Right!? I was suddenly really excited to learn! It helps that the video then delivers actual no BS Lear ing content, but the orchestra definitely got me ready to learn.
Thank you Royal Canadian Air Force for creating such an informative and aesthetically pleasing video. Coming from a US Marine decades later, this presentation helped me understand the fundamentals of wave propagation.
Even today, October 2024, this is a very educational and well presented video. No fancy graphics or animation. Every EE student should view this video!
For weeks I've been looking for a video describing WHY half wavelength is SOOOO important in every conductor carrying a varying current. All videos I could find described the standing wave you create at the half wavelength, but failed to describe WHY it radiates that specific frequency. This video does the simple and yet very effective way of doing just that! Thank you to the uploader of this video!
@@artie5172 To make the most efficient and simplest use of an antenna of any length, you want to push and pull the electrons along the full length of the antenna. To do this you’ll be switching the voltage from high (to pull them) to low (to push) whenever the electrons reach the close end of the antenna to the voltage source, and from low to high when they reach the far end. If you waited for the electrons to do this you would have a wave length that is double the length of the antenna (while on the antenna you get the first magnetic peak in one direction but not the comeback peak with the reverse curl [negative sine wave] until the electrons are on their way back. You often want a shorter wavelength and can do this by switching from low to high voltage (push to pull) at 1/3 the length of the antenna and swithching back at 2/3rds so when the electrons reach the end you’re in the same position to switch from push to pull. You can actually add any arbitrary number of full wavelengths after you add the one half wavelength switch. So you could switch at 1/5 of 1/7 and add 2 or 3 full wavelengths after respectively. You’re still in the efficient position of going from push to pull when they finally reach the end of the antenna.
the simple dipole (basic antenna) radiates at lambda/2 frequency since it's in half period of a sinusoid that you can see at least 1 "back and forth flow" of the electrons, therefore in half the period (half the wavelength) you can send a high quality signal
There's a far better, and even _older_ visualization at: "Radio Antenna Fundumentals Part 1 1947" , RUclips (Fundumentals*) Don't worry about the preliminary part. 16;28 will make the whole business of E and H field propagation crystal-clear, because of the particular visual viewpoint it gives. After seeing that, then I come back to the present video at 5:13 and can now see the point of view they are presenting. ________ *the youtuber's spelling, not the Air Force's
Good explanation connecting the standing waves of current and voltage to the strength of the magnetic and electric fields that are produced by them, respectively. And an excellent description of how the radiation pattern is sketched by first measuring the field strengths at points away from the antenna.
I spent a couple of weeks with headaches reading various textbooks about this until it all sunk in. This makes it perfectly clear in 12 minutes and 25 seconds, (with the exception of the voltage/current phase relationship of the radiated signal.) The only thing I should point out is something that I originally confused myself about from seeing all those sine waves. The field doesn't actually have the 'shape' of a sine wave. The sine only represents the intensity of the energy and its field polarity reversal. It actually physically 'looks' more like like fluctuating soundwave pressures, (if you can imagine them with 2 phases and a polarity reversal.) Recall that electromagnetic waves have wave/particle duality, so they can also be pictured as a stream of photons of fluctuating density. Good luck with that bit, but you get my point. :)
I think you're wrong about this. Heinrich Hertz showed in the 1880s that radio waves are indeed 2 dimensional waves (transverse waves). Yes this may seem weird when you are forming a mental picture, but it is demonstrably true, and antennas depend upon this 2D physicality. Sound waves are longitudinal waves. They are indeed 3 dimensional.
Yeah I was ALWAYS confused with the sines regarding audio and em waves... The audio I understood by watching shockwaves. So I wanted to imagine EM waves the same. But I don't get this 90 degree between waves. I dont really understand these waves. I feel like I understand magnetic and electric field, but not a wave of them.
In the mid-70's I used this as a training film (it was old, scratched 16mm celluloid film) when I was a USAF military adviser to the Imperial Iranian Air Force. Yes, Iran was an American ally at the time and the Shah was still on the Peacock Throne. So glad to find it online. For those who think this is crude compared to what you can create with today's technology, it was animated by hand, one frame at a time, just like Walt created Mickey in 1928.
Deusdat - I just received an email where you explained the incongruence regarding the phase of the electric and magnetic field, but it doesn't appear here. But it really does explain it - great thinking, thank you so much. I should have tried to think it through myself - but it needs to be here, so I'm going to copy and paste it from my email: Deusdat replied: My explanation: In fact, the accumulation of electrons at one end of the dipole is caused by the external voltage applied by an electronic amplifier. So it's this electric field that causes the crowding of the electrons, not the opposite. The current produced by these electrons is maximum at the beginning of their flow - and so is the magnetic field! Gradually the accumulation of electrons polarizes the dipole creating a secondary electric field that opposes the initial one. So there is a point when the total electric field is cancelled and the electron accumulation reaches its peak. The current is now zero - and the magnetic field is also zero. Conclusion: both fields are actually in phase, contrary to what is depicted in the video! The phase difference appears between the magnetic field and the polarization of the dipole (the secondary field), not the total electric field. Very well done, dude or dudette, as the case my be!
When people where forced to plan and draw animations by hand, they really needed to be creative and had the time to conceive such intuitive representations of highly abstract concepts. There are few modern hack-together-the-easiest-animation-your-software-enables-you-to videos that are as informative as this one.
4:42-4:52 Shows the E field and the H field is 90 degrees out of phase but at 5:54-6:00 when we combine the component of E and H fields together, why both fields are in phase?
Big flaw: when describing the dipole behavior, H and E are in time quadrature (H is max when E is zero). Later on, when describing the electromagnetic wave, suddenly E and H are in phase. This should have been explained...
Very well said! This is the part that always confuses me, and prevents me from understanding antennas. I've yet to find a good explanation on RUclips. I get that the fields at the antenna are "near field", and the propagating part is "far field", the latter propagating energy independent of the device that launched it. But how does it go from space quadrature to space in-phase?
Good observation. The exposition in this video is clearly simplified. In the dipole behaviour, what is shown is only the reactive part of the field, which dominates in the vicinity of the antenna, being the dipole a resonant (reactive) structure. The energy of this field is stored near the antenna and does not propagate. Thus, E and H field are in quadrature. But there is also another contribution, the radiation field, which is smaller but propagates far from the antenna, in which the E and H fields are in phase. If you're familiar with AC circuits, that's exactly the same with voltage and current on a load.
watch it again. they say that the dipole antenna creates half a wave, not a full wavelength. It has only the peaks of the waves at each end, but it creates a whole wavelength, when it goes back and forth. The charge in the antenna is bouncing back and forth from right to left and each time it hits the end and bounces back, the wave conforms to the same wave pattern, bouncing energy in each direction equally, but the flow of the EMR is going in mainly only one direction... the radiation is not equal, as you see, it goes more to the right than left, because of the reflectors but also because of how it projects the signal into the air. The signal leaves the antenna as the charge in the dipole hits the end, or reflector, and because of the way the two wave vectors keep things spinning one way, the dipole continues to project the signal in that direction, just weaker as the electrons in it are going backward, in it. That's my first guess. The dipole only needs to create half a wavelength to transmit a full wavelength. But i don't know what a full wavelength making thingy dealy would look like.
Brilliant I did an RAF course on ground wireless as a boy entrant in the 50's of course we had no video at the time. Photon energy transmission is the same mechanism and this illustrates that principle. The wonders of resonance from the breaking wine glass to a CO2 molecule?
The electrons do not flow, the energy wave does. Like water in the sea there's a difference between a sea wave and a sea current. For instance, an anchored boat keeps waving up and down but it is displaced by the current if the anchor is taken. In electricity this is known as displacement current (the actual electron movement from atom to atom which can lead to a different compound [electrolysis]) and conduction (wave) current.
A reflective surface is one with (ideally == totally reflecting) no resistance, so at the surface the solution to the wave equation, which is the sum of a forward traveling and reverse traveling wave cannot have an electric field (no electric field in a conductor). So to satisfy this boundary condition, the reverse traveling wave must have the opposite electric field so the sum at the surface is always 0. Hence, the exact impinging wave is reflected, inverted in polarity and summing with it. For a sine wave, this implies standing waves starting 1/4 wavelength from the surface and then at 1/2 wavelength intervals with nodes (no electric field ever) at the surface and then again at 1/2 wavelength intervals. Makes sense, eh? The magnetic field must stay the same for the Poynting vector to reverse, which identifies it as reflected, traveling the opposite directing. Just use the right hand rule for E x H for the impinging and reflected to verify this.
@@jonahansen This explanation should start on a simpler basis. The reflector an electrical conductor. It is not a magnetic 'conductor' (what would constitute a "magnetic conductor" might be interesting, but needn't detain us here). *The E-field is reversed in polarity by simple counter-EMF, just as it is with any electrical conductor.*
@K8BYP _ you are genius better than Einstein. Your circuit issue is your problem, not anyone else 's fault. Antenna is an integral part of the RF and it does not affect its performance ? Read more on 1/2,1, 1/4 ... wavelength dipole antenna to educate yourself.
It is sad just how much the education techniques and materials have degraded over the decades. (I think the Roman numeral year, at the end, is 1959) Now, price goes up, content goes down, quality disappears. This video reminds me of why college is such a waste of money today. I even fell for the college lie. It all worked out at the end by getting an unrelated job to what I studied. I am making far more than I could ever have made in the computer field, which is the unfortunate field I studied. None of the content was as methodically explained as this antenna theory. At least I paid my tuition loan in full, using my current job.
@@breakingthemasks I am a glorified grease monkey. I serve, repair, reprogram, hydraulic equipment, lorries, freezers, assembly lines, even the sales fleet vehicles of Estes Logistics. All I do is work with machinery all day. Granted, some of the work is network and computer related. But that is in all fields today. Should I have been a programmer at Blizzard Entertainment, I would max out around 180,000 for the very highest possible pay, which I likely would not have obtained. Today, I make far more than their senior programmers, their IT experts, their hardware engineers, and the such.
So the length is related to the frequency range you want to transmit and also the direction of propagation in your antana. You can build a quarter wave dipole that will propagate downward into a ground plane that pushes or reflects them. So you can build a directional antenna. I don't know how this works for a 3/4 wave antenna but. I'm trying to learn.
In this diagram animation BOTH the VOLTAGE and CURRENT (fields) are drawn as strongest in the middle of the antenna. As far as I know one of them should be stronger at the tips of the antenna and the other weak at the tips but strong at the feed points.
I think it depends on the wavelength relation of the antenna and where the feed point is. I recently saw a video that illustrated your exact point, but I'm trying to remember what was said. I found it by accident. I feel like it had to do with an end fed antenna, made at a fractional wavelength and showing why a center fed dipole is so desirable, but an end fed (while more practical in building and mounting) is a compromise electromagnetically. I think it was regarding building a 160m antenna. The guy was explaining the trade offs and difficulties in building such a long antenna for that band.
Not so - at 3:34 we see the current at one particular instant with a maximum in the center, and with minima (=zero in a perfect antenna) at the ends. Just a few seconds later, at 3:40, we see the voltage curve at that same instant with a minimum at the center, and maxima at each end. This is precisely what one would expect of a 1/4 wavelength conductor cut off at both ends - it is impossible for current to flow at the ends, so the current is low (=0) there, and the voltage must therefore be high there. To underline this, the commentator says "This current standing wave is 90 degrees out of phase with the voltage standing wave." Try watching it again.
1:04 - it should be noted that this visual representation is not a sign wave form but momentary pulses as it does not fade in and out. Indeed, radiating from one point wouldn't have the dynamic of traveling along a radiating element, so that doesn't mean it is necessarily incorrect, just not representative.
1:43 While electrons do move it is not the electrons themselves that are moving this distance but rather their electrical field, similar you could say to how a wave travels across water though the actual specific molecules of water aren't traveling the full length of the wave's propagation.
Wow, this is both confusing and boring at the same time. As a Ham radio operator, I'm glad I gained my practical understanding of antenna design and propagation from the ARRL Handbook & Antenna Book which both seemed to make perfect sense.
I thought they had the direction of the magnetic field wrong but electrons go reverse to current. It really should be with it, but I guess the left hand rule isn't as catchy.
Interesting that half way through they reversed the selection of colors (pink and blue) for the E field and the H field. I wonder if this was a mistake or on purpose?
Why is the magnetic field coming out from the antenna not even at any point? As far as I know electricity flows evenly in the wire,so why would the center have stronger field than the edges?
He says the peak happen in phase but the description at 5:00 implies they’re not…it’s as if the E and H aren’t maximized at same time in that illustration- which is wrong
on dipole electric and magnetic standing waves has 90 degrees phase difference. but propagating electric and magnetic waves has no phase difference. why and how?
as i understand shortly. propagating h (magnetic) wave produced by dipole electric wave, so they are in phase. since changing e fields produce magnetic field at the same phase. from this video maybe we can say whenever e and h waves at 90 phase difference, they produce propagating em waves at the same phase.
@@Discerner13 That is correct and that is what is misleading about the video. The immediate field or (Near field) is NOT the one that radiates. It is the Far Field and that is produced by ACCELERATING charges (not mentioned). Fields that are 90 degrees out of phase do not transfer power to space. They MUST be in-phase. The radiation phenomenon is left out. The rest of the video is correct.
The so-called flow of so-called electrons in an antenna or in any wire is a secondary effect. There is a slab of transverse E by H energy current flowing along the outside of the antenna/wire. As explained by Heaviside, Ivor Catt & Forrest Bishop. There is no such thing as charge or voltage. Also, skoolkids should be told that radio waves (ie so-called em waves) are a different animal to photons. And any explanation should involve aether.
@@robbannstrom I have recently realized that electricity on a wire is due to photons hugging the surface. A slightly different version of the Heaviside energy current.
Do I need to be licensed to translate to Spanish? I noticed that there is no text in the video, which made me think it would be an excellent pedagogical tool.
![Blox Fruits Dragon Rework Update [Full Stream]](http://i.ytimg.com/vi/EqDAp8udhm0/mqdefault.jpg)
Why can't all modern day RUclips educational videos start with an epically uplifting orchestra?
Right!? I was suddenly really excited to learn! It helps that the video then delivers actual no BS Lear ing content, but the orchestra definitely got me ready to learn.
@@pfmcdermott1, Nowadays our instructional videos sound like oontz oontz oontz with no explanations.
Thank you Royal Canadian Air Force for creating such an informative and aesthetically pleasing video. Coming from a US Marine decades later, this presentation helped me understand the fundamentals of wave propagation.
I didn't realize it was so simple to produce a radio wave. That explains why I see FFC sticker on almost everything. Electronic.
Back when Canada was great. Greetings all Canadian avionics folks here. Bob, if you're still around, thanks for the start in the career.
The Canadian people are still great!!! USA
Even today, October 2024, this is a very educational and well presented video. No fancy graphics or animation. Every EE student should view this video!
For weeks I've been looking for a video describing WHY half wavelength is SOOOO important in every conductor carrying a varying current. All videos I could find described the standing wave you create at the half wavelength, but failed to describe WHY it radiates that specific frequency. This video does the simple and yet very effective way of doing just that! Thank you to the uploader of this video!
Another feature of square bus bars would be to generate less rf?
I don't understand too? Can you explain
@@artie5172 To make the most efficient and simplest use of an antenna of any length, you want to push and pull the electrons along the full length of the antenna. To do this you’ll be switching the voltage from high (to pull them) to low (to push) whenever the electrons reach the close end of the antenna to the voltage source, and from low to high when they reach the far end.
If you waited for the electrons to do this you would have a wave length that is double the length of the antenna (while on the antenna you get the first magnetic peak in one direction but not the comeback peak with the reverse curl [negative sine wave] until the electrons are on their way back. You often want a shorter wavelength and can do this by switching from low to high voltage (push to pull) at 1/3 the length of the antenna and swithching back at 2/3rds so when the electrons reach the end you’re in the same position to switch from push to pull. You can actually add any arbitrary number of full wavelengths after you add the one half wavelength switch. So you could switch at 1/5 of 1/7 and add 2 or 3 full wavelengths after respectively. You’re still in the efficient position of going from push to pull when they finally reach the end of the antenna.
the simple dipole (basic antenna) radiates at lambda/2 frequency since it's in half period of a sinusoid that you can see at least 1 "back and forth flow" of the electrons, therefore in half the period (half the wavelength) you can send a high quality signal
This explains why a half wave antenna is used instead of a full wave. Finally I have a basic simplified understanding.
Now I totally get this topic. Videos like this are brilliant.
The narration level is good for 12 intelligent year old boy. What a success to inform public masses
This is absolutely fantastic as a visualization!
There's a far better, and even _older_ visualization at:
"Radio Antenna Fundumentals Part 1 1947" , RUclips (Fundumentals*)
Don't worry about the preliminary part. 16;28 will make the whole business of E and H field propagation crystal-clear, because of the particular visual viewpoint it gives.
After seeing that, then I come back to the present video at 5:13 and can now see the point of view they are presenting.
________
*the youtuber's spelling, not the Air Force's
I can't stress enough how this video helped this all finally make sense, just awesome.
❤😎 Love & Respect to the whole team for making this effort long-long back! It still helps
Man, the very best explanation, in years. Now I understand. Thank you!!!!
This video is really great! I like the way that they leave space and gives the viewer time so that the Info sinks in.
Perfectly straightforward and clear instructional video. Everything simply broken down to the basics and explained.
If it’s clear then why they do show current and voltage both weak at the tips of the antenna? One of these is strong at the tips, don’t you think?
Wow, the polar diagram explanation starting at around 9:00 minutes blew my mind. Very clear explanation. Thank you.
Good explanation connecting the standing waves of current and voltage to the strength of the magnetic and electric fields that are produced by them, respectively. And an excellent description of how the radiation pattern is sketched by first measuring the field strengths at points away from the antenna.
This video turned my life around.
I spent a couple of weeks with headaches reading various textbooks about this until it all sunk in. This makes it perfectly clear in 12 minutes and 25 seconds, (with the exception of the voltage/current phase relationship of the radiated signal.) The only thing I should point out is something that I originally confused myself about from seeing all those sine waves. The field doesn't actually have the 'shape' of a sine wave. The sine only represents the intensity of the energy and its field polarity reversal. It actually physically 'looks' more like like fluctuating soundwave pressures, (if you can imagine them with 2 phases and a polarity reversal.) Recall that electromagnetic waves have wave/particle duality, so they can also be pictured as a stream of photons of fluctuating density. Good luck with that bit, but you get my point. :)
I think you're wrong about this. Heinrich Hertz showed in the 1880s that radio waves are indeed 2 dimensional waves (transverse waves). Yes this may seem weird when you are forming a mental picture, but it is demonstrably true, and antennas depend upon this 2D physicality. Sound waves are longitudinal waves. They are indeed 3 dimensional.
Yeah I was ALWAYS confused with the sines regarding audio and em waves... The audio I understood by watching shockwaves. So I wanted to imagine EM waves the same. But I don't get this 90 degree between waves. I dont really understand these waves. I feel like I understand magnetic and electric field, but not a wave of them.
"Recall that electromagnetic waves have wave/particle duality"
That's an inherent contradiction.
In the mid-70's I used this as a training film (it was old, scratched 16mm celluloid film) when I was a USAF military adviser to the Imperial Iranian Air Force. Yes, Iran was an American ally at the time and the Shah was still on the Peacock Throne. So glad to find it online. For those who think this is crude compared to what you can create with today's technology, it was animated by hand, one frame at a time, just like Walt created Mickey in 1928.
thank you, interesting information
I have no idea how anyone could think this video is crude, it so eloquently describes such a complex operation.
Even grade 10 students will be able to understand from this video. Hat off 🙏🏻🙏🏻
I just learned more in 12 minutes than I have in the last 50 years.
Bravo Canada...........
So did I.
If you know about current and electromagnetism already, this is incredibly beautiful. Well made explanation what's going on!
Deusdat - I just received an email where you explained the incongruence regarding the phase of the electric and magnetic field, but it doesn't appear here. But it really does explain it - great thinking, thank you so much. I should have tried to think it through myself - but it needs to be here, so I'm going to copy and paste it from my email:
Deusdat replied:
My explanation: In fact, the accumulation of electrons at one end of the dipole is caused by the external voltage applied by an electronic amplifier. So it's this electric field that causes the crowding of the electrons, not the opposite. The current produced by these electrons is maximum at the beginning of their flow - and so is the magnetic field! Gradually the accumulation of electrons polarizes the dipole creating a secondary electric field that opposes the initial one. So there is a point when the total electric field is cancelled and the electron accumulation reaches its peak. The current is now zero - and the magnetic field is also zero. Conclusion: both fields are actually in phase, contrary to what is depicted in the video! The phase difference appears between the magnetic field and the polarization of the dipole (the secondary field), not the total electric field.
Very well done, dude or dudette, as the case my be!
Thanks, I wish I understood other things too. Antennas are a tricky matter.
That's a good explanation.
for such a short film, this is suprisingly informtive and easy to understand.
At 4:42 it is said that E-field and H-field are 90 degrees out of phase. Then they end up being in phase. I don't get it. Someone please explain that.
This is the only one from whole RUclips could explain this perfectly 🎉
this is phenomenal. thank you for posting.. Really explained simple to understand, thanks for efforts.
Very good. Thanks, now I learnt a lot more about antenna theory, but I need to keep learning and put the knowledge into action.
When people where forced to plan and draw animations by hand, they really needed to be creative and had the time to conceive such intuitive representations of highly abstract concepts. There are few modern hack-together-the-easiest-animation-your-software-enables-you-to videos that are as informative as this one.
I want a refund from my university. My instructor has his PhD in this and still couldn't explain it...
Sadly the tale of many universities today
@@owen7185 facts... guy who taught me signals and systems is a fraud lmao
@@bran_rx I believe you 💯💯
🤣🤣
😆
Brilliant explanation of the basics - thank you.
Great work, simple explanation, had to watch it twice to grasp
4:42-4:52 Shows the E field and the H field is 90 degrees out of phase but at 5:54-6:00 when we combine the component of E and H fields together, why both fields are in phase?
gothcha
*E : 1 0 1 0 1 0*
*H : 0 1 0 1 0 1*
yet this Video was great thou
Was thinking the exact same thing
I didn't think after that music it could get any better, but it did.
This is so intuitive I’m CONVINCED my EE degree was a total scam.
I tried to understand this many times.... Now I do!
Please post more videos. Much better explanation with the visualization than traditional textbook
Excellent. I knew nothing about how antennae’s worked and I have a good grasp. I loved the repetition at the end.
Great 👌
Fantastic explanation
Thanks to the lecturer
Big flaw: when describing the dipole behavior, H and E are in time quadrature (H is max when E is zero). Later on, when describing the electromagnetic wave, suddenly E and H are in phase.
This should have been explained...
Very well said! This is the part that always confuses me, and prevents me from understanding antennas. I've yet to find a good explanation on RUclips. I get that the fields at the antenna are "near field", and the propagating part is "far field", the latter propagating energy independent of the device that launched it. But how does it go from space quadrature to space in-phase?
Good observation. The exposition in this video is clearly simplified. In the dipole behaviour, what is shown is only the reactive part of the field, which dominates in the vicinity of the antenna, being the dipole a resonant (reactive) structure. The energy of this field is stored near the antenna and does not propagate. Thus, E and H field are in quadrature. But there is also another contribution, the radiation field, which is smaller but propagates far from the antenna, in which the E and H fields are in phase.
If you're familiar with AC circuits, that's exactly the same with voltage and current on a load.
I had to add a separate comment since RUclips is messing up. See it above/below. Thanks - it is excellent...
I observed the same stuff
watch it again. they say that the dipole antenna creates half a wave, not a full wavelength. It has only the peaks of the waves at each end, but it creates a whole wavelength, when it goes back and forth. The charge in the antenna is bouncing back and forth from right to left and each time it hits the end and bounces back, the wave conforms to the same wave pattern, bouncing energy in each direction equally, but the flow of the EMR is going in mainly only one direction... the radiation is not equal, as you see, it goes more to the right than left, because of the reflectors but also because of how it projects the signal into the air. The signal leaves the antenna as the charge in the dipole hits the end, or reflector, and because of the way the two wave vectors keep things spinning one way, the dipole continues to project the signal in that direction, just weaker as the electrons in it are going backward, in it. That's my first guess. The dipole only needs to create half a wavelength to transmit a full wavelength. But i don't know what a full wavelength making thingy dealy would look like.
Really explained simple to understand, thanks for efforts
Can this be made for VR? I only understand VR
Wait....at 2:47 are those field lines supposed to be going the other direction by the way the current is travelling and the right hand rule?
The right hand rule uses the conventional current flow, that is opposite the real flow of electrons. In the video, is showed the flow of electrons...
Brilliant I did an RAF course on ground wireless as a boy entrant in the 50's of course we had no video at the time. Photon energy transmission is the same mechanism and this illustrates that principle. The wonders of resonance from the breaking wine glass to a CO2 molecule?
The electrons do not flow, the energy wave does. Like water in the sea there's a difference between a sea wave and a sea current. For instance, an anchored boat keeps waving up and down but it is displaced by the current if the anchor is taken. In electricity this is known as displacement current (the actual electron movement from atom to atom which can lead to a different compound [electrolysis]) and conduction (wave) current.
If I can interject here: Electrons do, in fact, flow
soo dont electrons flow? Batteries work by moving charge from one terminal to another one.
@@PinkeySuavo Charge yes but not Electrons, they barely move and aren't even particles in the first place.
why did the E vector switched directions when hitting a reflective surface but H didn't?
A reflective surface is one with (ideally == totally reflecting) no resistance, so at the surface the solution to the wave equation, which is the sum of a forward traveling and reverse traveling wave cannot have an electric field (no electric field in a conductor). So to satisfy this boundary condition, the reverse traveling wave must have the opposite electric field so the sum at the surface is always 0. Hence, the exact impinging wave is reflected, inverted in polarity and summing with it. For a sine wave, this implies standing waves starting 1/4 wavelength from the surface and then at 1/2 wavelength intervals with nodes (no electric field ever) at the surface and then again at 1/2 wavelength intervals. Makes sense, eh? The magnetic field must stay the same for the Poynting vector to reverse, which identifies it as reflected, traveling the opposite directing. Just use the right hand rule for E x H for the impinging and reflected to verify this.
@@jonahansen My brain just exploded.
@@knife-wieldingspidergod5059 yeah me too
@@jonahansen
This explanation should start on a simpler basis. The reflector an electrical conductor.
It is not a magnetic 'conductor' (what would constitute a "magnetic conductor" might be interesting, but needn't detain us here).
*The E-field is reversed in polarity by simple counter-EMF, just as it is with any electrical conductor.*
How E and H fields which are out of phase near the antenna , attain same phase after a certain distance ?
My question exactly. No explanation anywhere that I've been able to find and I've looked.
I think any length of the dipole from one end to the other still radiate but full/2 (half) wavelength give you the most and consistent radiation.
You're right. Any integer multiple of half wavelength will make the dipole resonate and therefore radiate at its maximum capability.
@K8BYP _ you are genius better than Einstein. Your circuit issue is your problem, not anyone else 's fault. Antenna is an integral part of the RF and it does not affect its performance ? Read more on 1/2,1, 1/4 ... wavelength dipole antenna to educate yourself.
@K8BYP _ David, you come across sounding like a jerk here.
It is sad just how much the education techniques and materials have degraded over the decades. (I think the Roman numeral year, at the end, is 1959) Now, price goes up, content goes down, quality disappears. This video reminds me of why college is such a waste of money today. I even fell for the college lie. It all worked out at the end by getting an unrelated job to what I studied. I am making far more than I could ever have made in the computer field, which is the unfortunate field I studied. None of the content was as methodically explained as this antenna theory. At least I paid my tuition loan in full, using my current job.
What kind of job did you get?
I think education material should be updated, especially in engineering fields. They are teaching too much irrelevant information.
@@breakingthemasks I am a glorified grease monkey. I serve, repair, reprogram, hydraulic equipment, lorries, freezers, assembly lines, even the sales fleet vehicles of Estes Logistics. All I do is work with machinery all day. Granted, some of the work is network and computer related. But that is in all fields today. Should I have been a programmer at Blizzard Entertainment, I would max out around 180,000 for the very highest possible pay, which I likely would not have obtained. Today, I make far more than their senior programmers, their IT experts, their hardware engineers, and the such.
So the length is related to the frequency range you want to transmit and also the direction of propagation in your antana. You can build a quarter wave dipole that will propagate downward into a ground plane that pushes or reflects them. So you can build a directional antenna. I don't know how this works for a 3/4 wave antenna but. I'm trying to learn.
This was a great introduction. Thanks for sharing!
I’ve only know the sine wave form but never seen anything like this ..More visual dimension trough this video wow
I was definitely thinking an episode of Tom and Jerry was about to start after that intro..
Damn as a Canadian signals soldier I never knew we used to make cool videos like this
2:30 can we actually imagine it as squeezing electrons? Aren't they in similar distances all the time?
Screw it, I’m never calling the right hand rule again. Pun absolutely intended
Best electromagnetics course ever.
Wow,realy very excellent tuition
In this diagram animation BOTH the VOLTAGE and CURRENT (fields) are drawn as strongest in the middle of the antenna. As far as I know one of them should be stronger at the tips of the antenna and the other weak at the tips but strong at the feed points.
I think it depends on the wavelength relation of the antenna and where the feed point is. I recently saw a video that illustrated your exact point, but I'm trying to remember what was said. I found it by accident. I feel like it had to do with an end fed antenna, made at a fractional wavelength and showing why a center fed dipole is so desirable, but an end fed (while more practical in building and mounting) is a compromise electromagnetically. I think it was regarding building a 160m antenna. The guy was explaining the trade offs and difficulties in building such a long antenna for that band.
Not so - at 3:34 we see the current at one particular instant with a maximum in the center, and with minima (=zero in a perfect antenna) at the ends. Just a few seconds later, at 3:40, we see the voltage curve at that same instant with a minimum at the center, and maxima at each end. This is precisely what one would expect of a 1/4 wavelength conductor cut off at both ends - it is impossible for current to flow at the ends, so the current is low (=0) there, and the voltage must therefore be high there. To underline this, the commentator says "This current standing wave is 90 degrees out of phase with the voltage standing wave." Try watching it again.
Thank you so much for the video. It really helped me a Lot in understanding fundamentals
Great explanation.
This is simply awesome! I recommend that students see this video before reading any of those intimidating books! lol
Superb !!
Brilliant explanation.
Amazing animation!
what's the difference betwwen near field and far field EM-physics?
1:04 - it should be noted that this visual representation is not a sign wave form but momentary pulses as it does not fade in and out. Indeed, radiating from one point wouldn't have the dynamic of traveling along a radiating element, so that doesn't mean it is necessarily incorrect, just not representative.
1:43 While electrons do move it is not the electrons themselves that are moving this distance but rather their electrical field, similar you could say to how a wave travels across water though the actual specific molecules of water aren't traveling the full length of the wave's propagation.
Wow, this is both confusing and boring at the same time. As a Ham radio operator, I'm glad I gained my practical understanding of antenna design and propagation from the ARRL Handbook & Antenna Book which both seemed to make perfect sense.
"the traveling wave is in time phase and space qudrature" What does time phase mean in this context?
Right so, what's a wave again?
I thought they had the direction of the magnetic field wrong but electrons go reverse to current. It really should be with it, but I guess the left hand rule isn't as catchy.
Man, old dudes must use 100% mind power and 100% effort, creating such billiant people.
great explanation
Simply the best.
Interesting that half way through they reversed the selection of colors (pink and blue) for the E field and the H field. I wonder if this was a mistake or on purpose?
very nice this record looks very old but animations are great
Does the digital broadcast change this principle at all? (e.g. HD radio, HD tv signal, etc.)
No. Simply put, The signal is encoded and added to the EM wave and then decoded at the far end.
Doug LeBlanc
Understand that the signal may be analog or digital, but the frequency (EM wave) carrying the signal stays the same.
Thanks.
Why is the magnetic field coming out from the antenna not even at any point? As far as I know electricity flows evenly in the wire,so why would the center have stronger field than the edges?
If you build an antenna half the length of a light wave and power it in the classical way by arc, will it send and receive light waves?
what do you mean “arc”?
@@antonwang120 Like at welding, or like the first dipole antenna was powered. For 1 micrometer, you need less than 1 Volt to create a sparkover.
Appreciate your time in making the video. Thanks deeply from my heart!
What a perfect explanation!!
He says the peak happen in phase but the description at 5:00 implies they’re not…it’s as if the E and H aren’t maximized at same time in that illustration- which is wrong
Where to find more videos like this ? Completely amazing , plz tell anyone
Look for army training videos. There are some good ones frlm is army and navy
@@breakingthemasks thanks
@@vaibhavbhasin3861 ... ruclips.net/video/s1i-dnAH9Y4/видео.html
Etc 👍
Still dont get why first the the E and H field are 90 degrees out of phase but suddenly they are in phase 😢
Yah i am thinking this also that they should be 90 our of phase
Very valuable information!
this is phenomenal. thank you for posting.
on dipole electric and magnetic standing waves has 90 degrees phase difference. but propagating electric and magnetic waves has no phase difference. why and how?
as i understand shortly. propagating h (magnetic) wave produced by dipole electric wave, so they are in phase. since changing e fields produce magnetic field at the same phase.
from this video maybe we can say whenever e and h waves at 90 phase difference, they produce propagating em waves at the same phase.
Great video!
Great stuff , my cup of tea
great video
Great Video.. but is there a phase difference between E and H fields?
Yes. The E-field leads by 90 degrees
In the antenna yes, but in the far field they are in phase.
@@Discerner13 That is correct and that is what is misleading about the video. The immediate field or (Near field) is NOT the one that radiates. It is the Far Field and that is produced by ACCELERATING charges (not mentioned). Fields that are 90 degrees out of phase do not transfer power to space. They MUST be in-phase. The radiation phenomenon is left out. The rest of the video is correct.
@@powertube5671 cool! Where can I find more about what you are saying?
now all it needs is more title screens and dramatic music
Best to start, need more vedios on transient radiation from antenna if possible
Great video
Thank you very much for this video...
That illustration is misleading at 5:00, the E field and H field are in phase, there’s no capacitance here right it is an ideal conductor
The so-called flow of so-called electrons in an antenna or in any wire is a secondary effect.
There is a slab of transverse E by H energy current flowing along the outside of the antenna/wire.
As explained by Heaviside, Ivor Catt & Forrest Bishop.
There is no such thing as charge or voltage.
Also, skoolkids should be told that radio waves (ie so-called em waves) are a different animal to photons.
And any explanation should involve aether.
Typical comment from a person who understands nothing of science.
@@robbannstrom
I have recently realized that electricity on a wire is due to photons hugging the surface.
A slightly different version of the Heaviside energy current.
@@atheistaetherist2747 You very evidently do not live in the same world as standard science. Good luck with that.
@@robbannstrom
True. I do not believe in the big bang, gravity waves, etc.
We are in the Einsteinian Dark Age of science.
Do I need to be licensed to translate to Spanish? I noticed that there is no text in the video, which made me think it would be an excellent pedagogical tool.
Please reach out to library-archives.canada.ca/eng/collection/basics/Pages/who-we-are.aspx
@@Bonkers01 Thank you for the advice!
@ 0:47 A STATIONARY POINT-SOURCE DOES NOT EMIT EM-RADIATON.
Beautiful!
Isn't it!
no wonder instagram isnt working on my phone