The way i understand it at 27:19 is that Professor Tougaw is taking the magnitude of E to be Etheta times the complex conjugate of Etheta and then taking the squre root: |E| = [(E)*(E*)]ˆ1/2. This is the definition of the magnitude of a vector and this vector E has only one component along the theta direction. When you take the complex conjugate you change i wherever it appears to -i (or j -> -j for electrical engineers).
3:42 correction: the voltages are the same magnitude, just opposite polarities, so it's not quite accurate to describe the dipole ends as "high or low".
A mistake, i think. The animation bet 8:25 to 8:50 is showing an emag signal incident on a dipole antenna which is a *receiver* antenna, given the load resistor R and absence of any driving voltage source. What he said "E and H are being generated by the current and propagating away" is for a transmitting dipole antenna.
Hi, overall fantastic content, however, I'm not sure how in Figure.2 the current is towards a higher potential - is it a matter of convention? The receiver animation has the electric field lines creating a potential in the opposite direction, why?
Nice video! At 47:36 into the video, you describe the components of a Yagi-Uda antenna. I'm quite surprised at how wrong you were in that description. Starting at the left of the illustration, the first 3 elements are all Directors, the next element is the Driven Element (or dipole as you refer to it) and the last element all the way to the right end of the illustration is the Reflector. This particular yagi uses a Folded Dipole for the driven element.
With reference to figure 30.3 on page 4 ... can the magnitude of the current (at the centre of the dipole), at the moment just before the signal radiates, be measured in metres? I can visualise the length of a (half wave) dipole in metres and would like be able to visualise the magnitude in the same way. I appreciate the magnitude will depend on many factors including frequency and power generated at the source. Thank you.
Neville, I don't think it is typical to represent the magnitude of the current in units of meters. It is typically measured in amps. However, all visualizations are only useful in that they help us to better understand and predict the behavior of the system. If you are able to measure the magnitude as a form of distance, and it helps you to better understand and predict the system's behavior, then it is useful for you to do so.
@@dougtougaw7681 Thank you so much for replying. I appreciate current is (typically) measured in amps but the figure 30.3 representation is so typical I've often wondered if there is a way to calculate (convert) the magnitude in metres. One of the reasons for my curiosity is how the wave interacts with a (dipole) coaxial feedline. One of the properties of coax is to prevent the inner conductor from radiating beyond its shield (please correct me if that's not the case). If that's the case I presume the magnitude must be millimetres or less to prevent distortion of the sinusoidal form??
@@nevmarrI think that the image in Figure 30.3 is really just a convenient and schematic way to represent the current in a way that helps to explain the situation to readers and students. I don't really know of a way to represent current as a distance as you suggest, but I do see what you mean about how it could be a useful conceptual tool. Thanks!
Suggestion sir. Pls prove that voltage distribution, current distribution, Electric and Magnetic fields distribution based on those diagrams will obey Maxwell equations for EM?
In the animated gif how the current is changing its direction in the first half of the sine wave at discharging? That will make the magnetic field 90 degree out of phase with electric field ..
the self-propagation of electromagnetic waves is a phenomenon of energy imbalance in a universe that seeks equilibrium. thus, this disturbance carries out to a spacetime of lesser energy.
So sorry to tell you, that a yagi has only one (1) dipole, and it doesn't get better if you attach multiple dipoles. A yagi antenna consist of one (1) Reflector, one (1) Dipole and a single or multiple Directors. The reflector are the longest, placed at the rear of the yagi, after that are the dipole, and then in front are the directors. I do have to look through some of your other videos to see if there should be some information on magnetic loop antennas. I find them very interesting.
At the antenna you show both the electric field and magnetic fields but not their relationships in time. At the antenna, the electric field and the magnetic field are perpendicular in space and 90 degrees out of phase in time. Do you agree? Thanks. See this by what I mean: en.wikipedia.org/wiki/Antenna_(radio)#/media/File:Dipole_antenna_standing_waves_animation_461x217x150ms.gif
@@dougtougaw7681 Thanks for your reply Doug. As an electrical engineer, if I measured the magnetic and electric fields at the antenna with my handy oscilloscope and probes, I would expect to see the same electric and magnetic fields be time delayed by 90 degrees too as in the gif. Do you concur?
Professor Tougaw, this is excellent. Loved your lecture. Couple points I'd like to raise from your video 1. It appears that neither end of the function generator is really connected to the ground plane. This means that the function generator can be seen as having a differential ended output with reference to the ground plane. Is this characterization correct? 2. Second, it appears that current is due to movement of both positive and negative charges. Isn't charge flow in conductors (of which these transmission lines are composed) primarily due to negative charges, i.e. electrons
Sanjay, Yes, I believe you could consider the function generator to be generating a differential signal, with neither side grounded. It's often simpler to discuss the motion of either only positive charges or negative charges, but this is only done as a simplification. In reality, only the negative charges move. As a colleague of mine says, if the positive charges are moving, you've got bigger problems!
@@dougtougaw7681 Thank you for your reply, Sir. This really clarifies a few things that were blocking further understanding. I'm reading your book and really enjoying it. I can't do more than contemplate one concept per sitting, but I'm finding that very stimulating.
The way i understand it at 27:19 is that Professor Tougaw is taking the magnitude of E to be Etheta times the complex conjugate of Etheta and then taking the squre root: |E| = [(E)*(E*)]ˆ1/2. This is the definition of the magnitude of a vector and this vector E has only one component along the theta direction. When you take the complex conjugate you change i wherever it appears to -i (or j -> -j for electrical engineers).
32:02 great animation, sir tougaw
47:49 another sweet animation of the Yagi-Uda transmission antenna
3:42 correction: the voltages are the same magnitude, just opposite polarities, so it's not quite accurate to describe the dipole ends as "high or low".
A mistake, i think. The animation bet 8:25 to 8:50 is showing an emag signal incident on a dipole antenna which is a *receiver* antenna, given the load resistor R and absence of any driving voltage source. What he said "E and H are being generated by the current and propagating away" is for a transmitting dipole antenna.
Hi, overall fantastic content, however, I'm not sure how in Figure.2 the current is towards a higher potential - is it a matter of convention?
The receiver animation has the electric field lines creating a potential in the opposite direction, why?
Nice video! At 47:36 into the video, you describe the components of a Yagi-Uda antenna. I'm quite surprised at how wrong you were in that description. Starting at the left of the illustration, the first 3 elements are all Directors, the next element is the Driven Element (or dipole as you refer to it) and the last element all the way to the right end of the illustration is the Reflector. This particular yagi uses a Folded Dipole for the driven element.
Thank you for clarifying this point. I'll correct it the next time I update this video.
They can calculate the cubic capacity of the pickle jar but cant take the lid off.. I cant follow the math much but ive built some big antennas...
@@dougtougaw7681 The figure you show after is correct and labled correct - mutlple directors, one dipole, and one long reflector.
With reference to figure 30.3 on page 4 ... can the magnitude of the current (at the centre of the dipole), at the moment just before the signal radiates, be measured in metres? I can visualise the length of a (half wave) dipole in metres and would like be able to visualise the magnitude in the same way. I appreciate the magnitude will depend on many factors including frequency and power generated at the source. Thank you.
Neville,
I don't think it is typical to represent the magnitude of the current in units of meters. It is typically measured in amps. However, all visualizations are only useful in that they help us to better understand and predict the behavior of the system. If you are able to measure the magnitude as a form of distance, and it helps you to better understand and predict the system's behavior, then it is useful for you to do so.
@@dougtougaw7681 Thank you so much for replying. I appreciate current is (typically) measured in amps but the figure 30.3 representation is so typical I've often wondered if there is a way to calculate (convert) the magnitude in metres. One of the reasons for my curiosity is how the wave interacts with a (dipole) coaxial feedline. One of the properties of coax is to prevent the inner conductor from radiating beyond its shield (please correct me if that's not the case). If that's the case I presume the magnitude must be millimetres or less to prevent distortion of the sinusoidal form??
@@nevmarrI think that the image in Figure 30.3 is really just a convenient and schematic way to represent the current in a way that helps to explain the situation to readers and students. I don't really know of a way to represent current as a distance as you suggest, but I do see what you mean about how it could be a useful conceptual tool. Thanks!
Suggestion sir. Pls prove that voltage distribution, current distribution, Electric and Magnetic fields distribution based on those diagrams will obey Maxwell equations for EM?
Thanks!!!
It was such a mystery how the Yagi or should I say Uda antenna worked.
In the animated gif how the current is changing its direction in the first half of the sine wave at discharging? That will make the magnetic field 90 degree out of phase with electric field ..
the self-propagation of electromagnetic waves is a phenomenon of energy imbalance in a universe that seeks equilibrium. thus, this disturbance carries out to a spacetime of lesser energy.
So sorry to tell you, that a yagi has only one (1) dipole, and it doesn't get better if you attach multiple dipoles.
A yagi antenna consist of one (1) Reflector, one (1) Dipole and a single or multiple Directors.
The reflector are the longest, placed at the rear of the yagi, after that are the dipole, and then in front are the directors.
I do have to look through some of your other videos to see if there should be some information on magnetic loop antennas. I find them very interesting.
Thank you. This is a community efforts, the doctor do a great work and our work is identifying and correcting errors to benefit our community
Is this from a book I can buy/download
At the antenna you show both the electric field and magnetic fields but not their relationships in time. At the antenna, the electric field and the magnetic field are perpendicular in space and 90 degrees out of phase in time. Do you agree? Thanks.
See this by what I mean:
en.wikipedia.org/wiki/Antenna_(radio)#/media/File:Dipole_antenna_standing_waves_animation_461x217x150ms.gif
Bela,
If I understand correctly, then yes, I do agree with you.
Doug Tougaw
@@dougtougaw7681 Thanks for your reply Doug. As an electrical engineer, if I measured the magnetic and electric fields at the antenna with my handy oscilloscope and probes, I would expect to see the same electric and magnetic fields be time delayed by 90 degrees too as in the gif. Do you concur?
@@belaji Yes, I believe that is correct.
the link to download the book please
Here you go: scholar.valpo.edu/engineering_oer/1/
Professor Tougaw, this is excellent. Loved your lecture.
Couple points I'd like to raise from your video
1. It appears that neither end of the function generator is really connected to the ground plane. This means that the function generator can be seen as having a differential ended output with reference to the ground plane. Is this characterization correct?
2. Second, it appears that current is due to movement of both positive and negative charges. Isn't charge flow in conductors (of which these transmission lines are composed) primarily due to negative charges, i.e. electrons
Sanjay,
Yes, I believe you could consider the function generator to be generating a differential signal, with neither side grounded.
It's often simpler to discuss the motion of either only positive charges or negative charges, but this is only done as a simplification. In reality, only the negative charges move. As a colleague of mine says, if the positive charges are moving, you've got bigger problems!
@@dougtougaw7681 Thank you for your reply, Sir. This really clarifies a few things that were blocking further understanding. I'm reading your book and really enjoying it. I can't do more than contemplate one concept per sitting, but I'm finding that very stimulating.
Thank for your great Video!!!
Where is the file?
Gabriel,
Which file are you looking for?
Doug Tougaw
Here it is :
Mister Mi-YAGI 😆
mi-yabi maybe ? :D haha