Antenna-Theory.com Presents: The Dipole Antenna

[@johncgibson4720]

Love this video dearly. No other lecture or presentation is nearly as good as this one. This is god level comprehension from basic Maxwell to the end application in the neatest most concise manner.

[@codijack9577]

The easiest way of antenna explanation what I ever heard - great!

[@mereldawu]

You lectures Really well, I finally know why our lecturer draws a dipole like that... Thanks a million :)

[@Akileze]

Thanks for taking the time to present this information. I was lucky enough to work in telecom (analog/digital radios/muxes/switches) when you still had to kind of know what you were doing just to setup the test equipment properly. The computerized stuff started showing up (no more tweakers..yawn) and the fait accompli was the shift to on/off keyed lasers that a child could setup. Bored to tears I moved into management for something different (it was that ;-) Thanks again...very good stuff!

[@SteveWrightNZ]

At 7:40 shouldn't one of those lobes be underneath the antenna, indicating opposite polarity? Thank you greatly for your very interesting and useful training.

[@BananaJSSI]

Excellent video. I have many antennas over the years and currently I was thinking about getting a Dipole.

[@durragas4671]

7:00 "fattening up" can also mean making a loop? I remember some TV antennas having loops like that.

[@ElPasoTubeAmps]

I really enjoy your videos on antennas. But I have a question. Since the half wave dipole is inherently a 73 ohm antenna why are we always trying to match it to our 50 ohm transmission lines by feeding it in the center? Can we change the feed impedance by shifting the feed point to one side of center like the slot antenna or would that always increase R or increase X to an unmanageable point? Telling me to feed it with 75 ohm coax for amateur radio HF work is not an acceptable answer as we love our LMR 400 and such. I am sure you know this. We use mostly current baluns or just a coax choke at the feed point and do the best we can to trim our antenna to resonate to keep the SWR down and then use an antenna tuner to keep the transmitter happy and all-in-all it turns out pretty good but what really got me to thinking was your video on slotted antennas. Thanks again for taking the time to share your knowledge on antennas.

[@redknight344]

i think is because the middle of the antenna is the lowest imput impedance we can get so if you move the feed the real part of the impedance only gets bigger so no 50 ohms anywhere.

[@KevinAshcraft]

This is how I learned the basic details of dipole antennas. Thanks for the free info!! #hamradio

[@coffeecuppepsi]

so... would a full-wave length antenna be suitable for receiving? if we have high impedance into the tunned tank circuit the high impedance of the antenna won't destroy the Q of the tuned LC ?

[@tag_of_frank]

Can you recommend a textbook specific for antenna analysis?

[@pjbevel]

What section are you referring to?

[@ScientistPrepper]

Super great explanation. This guy should be or hopefully is a teacher. Thank you.

[@18micky1991]

nice..... plz te;; me the app you were using or any other app for dipole, folded antenna or radars etc

[@pjbevel]

No, current and voltage still follow a full sinusoidal wave along the transmission line - with maximum and minimum separated by a half-wavelength, so a full period is one wavelength

[@gamersanonymous4790]

Did you study Physics to learn this or Signal Engineering? I find all this fascinating

[@johncgibson4720]

He is most likely from an Electrical Engineering background. I doubt Physics majors look at the impedance of antenna because impedance studying is an optimization. Impedance itself is very simple if you only look at circuit itself. Antenna is also very simple if you don't consider impedance problems. But when you put circuit and antenna together, a large swath of human population can not understand it for the life of their time. Same goes with the quantum/general relativity incompatibility problem.

[@methods-SE]

Start with Electrical Engineering, heavy in math. Pete has a natural talent, so don't expect it to come easy.

[@fredkelly2645]

hi can you tell me why a dipole for 2.4ghz has a 1/4 shield - wavelength then a 1/4 element + wavelength then a coil (5 turns) then a 1/2 wavelength. something like this IIIIIIIIII----------((((-------------------- how does this effect the positive and minus?

[@godfreyhamshire]

Thank you very much I learned a lot from your video thanks for sharing the knowledge with us.

[@tonipassioni]

Very thoughtful of you to reply. '73, Hal

[@sanjaytumati]

Hi There, Enjoyed your lecture. A question about the charges. You mention build up of positive and negative charges causing electric fields. The negative charges are easily understood as electrons. What are positive charges? Positively charged Ions? In a conductor?

[@redknight344]

no, just represent the lack of electrons of that area and the electric potential that is created by the negative charge acummulatig in the other corner

[@puneethprahalad7386]

4:16 instantaneous Electric field direction is downwards I believe. But yes, that’s the polarization. Good video 👍

[@Starbuckin]

Excellent Dipole analysis! I've already built one for 20 meters. It is about 65 feet in length (half wave resonant at 40 and full wave at 20) and have talked all over the world on it on 40, 20, 15, 10, and 6 meters with 100 Watts. It also works on 80 meters. I am using a MFJ 969 Antenna Tuner. By your analysis it should not work on 20 meters, since it's (approx) full wave resonant there. Any thoughts? It may be the 300 Ohm twin lead I'm feeding it with has some positive effect?

[@subramanianr7206]

Yes, you are right. The full lambda antenna is fed in the voltage node which implies very high impedance (in the order of 1000s of ohm) You can not use a 50 ohm coax cable to feed here. Any open line (300-600 ohm) along with a genuine BLT (balanced line tuner) would do the job very well. De VU2RZA

[@davidbee3704]

Left handers should write/draw from right to left, that way we can see what you are drawing/writing as you do it. Fun fact: Leonardo da Vinci was left handed and wrote backwards (from right to left) so he didn't smudge his writing. Thanks for the video. 👍

[@zeroxero111]

isnt the max to max difference for the standing wave actually meant to be lambda/2 not lambda

[@sepphuber7434]

As an electrical engineer not specialised in RF I was always looking for antenna stuff that is not too basic, but not too theoretical either. This is great stuff! However, one thing I did not get: How does power get to a half wave dipole? You explained in other videos, e.g. about the slot antenna, that power does not get to an antenna when either current or voltage are at a minimum at the feed point. At the feed point of a half wave dipole the current is at a maximum, so the voltage should be at a minimum and thus no power should get to the antenna. What am I missing here?

[@redknight344]

as you said, in his video of the slot antenna he said you can't feed the antenna in the middle because the impedance appears infinite but in reality is too high, and this is because the current is 0 but in this case the impedance goes to 0 but in reality neither is 0 in reality the value is aprox. of 73+43j ohm, that is the lowest value the imput impedance can get, and this is because the mathematical model of the current distribution and voltaje presented here is not really the real one is an aproximation thats why in the slot antenna the real impedance in the middle is not infinite and here is not 0.

[@bereketketema1077]

did you work some campany/

[@zeroxero111]

I was referring to The transmission line part towards the beginning , the antenna part is fine

[@n4lq]

Did I hear you say a 2, 3 or 4 wavelength dipole "will not radiate"? Surely it was my ears!

[@pjbevel]

I explain why directly following that statement, what is the confusion? If you feed a perfectly symmetrical thin dipole that is an integer multiple of wavelength, no it does not radiate because of the impedance. Same reason you can't feed a patch from the center....

[@johnjeremias9997]

thanks enjoyed video; very clear explanation. Congrats!

[@KILCOLEMAN616]

Impedance is something like 73+j42.6 - a number rough number off the top of my head?:P

[@santureoo]

Why L=0.48*lamda not L=0.5*lamda ? thank you

[@yogipg2022]

My guess is for any given frequency to reduce the inductance of the antenna so that the total inductance matches the capacitance and the antenna becomes resonant. Somebody let me know if that's not the case.

[@pjbevel]

There's no video that will be perfect for novices and people with technical background. But if you want more information on antenna definitions and key terms I have this available: antenna-theory . com and click "Antenna basics"

[@FlyRussiaFromUSA]

Thanks for sharing!

[@sleeve8651]

Succinct ! Sorry I'm late to the party ! This is fascinating ! Best ever ! Thank you ! 👍😉

[@pete463251]

No Problem. What stuff was over your head? Maybe I could explain it in a different way

[@Rajendra12387]

Thank you !

[@bocarly354]

Thanks sir for sharing this wonderful videos and from it I learned a lot. Furthermore, can you please make a videos on the type of antennas used be implanted for medical devices. Once again, thank you sir for sharing ur knowledge

[@jacobvandijk6525]

@ 1:02 Currents in a wire flowing in opposite directions??? in my opinion, this has never been observed in nature, but in Pete's world everything is possible. Pete likes to keep things simple for himself. KZbin shows the best of mankind. Haha. This looks more like it: kzbin.info/www/bejne/Y3eafIyChJl1ock

[@peterb7615]

always great to hear from a fan! thanks!

[@jacobvandijk6525]

@@peterb7615 You're welcome. Keep on confusing people, mate ;-)

[@kevinrtres]

Thanks, that's an Excellent reference - much better explanation and so much more understandable.

[@jacobvandijk6525]

@@kevinrtres You 're welcome. Good luck!

[@XPSTECH]

thanks for the video...

[@beeftimer]

Total length: you have it drawn with a significant gap between the two gaps; is this part of the total length, or is it just the added lengths of the two ends? Low efficiency and low bandwidth for small antenna... why??? 1.76dB... Z = 73+j42.6... where did these numbers come from? Where's the math? Where's the explanation? Isn't that the purpose of this video, to explain these things?? 90% efficiency/ 7% bandwidth... same thing. Where are these numbers coming from? These are very specific numbers, yet there's no math or even any explanation explaining them. I think answers to these questions should be given in a video like this for it to be of any value to anyone, but I guess that's just my opinion.

[@NMP1]

Nice! thanks

[@narinpornwatcharakul6237]

Concept key for antenna theory see at www.facebook.com [Concept key]

[@chriswesley594]

Jeez So many comments about the clarity of this video, yet it reminds me of my worst lectures at university. Spoken by a very smart guy who already knows it all and has forgotten what's it's like not to. So it's fuill of opaque terminology which the people watching this video will by definition, probably not understand. I have a degree in electronics (though not in antenna or radio) and having watched this video, I have very little idea of what he's talking about.

[@pjbevel]

always great to hear from a fan - thank you for the kind words!

[@thestranger2749]

@@pjbevel I'm studying antenna propagation, so at least i appreciated the video. I can't imagine someone watching this video without having some idea of what you're talking about.

[@Muhovc]

In case you're studying antenna propagation, i've got a good question for you: If I connect my Voltmeter to the middle of this dipole antenna, what will I see and what does it mean (and why is it not voltage)?

[@thestranger2749]

@@Muhovc Well i can't give you any numbers on the voltage. But i will say that the current is higher at the feed point and the voltage nigh infinite on the ends. So we feed the dipole in the middle to have lower impedance that we can more easily match it to 50 ohm coaxial line. (i think the ohmic resistance at a straight dipole feedliine is around 73 ohms purely resistive non reactive) But in case you wanted me to explain it in terms to prove i do have some understanding of it, the electron flow is limited by the capacitance of the aerial elements, and since only at high altitudes is air conductive enough to allow electron flow, the capacity is limited to the metal conductor in which current is flowing until the voltage potential is too high to feed without a transformer balun.

[@redknight344]

​@@thestranger2749 "voltage potential is too high to feed without a transformer balun" what are you referring to? you start talking about capacitance and ended with another thing that is not related and then said that when the voltage potential is too high you have to use a transformer balun? excuse me? you use a transformer balun for two things match the impedance something that ONLY depends on the geometry of the antenna and where you feed the antenna and second, to get a system from balance to unbalance so it doesn't matter is the "voltage potential" is too high if you are feeding in the middle of a dipole and your cable doesn't have a 70 ohm impedance you have to use a match element to get a high power efficiency and then if the cable you are using if unbalanced like a coaxial cable you have to use the balun for a very similar objective, to get a high radiation efficiency, so neither both things are affected by a "hight voltage potential".

[@TheArtificiallyIntelligent]

Uhhh... I think I need to watch some other videos before watching this one.

[@4ANIRUDHA]

this guy hold pen just like me :)

[@tonipassioni]

not for an inexperienced person. Key terms not defined.

[@rafflderchef]

why do americans always ask the things when they explain it?

[@amairabdullah6248]

boring