Radio Wave Properties: Electric and Magnetic Dipole Antennae
Вставка
- Опубліковано 17 лис 2020
- An HP model 3200B VHF Oscillator and ENI model 5100-L NMR RF Broadband Power Amplifier provide a 300 MHz signal to a half-wave dipole antenna. The voltage variation along the length of the dipole transmitting antenna is made evident by touching one end of a 8-Watt fluorescent lamp. A copper rod of the same length as the transmitting antenna is used to show a similar standing wave in voltage along it. A second receiver antenna with an incandescent bulb wired in the middle shows the polarization and shape of the radiation pattern emitted by the transmitter. Finally, a loop antenna is used to show the polarization of the magnetic component of the electromagnetic wave.
For lots more details on our setup, see sciencedemonstrations.fas.har...
I don't know how to express how much I respect these demonstrations of principles which mostly consist of "theory that just works". Great work.
Do what he did: Make a video that shows your thankfulness! Maybe sing a song! :-)
If my grade school teachers had demonstrated stuff like this, I would have had much more interest in science.
That’s why we’re life long learners in our interests my friend, you can’t expect another human being to have their best interest for solely for you or their surroundings. In my not so brilliant understanding 🤕this short life for humans consists of just time and energy and which way we chose to utilize it, is to each their own
@@Ebap-dy9zpyeah but when we were kids we expected it because its what we were told. I get what ur saying but it only works once u realize everyone has been full of shit this whole time.
Your grade school teachers got their science from the textbook.
@@billfargo9616 and the Bible. Three conflicting ideologies will always create more problems than solutions
@@billfargo9616 yup
Even though one knows the theory, actually seeing the field properties is so informative, real world.
This would be a great video to show to prospective ham operators in a Technician license course.
Absolutely. The part at 3:00 where he is effectively speaking about antenna polarization, would be very helpful for newer people into Radio. It's a visible version of what db drop looks like when you're running incorrect polarization.
Yeah, here new hams operate an unlicensed transmitter at 100 watts to play with light bulbs. Whilst you're at it, get a 100 watt amp for your 11 meter rig.
this had to be shown to anyone in past decades using analog tvs who were tryinh to adjust their tv antennas :P
He didn't show his facility. Maybe he is inside a Faraday cage to prevent unwanted transmission. I mean really, 100 Watts? How does he get away with that without having the FCC on his ass?
@@ahmetmutlu348 Some of us still adjust our TV antennas.
As a Ham operator, that was not just interesting, but hugely informative to help me picture what goes on on an antenna. And just cool science. Thanks very much!
Impressive demonstration.
Safety distance of 100W 300 MHz into a dipole would be about 4 meters in my country (28 V/m E-field strength limit)
Or about a mile in the UK.
He's wearing a mask, so its "okay". (Obviously this is 'sarc'.)
The Florescent bulb is a voltage device, and so it emits more light, at the ends of the dipole, where the voltage is highest!
It's one thing to read about it from some book, but something much more digestable and intuitive to experience it in person using such simple tools!! More and even lower grade schools should show stuff like that!!!! So THANK YOU VERY MUCH! 73 !
Very nice demonstration！ THank you sir！It helps a ton to have a better understanding of the electromagnetic filed out of a dipole.
This was absolutely fascinating. Thank you so much for demonstrating this.
I appreciate your experiment. On demonstration of B-field, in fact 2 loops perpendicular to each other exist, the small loop is the connection of the light bulb. The small loop could get the B-field. In near field probe applications, we always use small loop sniffers perpendicular to the wire.
Brilliant presentation. This explains theory of Maxwell Equations in practical way.
10 years ago I saw a identical video from Harvard, I think was this same lab and transmitter, but there was a water tank and he submersed a smaller antenna that lit a bulb only inside the tank, showing that the magnetic field changes in wavelength when traveling inside different densities, so the bulb did not lit outside the tank because the antenna was so small tho the wavelength of the air.
I think you're referring to this write-up on the experiment (scroll down towards the end); sciencedemonstrations.fas.harvard.edu/presentations/radio-wave-properties
@@wolfgangrueckner7151 Wow! That's it! I read the entire page at that time... so it was not a video! My mind tricked me! Thanks to show me the page!
As an RF specialist i liked too much this video! Very didactic!
OUTSTANDINNG! Very well done. Thank you
That loop still blows my mind
Thank you so much for taking the time to create such valuable video
Even if you know this stuff it's a beautiful demonstration.
Great visual demo and explanation , very helpful 👍
I visited a high power transmit station, the fluorescent light fixtures were fitted in the room but never wired up to mains power, but they had a nice glow just like this demonstration.
Great explanation! Thanks.
Amazing presentation, thank you!!!!
As an AM broadcast engineer, I used to have visitors carry a 4' fluorescent lamp to "help me" and walk them past the tower. A lot of broken lamps in the gravel over the years.
We experiment with Lorentz force RF antennas. The physical field manifestation is interesting. Here is one setup:
1) 10 layers of store-bought aluminum foil, each layer separated by a dielectric layer (basically a 10-layer lamination).
The lamination is horizontally oriented on the workbench
2) very strong vertically-oriented B-field applied to the axis (center) of the lamination
3) roughly 16 Mhz fed to eddy current coils positioned radially, and adjacent to, but not touching, the foil lamination
With a vertical B field through the centerpoint, and radial eddy currents flowing horizontally through the metal layers, the Lorentz force sweeps the charged particles in the metal layers back and forth, coherently, at the 16 Mhz rate.
Since artificial gravity can be created by immense coherent accelerations present in the bulk of a sample, we use variations of this design to check for such effects.
It's really facinating how so many properties with-in Nature exist in waves, frequencies, and vibration, which converts into energy. Also differences seem to be a key factor in keeping dynamic systems functioning. High pressure/low pressure, hot/cold temp, different densities, static electric charges/discharges, electromagnetism north/south poles, different velocity/angular momentum, layers between different regions like land, water, air, edge of atmosphere, in space the regions of particle bubbles/cloud regions, nebula's/ Galaxy clusters/to less dense regions of space. All of these things are basic differences but create a way for the dynamic engine with-in Nature to continue flowing and operating to create and convert energy. Like regions of high/low pressure and temperature differences create winds. Transfer that into water or planets core and add density. It creates either ocean currents and flow or planetary convection geothermal activity.
In fact if you move at speed to that difference the effect disappears. All exchange of energy can only occur between non identical dynamic oscillations.( waves )
@@das250250But who, or what can actually move at those speeds?
@@MR-backup it is all relative but other particles may be moving quickly like muons .
@@das250250It can't "all be relative" if you follow up by saying there is SOMETHING "moving quickly".
Either way, aren't you just confirming the OP?
@@MR-backup Not sure what you are asking "op" ? My statement says there is only relative motion and possibly values. As per relativity.
Very interesting demonstration, I believe that it is the same emission that leads to close the dipoles of the L-rods with an electric field and variations of the unified field :-)
Superb Demonstration! Thank you!
OMG fantastic ......thanks a lot ... if such experiments are shown .....all people including non technical ....will start loving the physics,maths & nature.. .....
love these videos!
great video as always :D
Great way to demonstrate this. Thank you!
Glad you enjoyed it!
Outstanding explanation 👍 thanks for sharing.
Awesome demonstration!!
What a demonstration sr👏👏👏
Super film. Dziękuję bardzo
A co na to 6?
Thank you for this great video!
Fabulous demo !
Brilliant demo
As you I use to show this to my students (ESIEE Paris) but with the help of a Baofeng and a log-periodic Yagi. I don't have an 100 W RFPA ! But I believe you don't use it at full power otherwise the bulbs will suffer somewhat. Using an horizontal reflector below RX and Tx dipoles you can also show the Fresnel zones. All students like to see that :D
Yes the amplitude of the oscillator that feeds the power amp is turned almost all the way down, so the total output of the transmitter is less than 20 W/m^2, otherwise we could burn out the tiny bulbs on the receiver antennae :)
Thank you and more please!
One of the best videos I have seen UA-cam
Fascinating experiements! 🙄
Stay safe, regards Niels ❤💕
I was waiting for him to say “Induction Loop” and “Horizontal Polarisation” , otherwise a very visual representation, thanks.
This is really cool. Consider how you might make a similar demonstration of concepts with household or hardware store items.
Fascinating!
Absolutely mind blowing learning from this video
this is the best video i have seen til today
Beautiful. Thank you
Isn't it scary that only about 6k people watch this yet prank videos get millions?
Exactly this is what I was thinking about. I was only surprised by 6000 viewers in this video. Really, this proves what people reached😔😔
Now that scientists have become a joke and a laughing stock they'll get more views, I'm sure. The dumb masses just love these cosplaying clowns and the pranks people like Fauci play on them.
Yes one is interesting and funny and the other is boring and of no use to me. I leave it to the people that want to know about this to enjoy, but don’t judge me butthole.
"Isn't it scary"
Yes, it isn't scary.
It's because small things amuse small minds..
I REALY LIKE IT! GOOD JOB
This is forcing me to think and improve my antenna - and hang a few more. Thank you.
wow, never thought antenna would be this simple
so much better than only a text book
Very nice and inspiring.
Amazing sir 🌟🌟
wow, great video.
Respect, very helpful!
Resources online today.. omg.. double thumbs up !
WOW. Spelled W.O.W. GR8T demo. This explained a lot.
Thank you so much!
No need for 100W.
I did the same when I was a eenager experimenting with approx. 8-10W @100 MHz, (with QQE03/12 tube, parts from old tube radios and TV’s and a standard FM radio dipole, Then dimming the light by varying the power.
Once light up one could walk pretty far away with the tube. It convinced my parents I could do magic. :-)
This brought back the memory of those fun times.
Correct, 100W of output would easily burn out the type 47 (1W) incandescent bulb in the receiving dipole at 1 meter distance, which is why we use the minimum amplitude setting on the HP oscillator. Thanks for watching.
NICE VIDEO!!!
COOL !! 😀👍🏻
Thanks, Bro
This is a very cool demonstration! Can you come up with an experiment that reveals the phase relationship of the electric field to the magnetic field close to the transmitting antenna? I'm interested in an experiment, not in a variety of equations. Thanks.
If you had an oscilloscope I think it could be done? It is an interesting idea as the fields at far distance, electric and magnetic, are in phase while near the antenna there are parts of the fields that are 90 degrees out of phase. You would need tiny examples of the test probes used in this experiment, a small dipole receiver and a small magnetic dipole receiver connected via coax and connected to the oscilloscope with equal length leads you could then see the phase relationships? Please make a video as I don't have an oscilloscope. Thanks.
@@andyeverett1957 I have wanted to make this kind of measurement for awhile. Have never gotten around to it ... maybe I should revisit this test having acquired several vector voltmeters as well as several dual-trace scopes ... I also contend that the traditional; dipole antenna works on the principle of the magnetics (magnetic field) to create the 'radiation' and not the magnetic ... not even the combo of the E and H ()or B) fields - JUST the H field.
Beautiful go on i love science
I love that video :)
Thank you so much ❤
I feel like that's a bit too close to be around that antenna at that power output...
Lets not forget 300 watts of electromagnetic field is being pumped out from that dipole antenna.
Has no effect on you as 300MHz is a very long wavelength.
@@ShopperPlug Stand under a transmission line and you have megawatts of 60Hz EM radiation.
Neither has any effect on you because the frequency is too low.
@@t00by00zer yea it’s somewhat true that strong electromagnetic fields does not have much impact to humans, but I’m not convinced, there is not enough scientific data suggesting strong electromagnetic fields is 100% de-facto safe.
@@ShopperPlug It's not the field that gets you. It's how fast the field is vibrating that gets you.
Standing next to a 10 megawatt, 60 cycle transmission line has no effect on you. Change that to a 100W microwave and your skin cooks.
It's all about the frequencies and what they in turn resonate with in your body.
Well attractive explanation, thank you.
Thank you sir.
Thank you very much for this educative video and visualise the antenna field surrounding it.
Tnx for sharing VU2GNR
It would be fun to build an array of lights and coils along the dipole emission field in 90° orientations to see this effect. thanks for sharing
That was brilliant. I bloody love the Internet.
Amazing!
This is great
This gives me bumps, geting back to that tesla photo holding a light bulb
Magic demo.
Gracias.
Most excellent presentation! Seeing the relationship between linear dipole and magnetic loop orientation for maximum current flow is critically important; I’m trying to design an antenna with the inductive sensitivity of a magnetic loop yet able to reflect and direct the electric field aspects of radio signals the way the capacitive character of the linear dipole is able to accomplish. However I’m not able to “see around” the fact that the magnetic field is 90 degree perpendicular to the electric field which is oriented in the direction of wave propagation...an essential fact for electric wave reflection.
Do a search for 9A4ZZ bipole antenna. It is not short dipole, it is instead an E-field two-pole radiating structure ... especially look at radiation pattern. Minimums off the broadside whereas dipole HAS max off broadside.
It is a very nice demonstrations supporting antenna theory, will it be possible also to perform similar demonstration using folded dipole instead. Thanks.
well done
Yes, very nice, thanks.
That's some cool old school Tesla OG there
Sus videos son muy buenos siga asi
Excellent superb. Tq
great demonstration
Super cool
I love your remarks and, if you brought a circular antenna and take it to a spin, I'd love to see what it does. Because you, it's on a linear point of view. . .
J'adore vos remarques et, si vous apportiez une antenne circulaire et que vous l'emmenez à une rotation, j'aimerais voir ce que cela fait. Car vous, c'est sur un point de vue linéaire . . .
Excellent demostration. Educative and very useful. However I have one doubt. Why the bulb in the receiving antenna didn't glow brighter when the same is brought in line with the axis of the main antenna?
Thanks. If your question has to do with the signal attenuation that happens at around 3:28, it is because the transmitted signal is minimal along the axis of the transmitter. Think of the pattern as shaped like a big donut (toroid), with the holes pointing in the same direction as the axis of the transmitting antenna.
Very interesting
I want a 100W transmitter too, it would be fun to use lol
Yeah you'd be in jail before you can even power it up
I get the feeling Nikola Tesla would have enjoyed seeing this.
Absolutely correct
I have a feeling that he has seen this, way before this professor was even thought of!👍
Actually, Tesla is the Father of all this science, on paper.
@@dabig_guy2204 yes, I thought so!👍🇺🇸
Tesla never seemed to have gained the insight for effective physics for transmission. I'm thinking that's where Marconi stepped in and received credit for invention of radio communication.
Best video ever …
lovely bro
Thanks
I love this stuff
Good demonstration. That's what Nikola Tesla wanted to achieve, to be able to transmit power thru radio waves and light up the world!
I believe he was way ahead of his time!
And nobody wanted to finance his idea, because everyone with an antenna could receive the energy and you had no way to charge money for it.
Not wanted to achieve, he did achieve it. It's the world that stays stupid
@@Laienhaftes well no, since you'd need special equipment to get the power and turn it into something besides sound. So the hardware would cost money.
@@josephhacker6508as soon as you have the equipment to receive the power (and that's very easy and cheap to achieve) you can consume power and the transmitter can't tell how much you are consuming.
@@Laienhaftes Totally wrong. Transmitter detects a load.
Tesla's idea was flawed in many ways and that's the reason why it never lived in the way he imagined it. Not because of some conspiracy.
So to me the next step would be to capture any electricity and store it. Can that be done? Or can it only provide a throughput to the load? And if electricity can then be captured from the B-field antennae, can it be scaled up to the point that it produces a significant enough amount of electricity to power electrical devices or even a home.?
How far away can the receiving antenna “receive” and what can be done to amplify the signal? Didn’t Tesla try building a large antenna to produce “free” electricity with similar technology?
And what’s more what is the impact of high frequency signal on human body and also why is the efficiency of wireless power transfer.
what the happen if i have many Antennae ring nested
I’m trying to learn about dipoles and landed here. Great video but would the results be the same if the poles were sideways Up/Down direction which is what I thought was the direction they should point to? If a dipole can be used in the same direction as your video what’s the difference and why?
the near field geometry of the dipole field will move with the orientation of the dipole antennae. If you've ever seen a shortwave setup, you'll see antennae with both vertical and horizontal orientation. Depending on the band and conditions, each orientation has its uses.
What matters is matching the orientation or "polarity". The voltage reverses 300 million times per second in this demonstration and that produces a wave in space that moves left to right to left to right (or up and down if it was oriented that way). This wave can excite the electrons in the antenna IF the antenna is oriented the same way.
WHILE the electrons are shuffling from one end to the other, they produce a magnetic field but only while they are moving; but produce voltage when they pile up at the end. So maximum current and magnetism is in the middle of a dipole, maximum voltage at the ends and it can be lethal to touch the ends but relatively harmless to touch the middle. I still wouldn't do it, there will be about 50 volts at the middle but maybe a thousand volts at the ends.
For radio purposes (communications) shorter range communications tend to use vertical antennas mostly because of physical constraints; you get an omnidirectional (equal strength in all directions) which is fine for driving in an automobile. But a dipole has some directionality and if you stack dipoles you get a Yagi antenna which is directional and will greatly increase the distance of communication.