RF and Antenna Basics in 802 11
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- Опубліковано 16 вер 2015
- This video is intended for those looking to learn the basics of RF and antennas and how they apply to 802.11 wireless systems. No prior RF knowledge is required. Explanations have been simplified in the interest of conciseness. The link for the full course + exam is here: www.udemy.com/course/rf-anten...
- Наука та технологія
This video is abnormally informative. Never expected that such a clear explaination exists on internet.
This is, by far, the most informative and interesting presentation on 802.11 I have found. Excellent illustrations and video/audio quality. I hope you make more videos on similar subjects (like 802.3). Thank you!
Hi Eric. Thank you very much for your comment ...it really made my day. I have had to address many of these principles over the course of my career, so I figured it would be best to put everything into a video that could be shared. Cheers, -Hank
@@hankottey338 hi,...i just posted a question just below the video....either you or Eric, could you explain it please?
Best video explaining antenna basics i found on youtube yet.
This is a superb presentation. It is relevant to most of the important factors that need to be taken into account for clear radio signal transmission and reception. My compliments to the author.
Thank you very, very much, Peter. I really appreciate the compliment. This was surely a balance between simplicity and complexity in terms of conveying everything that goes into signal transmission and reception! Thanks!!!
By far the best video out there on RF. Thank you.
Thanks, Jon! So good to hear comments like these. Thank YOU! -Hank
Fantastic production thankyou Hank I was bored to tears with CCNA Wifi but this nugget cleared up alot of doubts and and made everything simple. Brilliant.
Wow, that is quite an endorsement, Mike -THANK YOU!!! I did try to make this as interesting and enthralling as possible, while doing my best to keep it simple. Comments like these are very reassuring in that respect!
Amazing video, its fast pace makes it very interested to watch and learn!
Thanks, Salar Yunis!
Thank so much for making this video, Hank! The quality and clarity of your delivery is absurdly good! I had so many moments where I was like "AH! SO THIS IS HOW IT WORKS". As an EE student, I hope one day I can achieve this level of presentation and technical mastery!
Thank you so much, @vma011! I am very glad the video helped you. Thank you for your compliment, too! All the best! -Hank
Fantastic video. Thanks mate! It clears a lot hard to visualize things for beginner.
very good presentation
Thank you very much Sir, it was really a bliss to listen to you. You presented many compex concepts in the most simplistic way.
thank you! most informative rf video for those with no prior knowledge
Glad to hear this, ryan smith! Thanks for commenting! -Hank
simply awesome...great graphics and easy to understand explanations.
Thank you, Vishal! I do try to make the explanations as plain as possible, and put as much effort as I can into the graphics. Glad you enjoyed! -Hank
So clear explanation Hank
Very good explanation. Illustrated and good examples. Congrats
Thank you very much Carlos Henrique Biscuola de Souza
!
Very pedagogical work.
Much appreciated, aavellancursos!
The best video on Radio frequency atenna , you cut all the webs surrounding the complex Antenna topic ,the way inerference and signal lobes was explained ... mind blowing....
Thank you very, very much, Avinash! It really made my week hearing such a flattering comment. I tried to simplify the concepts as much as possible in order to make them more understandable. I am so glad you enjoyed it! THANK YOU!!!
Fantastic Video. just watched it all. a great tutorial and very well done Hank.! just subscribed. you are a great teacher with impressive presentation skills. It was a pleasure talking to you today. keep posting more videos. looking forward to them :)
by the way i missed asking, have you explored mounting a 3dBi antenna for mining crypto? :) i have one on top of my house. i can talk to you about it in our next conversation.
Excellent work!!!
Seriously awesome visuals.
Thank you! I try to put as many pictures and animations as possible into the technical explanations, as they seem to be so much more effective than just words.
One of the Best..Waiting for more : )
Thank you, EC!
Thank you!!! Best explanation.
Deep and informative..plz upload video on Network KPIs..thank you
This is one of the best presentations I’ve seen on the topic. Thanks and keep them coming.
Thanks, CG Ruiz. This means a lot!
Excellent work.
Thank you, Nilesh!
@@hankottey338 hello, i am trying to find some information about Folded Dipole antenna. I have information about Dipole and that two poles are not physically touching each other. So there is a electric isolation. But in Folded antenna, two poles are touching. By a folded part. Now, if the charges move in one direction in two half parts ( half parts mean a part where you connect your supply wires ), then the same charges will move into other direction into folded part. Then the em wave emitted by both the parts will nullify each other. Don't understand. In some pictures i was shown that the charges move into same direction. How? I wish to send you that picture. How can I send? I need email address. I can not attach here.
Please explain.
Very informative! Thanks.
Good video ,are there any other AWP videos
Great video! Thanks for sharing! :)
My pleasure, Neil Arellano!
Very good video. I am a former 31C2 and a Ham Radio Operator and the information is very accurate and the presentation is excellent.
Any more videos coming soon ?
Hopefully, yes and soon !! 😉
Realy .. a HAM you say
Accuret you say
Are you delutional !!
Ther is No ISOTROPIC ANTENNA
Or EIRP IT's fiktional
Thank you very much, F TR Competitor. That is quite a compliment coming from someone like you!
the best course
THANKS SIR. I GAINED MUCH.
My pleasure, sakthivel Periya Muthaiah. Glad the video helped you!
Thank you for this lesson
You are quite welcome, P F01!
Great video!! Thanks
My pleasure, Ruggiero Guida. Glad you enjoyed it! -Hank
great tutorial, any more coming soon?
Thank you, Sherjeel. I was considering doing a video on wireless network optimization. Thank you for the compliment. It is always nice to hear these! -Hank
Excellent video
Thanks, Ricardo. Glad you enjoyed it!
Hank Ottey hands down is the most complete "wireless basics" video out there, do you have any plans to make more?
Hi Ricardo. Wow, thank you very much! I am quite flattered! Sorry for the delayed reply, as I just now saw this message. I do not have any plans to make more videos on wireless, as I am currently working in a different field. I did enjoy making the video, and do look forward to making other instructional videos. Please feel free to connect with me on LinkedIn (www.linkedin.com/in/hank-ottey-8aba88). Best Regards, -Hank
clear and intuitive explanation.
Thanks
Definitely my pleasure. Thanks for watching and commenting!
Great video Hank can you recommend some books on RF and antennas?
Thanks, B c! I cannot say I have any specific recommendations for books. I am personally a fan of searching UA-cam for specific videos on related RF/antenna subjects. For example: "diffraction", "propagation", "amplitude", "beamforming", etc. -Hank
very good video! thank you!
My pleasure, Erik. Really glad you enjoyed it!
A spin of signal in space, signal multiple times of sattilite in part data, not whole data,so we broadening receiver's over district distance, a part of data only missed circle wave whole data. John.
Well done Sir. Liked.
Thank you, gex geko!
@29:11 is this what happens with our phones? when connection is good(higher connectivity), it uses less power, and when it is bad, the transmit power increases(as connectivity rate decreases). I've wondered why my phone dies so quickly when its searching for service. Correct me if I'm wrong.
Hi Alexander Koran. Thanks for the comment. This is likely the case, although, I am not familiar with the specific chipsets used by every cell phone!
Regards,
-Hank
Do you think a monopole antenna can be designed to detect a 100hz sine wave with a length of 40-50 cm?
Hmm, maybe in another universe ;)
@@hankottey338 :)
Regional transit quick, use simple sign prgm, to focused data, the computer of common sign lites, too transmitters many camera sites over land mass spectrometer speeds of noticed objects. John.
Help to rearrange angle to sky of orbital speed of objects recalc time, hr,min,sec, main time window,43 mins ,only til open again. No sign signal time, to data links, cold -158 C. Or 158 C hot, in90 min,orbit, John.
Is the PowerPoint available for download?
Hi Tyler, thank you for inquiring. Unfortunately, the PowerPoint is not available for download. Regards, -Hank
something is not clear.
so, the electrons in the vertically polarized antenna (electrons oscillating vertically in TX) generates a magnetic field perpendicular to the antenna (in this case in the horizontal plane of TX).
when the magnetic field from TX hits other metal metal objects (other antenna) it generates the electrons in the other antenna (in RX) moving up and down.
Now, at 4:55 he says "the oscillating electric fields hits electrons in other metal objects...it forces those electrons to oscillate as well."
my question:
what forces the electrons to oscillate in the other (RX) antenna? because now i got 2 indications from the video.
1, the magnetic field from TX
2, the electric field from TX
Can someone clear this up please?
Hi needsomehike. Sorry for the delayed reply. Hopefully I can provide some clarity regarding your question. First of all, the magnetic field is generated around the antenna (as opposed to "perpendicular to the antenna" ...see the 4:14 mark). In addition, this generated magnetic field has a corresponding perpendicular electric field (see the 6:20 mark). The two fields represented here comprise an electromagnetic wave.
To answer your question: "what forces the electrons to oscillate in the other (RX) antenna?", the best answer (in my opinion) is the electric field. In the case of an electromagnetic wave, it could be said that both fields cause the oscillation since they are one and the same when in this form. However, if a separate electric field (say, a stationary electric charge, as produced by a single electron) was introduced in the location of an antenna, this would have influence on the electrons in the antenna. In this case, there would be no magnetic field present. I hope this clears things up! -Hank
I use RF at 13.56 MHz and 27.12 MHZ in a probe about 3-5 thousands in diameter placed inside of a hair follicle to create the heat necessary to destroy the cells that cause hair to grow. I want to know specifically where the heat is generated on my probe (antenna) (tip? where the probe touches the moist tissues? etc.?) and when is an insulated probe unnecessary or necessary. I do not want the surface of the skin damaged though I want the deeper layers of the skin heated by RF electromagnetic movements to approximately 127.5 degrees F. What books can I look at to learn about the physical characteristics of the probe(antenna)? What books can I look at to better understand how the physical forces are being manipulated by the probe and the oscillator behind it to not do damage to the outer layer of the skin?
Hi Juli. Thanks for reaching out. This particular application of RF is quite different than what is used in the broadband wireless world. Generally speaking, there are two ways to go about finding the answer your question: theory, and actual experimentation/testing. Ideally, a thermal imaging camera would work in this regard. Of course, it would have to give a suitable resolution for something so small! Good luck, and thanks again for reaching out. -Hank
Thanks. I kinda knew the answer could be debated through theory and actual experimentation but where are the books on the theory? There are manufacturers of this kind of equipment who say their information is proprietary but this, to me, only means they don't know. Obviously they know that the oscillator produces the negative and positive charges at a given MHz range but from there they state wildly contradictory remarks about what is actually happening in living tissues/follicles being treated. We can see heat expansion where the probe is placed but we have no way of seeing the 13.56 million or 27.12 million per second movements in the tissues. We have no way of knowing the temperatures inside of the tissues. Where are these engineer/designers of this equipment getting their information for their design? I don't believe any of their claims for privacy are proprietary because this equipment has been in use for more than a hundred years and sold by many manufacturers who know little to nothing about human physiology/dermatology. Thanks for the tip about a thermal imaging camera. Finding something that measures at a 1-5 thousands of an inch will be difficult, especially considering the treatment is going on from anywhere from 1 to 6 mm underneath visible skin surfaces. Let me know if you are aware of any human or printed expertise that could help to continue my quest. Also, if you are aware of any research institutions with the necessary equipment and research design experience please let me know. Thank you. Julie
@@juligrlee
You might find the answer to this in books or articles on medical physics. It is not my field so I don't really know. By the way this video is a good complement to physics knowledge about radiation and patterns (I am a Physics professor but I learned a lot from this video).
@@hanksnow5470 I just now saw your comment. This was very nice to hear! I try to give technical explanations a "start-from-zero" approach whenever possible, which often means going down to the raw physics. Since my background is also in physics, I surely take this as a high compliment. Thank you very much and feel free to find me on LinkedIn. -Hank O.
Please reply i have subscribed to you. Pause
12:54 at this time when these two wires are separated with a little distance between them.
Quez1. How the start point and end point of both of the wires are connected with power source if there is a gap no connection between the top of both of the wires.
Ques2. Compare that thing to right hand thumb rule. As you told if current flows in downward direction in both of the wires it must make fields as our hand fingers you shown earlier but you have shown it like semicircle. How yrr i am a lot of 😕 confused with a lot of things of science like in a transformer the one end of its coil is given to our mains and one mid of the coil as neutral. My question is why the current doesn't go from neutral first because when the circuit is completed when the current is flowing from main wire it will get back to main only as it is A.C the current will come from neutral to main. But why not directly. Second why whole science is going in wrong way that the current flows from positive to negative but it goes from negative to positive what the hell yrr. I have maken one rule only practical science.
Hi Tusshar, thank you for subscribing!
Answer 1: The wires (antenna elements) are connected individually to the source that drives the current in each wire. This is not shown in the illustration, as the intent is to speak about the propagation of the waves, and not necessarily the construction of the particular antenna.
Answer 2: I am not sure I understand your question. In regards to the "semicircle" you mention, I am assuming you are talking about the 12:44 point in the video. The "waves" mentioned here represent the magnetic field (and corresponding electric field) that propagates from each antenna element. In actuality, the magnetic field spherically from the element. A cross section of this sphere would be a circle. I have only drawn half of the cross section of the video, so it appears as a semicircle. ***Please note that the strength of the magnetic field is not equal at all angles from the horizontal direction of propagation from the element. This is what is explained starting at 11:27 in the video
I hope this helps, and thank you again for subscribing! -Hank
You need to think of conventional current flow then using the right hand rule.
Hi slap_my_hand. Thank you for watching, and for the comment. I am not sure what is meant by "conventional current flow". Does this mean there is also an "unconventional current flow"? If so, how is each defined?
In either case, the fundamental laws of physics would still apply. Specifically, Ampere's Law (magnetic field resulting from electric current) and Faraday's Law (an electric field produced by a changing magnetic field) are what is dictating the mechanics in this situation.
Here are some links that give a breakdown of each law:
www.maxwells-equations.com/ampere/amperes-law.php
www.maxwells-equations.com/faraday/faradays-law.php
Thanks again! -Hank
@@hankottey338 Conventional current flow points in the opposite direction of electron flow. In an electeical circuit, it points from the positive terminal of the power supply to the negative terminal. A lot of things in physics are defined with positive charges, including the direction of magnetic field lines. So even if there are only negative electrons in a wire, you think of the movement of imaginary positive charges when you are working with conventional current flow.
thank you!
You're very welcome, Alexandr Petrov!
nice one
After 4:35: The original movement of the electrons is not caused by the movement of the magnetic field, but by an alternating-voltage-source.
Hi Jacob, Thank you for the comment. -Yes, the original movement of the electrons in the transmitting antenna is surely caused by an active mechanism (alternating voltage source). In the video between 4:35 and 5:11, the receiving antenna is shown, which passively receives the waves (alternating magnetic field, and corresponding alternating electric field) created by the transmitting antenna. I hope this explanation makes sense. -Hank
@@hankottey338 I thought it was a usefull remark to make.
In 32:47, I am worry that there is wrong placement. Fade Margin (FM) is lower than the received signal. So, in that case, the received signal should be -74dBm while the desired signal (as per design) is -56dBm. Then, the FM is -18dB. And look! The unit you put also wrong. dB is only for gain, not for reception or transmission.
Hi Sitorus,
Thank you for watching. I certainly appreciate feedback on the video.
In regards to your comments, I would like to clarify the origin of the signal values. The "-74dBm" is from 29:33. This is the necessary minimum received signal strength, in dBm, that is needed to achieve a connectivity (data rate) of 54 Mbps for 802.11a. The "-56dBm" is the resulting received signal from the system described in 32:12. The fade margin is the difference between these two values (-56) - (-74) = 18 . By definition, the fade margin cannot be negative. In other words, if the received signal is weaker than the desired signal, the fade margin does not exist.
Regarding the units, good catch! Although the technically correct way to write the units of the equation in 32:33 is
"(-dBm) - (-dBm) = dB", I feared this might be confusing to someone who is just learning RF, so I gave the equation a simpler look by labeling all values as "dB".
Finally, the correct unit for antenna gain is "dBi" (decibels relative to an isotropic radiator).
Please let me know if I can clarify further, and thanks again for watching!
-Hank
Thanks for the info but sorry to say that the music in the background is really irritating. You should take that out.
Hi STATIC-SHOCKER. I have to agree with you on the music. It certainly would not be my first choice, but I was quite limited on the selection of free music with which to compliment the video when I made it. Hope you liked the video otherwise :) -Hank
vektor-- lighted use, of a tiny hammer-- medical.
Nama :
There are many inconsistencies with even the basic concepts. As a teacher I don't recommend to follow this video for any antennas courses.
Thank you for your comment, -- . Can you state the exact inconsistencies? Please do let me know, as I would like the video to be as accurate as possible. Thank you!
There was an ambient noise in this video that weaken the strength of the content. The back ground music did nothing to enhance the video and did everything to distract from what you were saying. I couldn't make it past 3 min. Sorry, but I hope you have rethought this approach.
Thanks for the feedback, Ross Hollinger. Always appreciated, good or bad! I have taken your advice and made my latest videos without background noise. Cheers, -Hank
9
This Will newer ever work
Becaus you aculey don't know anything
About the things you talk about
Why Will this not Work !!! Ther is No ISOTROPIC ANTENNA or EIRP
IT'S ALL FIKTIONAL !!
There's no electron! Metal is, what gives off-- energy.
87 kali
Your stupid background music is both annoying and unnecessary. It distracts from your excellent commentary.