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.
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
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.
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.
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!
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.
@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.
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.
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.*
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.
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.
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.
This movie is based on old theory of the production of electromagnetic energy. Maxwell's equations predicted the formation of the direction of travel of the energy when an electric field and a magnetic field at right angles produces a force carrier at 90 degrees to the other 2 fields. Called the Poynting vector. In modern physic, Richard Feynman won a Nobel prize for his discovery of the electromagnetic force carrier. Feynman discovered that a photon consists of an electron and a positron pair which interact with each other. Over a cycle or period of photon energy exchange (the period is the inverse of the frequency), the electron will interact with a positron to form, for a brief instance, pure energy. The matter of the 2 particles becomes an energy function. The energy function cannot exist in its pure form for long, and condenses back to matter. The time this particle interaction takes place is the period of the photon, and determines the speed of movement. The energy function always forms at right angles to the spin or momentum of the 2 particles and thus moves in a direction perpendicular to the particle momentum. The electron moves in one direction (E) and the motion generates a magnetic particle (a momentum component change of the electron sometimes called a magnetron?) (H) perpendicular to it. The E direction will determine the location of the electron and is described as the polarity function. In physics, the photon is called the force carrier of the electromagnetic force. Radio waves are just long wavelength photons. Photons are produced when electrons jump energy levels around an atom. For short distances, such as the those around an atomic nucleus, the wavelength is very short and we see the photons as visible light. However electrons can also interact with other electrons and the resulting interaction can produce a whole series of different wavelength photons depending on the energy the electrons had at the time of interaction. This is all basic particle physics you will find in a good university text book. Now radio waves, as I said, are long wavelength photons and are created by the particle interactions inside the wire which must contain a significant number of free or loosely bound electrons. The antenna is connected to a source of electrons driven by a high potential energy force which is coming from the transmitter and its supply. The energy imparted to electrons in the wire causes bunching, and at certain points in the conductor, there is a potential peak and and at other points a potential well (you need to understand quantum physics to get a better idea here). During the particle collisions, positrons form, and once that happens, a free electron will be attracted to the positive charge, and now a photon forms. And that photon must move at right angles to the particles in the wire and hence move away into space. Once that happens we have what we call radio waves. Once away from the wire, the 2 particles continue to move and now interact with something we know little about - we give it a value of 377 ohms but in reality, scientists believe it may be the Higgs field which gives matter its form (now you need to read into much deeper physics here about symmetry theory -- fermions, Bosons, Quarks, etc.). The subject of what really happens is quite deep and scientist still do not have a good idea what an electron and a positron are - electrons seem to behave both as waves and particles. So if you want to know more, read some good books on particle physics and quantum theory. But one thing is certain - there is a lot more to the physics of what actually happens in a radio antenna - and there is no such thing as waves - waves only exist when a medium transports energy across its width or field. Radio waves are actually particles - long wavelength photons - not waves or fields - yes they move through a field (Higgs field?) but they are not the field or even a wave.
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?
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
@@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.
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.
This a very poor explanation as there is so much missing,. But I don't know what level or understanding is a prerequisite. I was taught RF principles antenna design with a lot more reference to first principles.
For an electron to radiate Electromagnetic (EM) radiation, it needs to accelerate. To accelerate, the electron must change speed or direction. This radiation phenomenon only exists in AC - with DC the electrons move in one direction. All of the EM spectrum (radio, visual light, x-rays, etc - choose any frequency) radiate as both electric and magnetic waves. Hope this answers your question.
@@jonahansen - Wait, I thought the Michelson & Morley experiment was unable to detect any aether, since the Earth's movement through space produced no measurable effects on their interferometer? Or, was it that their instrument was compressed in the direction of travel, and thus was unable to measure the effect of motion through space?
Sergio Specalsiki Good question. According to NASA, electromagnetic/radio waves was proven to be a form of light. This brings up the next dilemma of whether light is a particle or a wave. Asking the question, “How does the sun radiate energy to Earth,” is essentially asking the same as your question. I think the concept of “the ether” was disproven long time ago. So, it could only be the Force. science.nasa.gov/ems/02_anatomy
@@solarfluxman8810 Sorry dude. I was being facetious by saying the ether was found to be free space itself, meaning no medium was necessary, and that is why they didn't detect any difference. I think you are bringing relativity into it unnecessarily, as only a different observer not moving with the earth would measure a change in lengths, and relativity hadn't yet been "discovered" anyway at that time. All the measurements were in a single frame of reference and no length changes were measured or even hypothesized. I'm getting beyond my real depth of knowledge here, though. I'll shut up.
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.
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
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.
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.
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?
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.
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?
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.
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.
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.
❤😎 Love & Respect to the whole team for making this effort long-long back! It still helps
The narration level is good for 12 intelligent year old boy. What a success to inform public masses
Wow, the polar diagram explanation starting at around 9:00 minutes blew my mind. Very clear explanation. Thank you.
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.
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.
If you know about current and electromagnetism already, this is incredibly beautiful. Well made explanation what's going on!
This video turned my life around.
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.
Screw it, I’m never calling the right hand rule again. Pun absolutely intended
This is the only one from whole RUclips could explain this perfectly 🎉
for such a short film, this is suprisingly informtive and easy to understand.
I tried to understand this many times.... Now I do!
This is so intuitive I’m CONVINCED my EE degree was a total scam.
Very good. Thanks, now I learnt a lot more about antenna theory, but I need to keep learning and put the knowledge into action.
this is phenomenal. thank you for posting.. Really explained simple to understand, thanks for efforts.
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.
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.
I’ve only know the sine wave form but never seen anything like this ..More visual dimension trough this video wow
Man, old dudes must use 100% mind power and 100% effort, creating such billiant people.
I was definitely thinking an episode of Tom and Jerry was about to start after that intro..
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.
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.*
This is simply awesome! I recommend that students see this video before reading any of those intimidating books! lol
Damn as a Canadian signals soldier I never knew we used to make cool videos like this
love the needlessly dramatic music on the credits
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.
This was a great introduction. Thanks for sharing!
Great explanation.
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.
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.
Can this be made for VR? I only understand VR
Amazing animation!
"the traveling wave is in time phase and space qudrature" What does time phase mean in this context?
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.
Thank you so much for the video. It really helped me a Lot in understanding fundamentals
Wow,realy very excellent tuition
this makes me want to take an engineering course
First learn how to use capitals and proper punctuation...
@@eknaap8800 he is not writing an exam here he just wrote a comment.stop banging your english tutor.
Brilliant explanation.
2:30 can we actually imagine it as squeezing electrons? Aren't they in similar distances all the time?
This movie is based on old theory of the production of electromagnetic energy. Maxwell's equations predicted the formation of the direction of travel of the energy when an electric field and a magnetic field at right angles produces a force carrier at 90 degrees to the other 2 fields. Called the Poynting vector. In modern physic, Richard Feynman won a Nobel prize for his discovery of the electromagnetic force carrier. Feynman discovered that a photon consists of an electron and a positron pair which interact with each other. Over a cycle or period of photon energy exchange (the period is the inverse of the frequency), the electron will interact with a positron to form, for a brief instance, pure energy. The matter of the 2 particles becomes an energy function. The energy function cannot exist in its pure form for long, and condenses back to matter. The time this particle interaction takes place is the period of the photon, and determines the speed of movement. The energy function always forms at right angles to the spin or momentum of the 2 particles and thus moves in a direction perpendicular to the particle momentum. The electron moves in one direction (E) and the motion generates a magnetic particle (a momentum component change of the electron sometimes called a magnetron?) (H) perpendicular to it. The E direction will determine the location of the electron and is described as the polarity function. In physics, the photon is called the force carrier of the electromagnetic force. Radio waves are just long wavelength photons. Photons are produced when electrons jump energy levels around an atom. For short distances, such as the those around an atomic nucleus, the wavelength is very short and we see the photons as visible light. However electrons can also interact with other electrons and the resulting interaction can produce a whole series of different wavelength photons depending on the energy the electrons had at the time of interaction. This is all basic particle physics you will find in a good university text book. Now radio waves, as I said, are long wavelength photons and are created by the particle interactions inside the wire which must contain a significant number of free or loosely bound electrons. The antenna is connected to a source of electrons driven by a high potential energy force which is coming from the transmitter and its supply. The energy imparted to electrons in the wire causes bunching, and at certain points in the conductor, there is a potential peak and and at other points a potential well (you need to understand quantum physics to get a better idea here). During the particle collisions, positrons form, and once that happens, a free electron will be attracted to the positive charge, and now a photon forms. And that photon must move at right angles to the particles in the wire and hence move away into space. Once that happens we have what we call radio waves. Once away from the wire, the 2 particles continue to move and now interact with something we know little about - we give it a value of 377 ohms but in reality, scientists believe it may be the Higgs field which gives matter its form (now you need to read into much deeper physics here about symmetry theory -- fermions, Bosons, Quarks, etc.). The subject of what really happens is quite deep and scientist still do not have a good idea what an electron and a positron are - electrons seem to behave both as waves and particles. So if you want to know more, read some good books on particle physics and quantum theory. But one thing is certain - there is a lot more to the physics of what actually happens in a radio antenna - and there is no such thing as waves - waves only exist when a medium transports energy across its width or field. Radio waves are actually particles - long wavelength photons - not waves or fields - yes they move through a field (Higgs field?) but they are not the field or even a wave.
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
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...
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?
this is phenomenal. thank you for posting.
Very valuable information!
Great stuff , my cup of tea
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
What a perfect explanation!!
Great video!
Best to start, need more vedios on transient radiation from antenna if possible
I like how they say negative energy and it you flip the probes them it will be opposite
Super
what's the difference betwwen near field and far field EM-physics?
nice, now I can place my wifi antenna perfectly, so that it can connect to my neighbor's wifi
Old videos make current generations dump.
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?
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 👍
Hi Doug, I was wondering if you knew the date this video was made? Im doing a presentation on animation in the 1950s and would like to use it.
Hi Erin. archive.org/details/antennafundamentalspropagation
Good luck!
Amazing
Thank you from Texas!
thank you
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!
Thanks
I'm a medico and I can understand this! 😃
nearly perfect !
For this next 1x 40 minute period ...
Thank you soooooooo much 🙏🙏🙏🙏🙏🙏🙏🙏🙏🙏🙏🙏🙏
Wow
Awesome
Waves and oscillation a good book butt a complicated read
Good sharing! 73 de VR2WAX, over!
👍
Best
Just a basket of 💎💎💎💎💎💎💎💎
This is incorrect. H-Field is Magnetic. Their vector labeling is backwards...
Rewatch the video mate
Welp....time to get serious...
Anyone else see wabbafett in that far feild plot?
I saw wabbet!
Lmao the intro was so grandiose
This a very poor explanation as there is so much missing,. But I don't know what level or understanding is a prerequisite. I was taught RF principles antenna design with a lot more reference to first principles.
bounsieng
I've absolutely no idea what you're trying to say. Use a dictionary!
🤭🍿 🤭🍿😋
Save nature by destroying the real source of ancient knowledge
Bullshit!
Never, Ever, anyone talks about..... What the hell is waving?
What is the medium?
For an electron to radiate Electromagnetic (EM) radiation, it needs to accelerate. To accelerate, the electron must change speed or direction. This radiation phenomenon only exists in AC - with DC the electrons move in one direction. All of the EM spectrum (radio, visual light, x-rays, etc - choose any frequency) radiate as both electric and magnetic waves. Hope this answers your question.
1) Electric and Magnetic fields 2) The ether, found to be free space itself by Michelson & Morley in a classic experiment in the late 1800s.
@@jonahansen - Wait, I thought the Michelson & Morley experiment was unable to detect any aether, since the Earth's movement through space produced no measurable effects on their interferometer? Or, was it that their instrument was compressed in the direction of travel, and thus was unable to measure the effect of motion through space?
Sergio Specalsiki
Good question.
According to NASA, electromagnetic/radio waves was proven to be a form of light. This brings up the next dilemma of whether light is a particle or a wave. Asking the question, “How does the sun radiate energy to Earth,” is essentially asking the same as your question.
I think the concept of “the ether” was disproven long time ago. So, it could only be the Force.
science.nasa.gov/ems/02_anatomy
@@solarfluxman8810 Sorry dude. I was being facetious by saying the ether was found to be free space itself, meaning no medium was necessary, and that is why they didn't detect any difference. I think you are bringing relativity into it unnecessarily, as only a different observer not moving with the earth would measure a change in lengths, and relativity hadn't yet been "discovered" anyway at that time. All the measurements were in a single frame of reference and no length changes were measured or even hypothesized. I'm getting beyond my real depth of knowledge here, though. I'll shut up.
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 💯💯
🤣🤣
You’re the one dumb enough to go to “college” for an “education” hahah.
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.
I can't stress enough how this video helped this all finally make sense, just awesome.
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
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.
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.
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
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.
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?
Back when Canada was great. Greetings all Canadian avionics folks here. Bob, if you're still around, thanks for the start in the career.
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?
no wonder instagram isnt working on my phone
another old jem