandfather clocks had the thing that went backwards and forced the pendulum that's what gave them their accuracy because the natural resonant frequency of that movement was always the same regardless of the amount of Swing and you know so it was that it was a constant so here we have a pendulum now you know with a pendulum you can make it rock like a child swings a good example if you get a child on a swing and you push it the right time or if you're on the swing and you whoosh at the right time you can get a lot of movement up with a little bit of energy but if you push it the wrong time then it can oppose the swing and it can actually stop so if you push when the swing is way back here or the pintle is right there it'll go right up there come back and if you push again you can all the pushing Edd's together until it creates a lot of swing if you were to push as coming back this way push that way it would slow down or does she oppose the build-up so if you provide your input energy in sync with the resonant frequency of the pendulum you can get a lot of movement a lot of action for a very little amount of work that's how it works with antennas - I'll go to the antenna model here we go let's draw an antenna here is an antenna right that's an antenna it's all the simplest antenna just the link to the wire now and usually that then goes into we actually usually use a dipole like this so you have two pieces of wire and they go off like that and we used to be you'd use what's called a balanced feeder because if you can imagine this let's draw a radio wave with the green pin here comes a radio wave then you see it's gonna be half so our radio wave into sixth-year like that okay when this radio wave into sixth year we can have a positive so we have a positive being appeared here you'll actually get a negative down there and when the next phase of the wave comes through so you're gonna get a like this you're gonna have a positive and Joost here and a negative induced there so it's gonna go backwards before you get AC it's gonna be swapped flip-flopping backwards and forwards and the rate at which it flip-flops is the frequency of the radio waves so what happens there is the electrons gonna be running up and down this piece of whopping Bing Bing Bing Bing like that and if you can make your wire the right length then it'll be like the pendulum as the electricity or the you know the voltage you or currents induced in that direction if the incoming wave adds to that direction you'll get a stronger signal if however you're trying to use the frames that doesn't coincide with the resonance of this antenna you'll still get something but it will be nothing like the amount of power you get from a properly tuned antenna that's why we have antennas of a specific length like too long then it tends to pick up the lower frequencies better it has a lower reason of frequency if you have I get too short lever higher resonant frequency so it still won't ring it won't be the nice position of having the incoming signal adding to the existing amount of energy in the system so that's why we have antennas that are cut to a particular size that size varies depending on the type of antenna the most common antenna is what we call a quarter wave monopole and this is what we use for wavelength now we've all seen those because that's what you get on your 2.4 gig receive most receivers just have it a piece of water poking at the end of the cable it's a screen cable that's got a bit of wire hanging at the end so in effect I can draw that and so here is there and this goes off to our receiver that's a typical 2.4 gig receiver antenna they're not very good they're okay but they're not very good and they're not very good because a cool way of motor pole is um generally requires what we call it counterpoise account boy something something to work against because we're only going to get you know signal induced in here there's nothing in there so there's only half the you're only gonna get half the signal really but if it's cut to the right length a little resonate and you get it'll all work very nicely you know which what well enough it wouldn't use it as a transmitter antenna because it's not good enough friend transmitter antenna you'd be wasting power with a receiver you're not getting much better anyway as they micro volts just micro volts there so that's just standard quarter wave monopod there you can make that better you can and as you'll see a lot of antennas they make what they call a sleeved dipole dipole means to die means to say if two poles this is a monopole and if you the input you can do it a number of ways but the way most commonly done is that you have a little sleeve goes around the outside you send it but a tube goes around the outside and connects to the outside of your cable so now you have a sleeved that's a sleeve dipole as I can't sleep dipole that very very common in our see almost all transmitter-ready control transmitter antennas are sleeve dipoles and a lot of receivers like on the lot of the fly sky stuff has sleeve dipoles the high-tech stuff they had sleeve dipoles on some of their receivers it just gives you more sensitivity and a bit of talk about radiation patterns later but it's a bitter antenna but obviously it's heavier Spokeo it more expensive so when a quarter wave monopole will do we use it simple as it let's talk about some other antennas right so here we've got the two antennas I've already talked about the the quarter wave monopole and the quarter wave sleeve dipole and this is the dipole because got one bit up there and one but down here die to you go right so what happens like these are fine but they don't give us sometimes we want more range we want our receiver to pick up more signal we want our transmitter to broadcast more directionally how do we get around that well one of the things with vain tenors it's the more skin you've got in the game then the more signal you're going to get that's basically the more of the conductor that is going to intersect with the magnetic field that's a radio wave the more of that there is then the more energy will be absorbed from those radio waves but we have the problem we can't just make this wire longer so it captures more of the signal because then the resonant frequency be wrong it'll be too low and would get it would actually not give us any more signal so we have to have find a way to get more skin in the game without changing the reasoner frequency and the usual way to do that is have multiple antennas multiple little resonant pieces of material because each one will resonate and if you couple them connect correctly they will all add together to produce a stronger signal so instead of having one long wire could have multiple short wires and that's for example the yagi antenna this is named after the Japanese chappie who invented it and if you look at a yogi but remember the old TV the old I guess some people still use them the old terrestrial TV systems they had Yogi's that was is a a loop here this is a what we call a I look dipole and then I have a reflector at the back and then they have these little things up here and the more of those you've got the bit of the ant water the more gain the antenna has and how does that work well if you look at it you got more skin in the game you got more metal collecting the energy from the radio wave so if you space these correctly and know the right length they will add to the energy that the final piece here this piece here receives and what gets passed that will be reflected off the back one back into it so all adds together so this is how we get more gain we pick up we just capture more of the signals out there by getting more metal in the game and the downside of that is cause we end up with a directional antenna I've done a video on directional antennas and radiation patterns which I will link into the description of this one because it's quite important that you understand that concept but these antennas are probably the most likely ones you'll encounter but the yaagh you don't see many Yogi's I know team black sheep really really used a lot of Yogi's a while ago if they still do because Yogi's can be quite small I can have a lot of gain I don't know where it is but I've got a 20 disabil yeah and didn't hear on 2.4 it's about that long it does not that long it's pretty sure that's 20 decibels that's a hundred times more signal then that will pick up 100 times more signal so it's like having your transmitter broadcasting a hundred times the power whoa but it's so it'll give you you know what is it probably ten times no one point four hundred I don't know it won't give you a hundred times the range probably fourteen times the range or something like that I forget what the numbers are but yeah well maybe ten times the right happy tenth Oh who knows well I can't be bothered working it but it'll give you a lot more range but not as much as a hundred so that's the yagi antenna but these are linearly polarized and Tenace what does it mean well notice it's all straight like straight wires right so polarization I think I've done two videos well I'm not sure but I'll just I'll gloss over it now just in case I haven't all right let's talk polarization here is a typical one of these sleeve dipoles that you find on your transmitter your fpv transmitter your receivers sometimes or in your 2.4 gig system that's you know this typical rubber ducky thing we've all we've all got thousands of these things because you get them and you don't use them on the fpv equipment but normally there we go we've got two antennas right so this signal from this one travels through the ether it's that one simple isn't it easy couldn't be simpler so could it and if we look at that and we turn around you can see that these antennas when they're lined up they overlap a lot you can see that you know there's obviously you can line them up so they completely overlap so there's a good that the signal that leaves this one hits that one and induces quite a bit of signal so you get a good coupling between these antennas that's great but what happens if you do this well now look look at the area of intersection there between the vertical and the horizontal antenna it's really really small I'll draw it on the board here so let's say we've got one like this and we've got one like that right so the actual in this say we've got another one over here like this now if we look at that this area here maps directly onto that area so we get maximum transfer of signal the signal will transfer through because the wave will leave there and hit that and yes great however with this set up there's only a minimum amount of intersection and this area here is the only bit that they share in terms of their alignment now if we do this yeah and remember this is just the outside inside it's much much thinner so when we do that we lose 20 decibels of signal there's to say all this area here and here and here and here is wasted we end up with with basically a hundredth of the signal that we would otherwise get so if you have you two antennas lined up like that and you get a a signal of say X if you do that you get 100th of X because this just can't pick up a signal it's in the wrong plane that's the problem with linear polarization it's it's a it's you know very very angle dependent and that means if you're flying it you've got you antenna here on you if pv goggles perhaps and you're flying away in a plane you do a bank well where's your video gone because suddenly 100th for signal it's like being much much further away not a good look that's why we came up with circularly polarized antenna that's why one of the applications of circular polarized antennas they allow us to produce a wave which actually if we look at the normal transmission from a linear antenna I will draw this for you okay here is our linear antenna it from our it sets from our radio control transmitter right and here is a linear linear antenna on our receiver then it goes like this it goes like that there you go easy peasy isn't it it doesn't go this way if we would look down on this it's still a plan view of this let's take a look at say we're looking down from the top needs a sticks and I transmit and here's their receiver with its antenna okay it's going this way it's not going sideways so there's no this way it would look like this would be because we're only looking down on this waveform there's no horizontal component to this transmission so what happens then is what if our airplane banks and our receiver is looking like this so silly our airplanes banked over so again know we have our because we've got the transmitter portion like that receive a portion like that well suddenly this isn't really seeing anything because you can't see a wave they can you because you're looking down on it's the wrong polarization so we get very little signal this explains why most receivers have two antennas why because what you can do is obviously you have one that's going straight up and another one that comes out at 90 degrees so if we look at it this way there's the one that goes straight up this is one that goes it at 90 degrees so even if we Bank over one of the antennas is going to be receiving the right thing so this store onto it with a built with my felt pens do some juggling here here we go here is our two antennas at 90 degrees here we go here is that transmitter antenna as they are playing banks and this antenna starts to pick up listen this signal this one picks up more and more you can see because it's lining up so that's why we have two antennas that's why that always we should always mount them at 90 degrees so that you've always got one in the game even if you're completely 90 degree Bank that's why you do it so but this is a really cumbersome way to do it because linear polarization yeah why don't we just come up with a signal that exists in both the horizontal and the vertical wouldn't it be easier or yes well it's not easier but that's the best way to do it in many cases and we do that and you'll start recognizing what I'm going to put on the board now and that's done most often by way of a soonly on rfp big year Ice Cube playing a wheel which is you know what they look like um my drawing is crap I'm sorry but it's a scoop on a wheel and if we look at the the way this transmits instead of having a signal like this it actually sends a corkscrew a circularly polarized signal and that exists both in the horizontal and vertical and every other plane so when you have another antenna over here can we see that on the board we can that's great when we have another one of these scooped lane of wheels over here it doesn't matter what the relationship is between those two antennas because this is spiraling it's always going to be picking up the signal unless it's spiraling the wrong way because we still have polarization even though we have horizontal and vertical x' we have a left hand or it's like a screw thread it can be left-hand thread or right in through it as long as this is left-handed that's left hand or this is right hand and that's right hand they'll work fine at any angles but if you make the wrong thread then you get nothing it's like having these crossed because if your thread is incompatible then you know once again you're only getting a small amount of contact because instead of the the the receive you know this intended mission with this the receiver is actually trying to do this go the other way and so you get very little contact between the antenna and the coming radio signals he get very little signal and you get crappy reception and that's with this way you want to make sure you have the same polarization on each end but those the wrote was a circular polarized antennas but what do you want what do you do if you want gain from a circular polarized antenna because obviously hmm how do you make that or produce an antenna that has gained not with a linear antenna but a circular one you can't use a yogi because Yogi's only got the sticks it won't pick up very well a circularly polarized signal it will pick it up but not as well as a properly designed circularly polarized antenna with gain so let's go and have a look at what that might look like and again you've all seen these because many of you will have used them we have a reflector and we have a coil of wire and it's pretty easy to see how that puts more metal in the game what happens here is as the wave comes along and it hits there it's fine then it goes up in the next one it's there and there and because of the length of this wire and the length of the radio wave each wave adds as it goes through this coil adds to the strength of the signal so you get a compounding effect like pushing that pendulum at just the right time so we get more and more and more gain and out you go so the longer the intent of the more turns on it then the more gain you get and you might think what about resonance well hey you've got resonance you've got like a little loopy every watt as long as that loop the loop from say this point here to the matching point on the next turn is right as long as that distance there is correct then you get resonance oh so that's why the spacing of the turns is very important and also the diameter because as other factors involved as well but basically that's how it works it's hey yeah your face that's how your I gain antenna with a circular polarization but of course there is one more type of antenna it's not really an antenna it's an extension to an antenna that can be used with circular or horizontal polarization but we very really use them although if you want to go a long long long long long way then this is what you want and it is an antenna it doesn't matter what sort of antenna it can be a sleeve dipole it can be a balanced dipole it can be a scoop planar antenna can be anything you like but you want to have an antenna which can draw a circle because it can be any kind of antenna right there and that goes off to your receiver down there all right and what you do is really quite simple is you put a great big hunking dish on here not there so that you're capturing all this area here of incoming signal whoo and you're reflecting it onto that antenna comes in and it bounces onto the like like a um well like a solar concentrator or anything out there like a headlight beam what it's doing is its collecting all that radiofrequency energy and directing it directly onto the antenna and the great thing about dishes is the size of the dish doesn't matter it's the antenna that's important so you can use one dish for many many differences as long you have different antennas at the focal point and we've seen it satellite dish obvious examples satellite dish satellites don't broadcast a whole lot of power so if you watching satellite television you're way down here on the earth 20,000 miles of Sipan space there's a satellite and it doesn't broadcast a lot of power but that's because there's so much gain from these parabolic dish antennas we can pull that tiny little signal out of the ether and use it to run it or use it to deliver a signal to a television it's fantastic because these can have depending on the size massive gains you see the big radio telescopes you know the dishes that point out into space for detecting pulsars and quasars and things they have obviously they've got have a fantastic amount of gain because some of those signals have traveled thousands or millions or even billions of light-years to get to that antenna so you've got to collect an awful lot of them before you can even detect them so you have massive great dish now obviously dishes for us you know on the hobby pretty impractical you know gonna have a dish on your transmitter or a dinner on your model now it's not gonna work because they're very directional is like a spotlight beam you know if you get just a little bit of you know it's gone you know because the signal will no longer be captured it'll be pointed out somewhere else so you've got to have very directional good tracking with a dish if you intend to use a dish so we don't usually use them but it's a if you wanted to do very long-range fpv this is what you would use because you can build yourself a nice big dish and put your antenna in the middle and you could get you know 30 decibels of gain that's a thousand times more signaled in just the antenna on its own whoo-hoo that's they'll take your own way even on a few hundred milli watts so that's but this is antenna theory this is hope I've explained a little bit about antenna theory as I say key factors are you got to have or a lot of metal in the game a lot of conductor in the game for them to get a lot of signal but I have spoken about radiation patterns because as I mentioned here this is very directional and there's no free lunches in the antenna business if you want a lot of gain you have to sacrifice something and what you usually sacrifices directionality now or on omnidirectional tea let me just draw a picture for you as I say there is a video you should watch which I've linked in the description of this but if you're too lazy I will give you our brief this whiteboard is awful means lost this one portability I hope you can see this but um if we have our little here's our little sleeve dipole that we've talked about before guys often here's our transmit they said we put a transmitter on it typical radio control transmitter if we were to look at what happens you know we had a little meter we can measure the strength of the radio signal coming out of this it would look something like this it's kind of like a big donut make you move cross-section to donut there's a big circle out there in a circle like there's a hole through the middle that's as close as we usually get to omnidirectional or drips the iso direction which is drifting the same strength in all directions it's as close as we can get in the real world and what happens is when you get a high gain take the trainers for example a lot of people have taken the 3d support to point to disability no the little one like that and replaced it with a five disability well how do they get the extra disability a what it means is that this antenna is usually slightly differently designed and it produces sometimes they have a little coil in here and all sorts of clever little things because you can actually use a longer antenna and put a little coil and I could look shorter or a little may use loading to make it look shorter and things like that it's way over that you know beyond this video to explain all it but what they do is they effectively change the shape of this what called the radiation pattern and instead of doing like that the radiation pattern looks a bit flatter like this so it's the same amount of power your transmitter is not putting out any more power but it's it's sending in a different direction some odd so if you're looking at ultimate range with the to disability no this is the maximum range you can get right with the five disability inner you can get that range your signal is pushed out the sides more the bad thing is si no free lunches if you're not if you have your antenna pointed in the wrong direction then for example so if you're flying out here if your planes up here like so Jesus a nice plane if your planes up there like that then if you're using the regular antenna then it'll give you what you this so it's down here here's your plane right with the regular antenna even though it's only 2 decibels you're gonna have control but if you're using the 5 disability antenna and your int and the planes in the wrong place well actually you're not gonna have control keys just signal alone you go a bit far you get more range with the low gain antenna than the high gain antenna if you're in the no higher elevation as it's called so you're not directly at the side so this hole at the top where there's virtually no signal is much bigger with a high gain antenna for using these sleeves I'll say ya gotta be aware there sa no free lunch is only the same ear amount of power it's just distributed differently with a high gain antenna and with a yogi I'll just do a quick view of the yogi to show you have it might work if my board on a race arthas's awful a man you fix this see I see people have said you some wd-40 I'll try it let's draw our yagi antenna leave what's called radiation patterns and they've all done in a lab with in an anechoic chamber and all sorts of clever stuff right so there's yagi antenna goes off to our transmitter we were going to do that and in the old days and people did use Yogi's think may not help this game back a long time ago when you probably for most of you were born may not health flew to 27,000 feet I think with a model aircraft antic because we only had the old long while iron and so forth he used the yagi antenna on his transmitter to get that sort of range because it wouldn't give it normally so use the yagi antenna it was a great big thing because 27 megahertz is like really big antennas cause the wavelengths are so long and the frequency is low right so if we were to draw that radiation pattern with a yagi it's going to look something like this and they'll also be some little bits out here you get we call side lobes don't have to worry too much about those but you can see that if you are pointing your antenna at the mobile you can go a long long way to go that far however if you're flying out the side you might only be able to go this far so you've sacrificed that range of you just squeeze their balloon differently in affecting the video or link to I use the balloon oh no I use the balloon to demonstrate the fact that it's just like taking a balloon and squeezing it into a long sausage shape or having nice and round depending on which one day there you go that's enough rent in a theory I'm bored now I'm sure most of you have gone to sleep long ago and have got better things to do with your lives and watch me talking about bored but that's it that's antenna theory so in respect to the long-range systems you can see how important antennas are because you know it's the little changes if it's not resonant then you'll get very poor efficiency and if it's a directional antenna it's put in the wrong direction you're gonna get very poor results and if it doesn't have enough skin in the game then you're also gonna get poor results because as I said on the free sky 9 or is it long right system the receiver antenna it's long enough but they've bent it round and the bending round at the end but basically means that the bit of signal that's picked up on one side is gonna counter the bit on the other side it'll still be resonant so that's good but it won't be the most optimal antenna in terms of its sensitivity okay but what we might do is just once I've tested the frsky system I will make my own antennas up and we'll try them out we'll see how they go because pi you know it's it's always good to experiment and learn about stuff and so I'm sure that we can make some pretty good sleeve dipoles or whatever because that's what the crossbar uses some sleeve dye pops and they'll get much better results in it little flimsy sort of film antenna with the thing on it whatever and we can also look at transmitter antennas and make up perhaps a a sleeve dipole for the transmitter that they're sending it apparently our sending a new a new antenna ooh lucky lucky so when that arrives we'll use that and see how go so I'm not going to test it with the other antenna because obviously that would just potentially damage the module anyway questions comments in the usual place and I thank you for watching and now I've got so much more to do it's so hot I took my GOC off because it's getting warm springs on the way in the sudden hemisphere thanks for watching bye for now you

Channel: RCModelReviews

Views: 561,850

Rating: 4.8715944 out of 5

Keywords: radio control, RC, transmitter, receiver, antenna, patch, helical, skew planar, cloverleaf, dipole, sleeved, theory

Id: fSoXIqBlg9M

Length: 35min 30sec (2130 seconds)

Published: Tue Aug 29 2017

Reddit Comments

[u/jwoft]

If you really want to learn about antennas: https://youtu.be/gUZ4irLY-E4

[u/jwoft]

This guy is cool for RC stuff but knows nothing about RF; especially to be attempting a "how [it] works" video.