Radio Antenna Theory 101: what they are, how they work

Radio antennas are absolutely everywhere. We use them for all forms of radio communication whether low frequency, high frequency or for microwaves. They may be big or they may be small.

In this video I look at what a radio antenna is and give a very simplified explanation of how one works. Essentially it is the electric charge arising from the signal applied to them that gives rise tot he electric field, and the current flowing that gives rise to the magnetic element of the field.

I later go on to look at some of the basic parameters for radio antennas. Aspects such as polarisation, feed impedance, resonance, bandwidth and the gain and directivity.

It's also important to understand the law of reciprocity for a passive antenna. This means that an antenna will perform in the same way and have the same parameters of gain, feed impedance, directivity and the like whether it is receiving or transmitting.

As radio antennas play such an important part of our lives, it is important to have a basic understanding of them sot hey can be used better and the right one selected for a given purpose.

More information about counterfeit components:

[f.k.b.]

This is a great explanation! I worked for a manufacturing company who wanted to use RFID labels to check if boxes had the correct parts and quantities as they were being shipped. The issue was the parts were large, in large boxes, stacked on top of each other made of half metal half plastic. The antennas were mounted at the loading dock's entrance to the trucks. Between the all-steal fork truck absorbing all the energy and the metal shipping containers turning the antennas into satellite dishes, those radio waves bounced everywhere and were reading parts sometimes 20 feet away but missing parts right under its nose. Both the onsite manufacturing engineers (that put it in and then expected me to get it to work) and the RFID salespeople.. they were both on the same page of a magical perfect world that didn't exist.

[policedog]

Yes, I'd like to suggest Plasma Antennas. The one that I think I saw looked like a fluorescent tube but with a twisted wall shape, seemingly not symmetrical, and the tube appeared pink outdoors in daylight. It stood vertically, and appeared to have a motorized perhaps stepper motor base upon which it could spin. I thought it looked as if the partly spiral shape, when spun, would allow a moving slit in the tube to scan about a five foot vertical beam. I believe it may be a means to view at high resolution inside structures from about 20 meters or more away.

[nathanwaller]

I gave it the One thousand like, and it was well deserved 👍

[janiceemery]

Thank you for presenting this simplified form of radio antenna theory. I love it. I am trying to learn as much as I can about ham radio but, the information is so overwhelming. Besides all the theory, I am trying to learn how to solder and put all the wires together. I wish there was a book on putting it all together in a simplified form. I have no electric background so, I am having to learn all that so that I don't blow anything up or ruin my radio. Thank you so very much for presenting this video. KO4UWU

[SampleroftheMultiverse]

I am still using my outside tv antenna.
For some reason my channel 5 signal strength is lower in the daytime and stronger at night.
I remember when AM station had to follow rules on their Broadcast power based on sunrise and sunset.
Does the FCC have some rules like that for TV stations?
5:53

[ehvway]

A radio antenna is:
The interface between the wired world and the wireless world

There is just no better explanation!

Great video Sir!
Love and respect from the Netherlands 😎

[ricksampson]

I'm curious on how the various Martian rovers etc are communicating with Earth based receivers.
I have always been under the impression that interplanetary space is a noisy electromagnetic environment, and the considerable physical distances involved would require a substantial remote transmitter and antenna array.

[alanturner]

said it on X and say it again fantastic easy to follow and understand thank you

[IbrahimAhmed-dm]

Please, what is a good curriculum for my institute students? I want to teach them mobile tower (Cell towers), but my system is not ready yet. Can you assist me?

[railgap]

Radio antennas are nothing more or less than impedance matching devices, matching the impedance of your transmission line to the impedance of free space (377 ohms). The E & M fields in the transmission line, around the antenna, and in free space - are the same two fields.

[IbrahimAhmed-dm]

Thank you plz can you send me by pdf this

[ReadJohn]

John 14:21-23 ESV
Whoever has my commandments and keeps them, he it is who loves me. And he who loves me will be loved by my Father, and I will love him and manifest myself to him." [22] Judas (not Iscariot) said to him, "Lord, how is it that you will manifest yourself to us, and not to the world?" [23] Jesus answered him, "If anyone loves me, he will keep my word, and my Father will love him, and we will come to him and make our home with him.