Antennas Part I: Exploring the Fundamentals of Antennas - DC To Daylight

Summary

In 'DC to Daylight,' Derek explores the fascinating world of antennas, discussing their role in transmitting and receiving signals across various frequencies. He explains the relationship between frequency, wavelength, and antenna size, and how lower frequencies enable long-range communication. With the help of RF expert Sterling Mann, the video delves into the physics of antennas, including polarization and field intensity. It promises a deeper dive into Maxwell's equations and practical demonstrations in a follow-up video, aiming to clarify the complex principles behind antenna function and electromagnetic wave propagation.

Takeaways

• 📡 Antennas are versatile devices used for transmitting and receiving various signals across a wide range of frequencies, from 100 kHz to 100 GHz.
• 🛠️ The satisfaction of making an antenna comes from applying a bit of math, cutting it to the right size, and seeing it work with a radio or Wi-Fi to extend range.
• 🔌 Antennas follow the same physical rules regardless of frequency, making the knowledge gained applicable across all bands.
• 💡 The video includes a physics demonstration using a light bulb and an antenna to examine electromagnetic fields, polarization, field intensity, and RF energy propagation.
• 🤝 Expert Sterling Mann, an amateur radio operator and RF engineer, is invited to provide insights and fill knowledge gaps on antenna operation.
• 🌐 Antennas are used in numerous applications, including music transmission, aircraft communication, GPS, satellite communications, cell phones, and IoT devices.
• 🌌 The physical size of an antenna is dictated by the frequency of operation, with lower frequencies requiring longer wavelengths and thus larger antennas.
• 🌳 Line of sight is crucial for radio frequency reception, with attenuation primarily caused by atmospheric conditions, precipitation, vegetation, or other obstructions.
• 📏 The dipole antenna, consisting of two radiating elements each a quarter wavelength long, is the simplest and a building block for more complex antennas.
• 🔄 Maxwell's equations, fundamental to understanding electromagnetic wave propagation, are briefly introduced, highlighting the relationship between electric and magnetic fields.
• 🌐 The antenna's function as a transducer converting electrical signals into electromagnetic waves is explained, emphasizing the concept of reciprocity for both transmission and reception.

Q & A

What is the main topic of the video?

The main topic of the video is antennas, discussing their importance, how they work, and their applications in various technologies.

Why are antennas fun to make according to Derek?

Antennas are fun to make because they give a sense of accomplishment through applying a bit of math, cutting the right size, and attaching a wire to a radio or Wi-Fi to extend range.

What is the significance of the electromagnetic field in the context of the video?

The electromagnetic field is significant as it is what the antenna manipulates to propagate radio frequency (RF) energy, which is demonstrated through a physics demonstration with a light bulb.

Who is Sterling Mann and what is his role in the video?

Sterling Mann is an amateur radio operator and an RF engineer who works in the field of antennas. He is invited to provide expert insights and fill in knowledge gaps in the discussion about antennas.

What is the relationship between frequency and wavelength as it pertains to antenna size?

The relationship is inversely proportional; as frequency increases, the wavelength decreases, and vice versa. This affects the physical size of the antenna, with higher frequencies requiring smaller antennas.

What is the concept of 'line of sight' in the context of radio frequency communication?

'Line of sight' refers to the clear path from one antenna to another for radio frequency communication, where attenuation typically comes from atmospheric conditions, not physical obstacles.

How does the video explain the propagation of radio signals using the ionosphere?

The video explains that at high frequencies (HF), radio signals can bounce off the ionosphere and the Earth to communicate around the globe, taking advantage of longer wavelengths that are less susceptible to attenuation.

What is a dipole antenna and how does it function?

A dipole antenna is composed of two radiating elements, each one quarter of a wavelength in length, separated by a short distance at the center. It functions by transforming an oscillating electrical signal into an electromagnetic wave that can propagate through space.

What are Maxwell's equations and why are they important for understanding antenna operation?

Maxwell's equations are a set of four fundamental equations in electromagnetism that describe how electric and magnetic fields interact. They are important for understanding how electromagnetic waves propagate through space, which is the principle behind antenna operation.

What is the difference between the near field and far field of an antenna?

The near field of an antenna is the region within about two wavelengths of the antenna, where the synthesis of the electromagnetic wave occurs. The far field is the region beyond the near field, where the electromagnetic wave has fully propagated and behaves as a transverse wave.

What is the purpose of the physics demonstration with the light bulb in the video?

The purpose of the physics demonstration with the light bulb is to visually examine the electromagnetic field and demonstrate the principles of polarization, field intensity, and RF energy propagation.

Outlines

00:00

📡 Introduction to Antennas and Their Importance

The video script begins with an introduction to the topic of antennas by Derek, the host of 'DC to Daylight.' He expresses his enthusiasm for the subject, highlighting the satisfaction derived from constructing antennas and understanding their underlying physics. The script explains that antennas are essential for transmitting and receiving signals across a wide range of frequencies, from 100 kHz to 100 GHz. The host also mentions an upcoming physics demonstration using a light bulb and an antenna to visualize electromagnetic fields. Sterling Mann, an amateur radio operator and RF engineer, is introduced as an expert who will contribute to the discussion. The video promises to cover various aspects of antenna theory, including polarization, field intensity, and propagation of radio frequency (RF) energy. A link to the full discussion between Derek and Sterling is provided in the video description.

05:00

🌐 The Physics of Antennas and Electromagnetic Waves

This paragraph delves into the physics of antennas, focusing on the relationship between frequency, wavelength, and antenna size. It explains that the size of an antenna is typically a fraction of the wavelength of the signal it's designed to transmit or receive. The script discusses the concept of line of sight communication, which applies to various frequency bands, and mentions the impact of environmental factors on signal attenuation. The paragraph also touches on the historical development of antenna technology, from early longwave antennas to modern compact designs that can be integrated into circuit boards. The host acknowledges the complexity of the subject and the need for Sterling Mann's expertise, particularly in understanding the transformation of electrical signals into electromagnetic waves and the role of Maxwell's equations in this process.

10:00

🔌 The Interface Between Transmission Lines and Antennas

In this section, the script discusses the interface between transmission lines and antennas, exploring how the movement of electrons in the transmission line influences the antenna's electromagnetic field. Sterling Mann provides clarification on this 'black magic' aspect of antenna operation, explaining that the acceleration of charges in the transmission line generates the electromagnetic fields necessary for RF propagation. The paragraph introduces the concept of Maxwell's equations, which are fundamental to understanding the behavior of electromagnetic waves. It also touches on the near field and far field regions of an antenna, explaining that within about two wavelengths of the antenna, the synthesis of the electromagnetic wave occurs, where both electric and magnetic fields are significant. The script concludes with a teaser for the next part of the video, which will include a demonstration of RF polarization and signal attenuation, as well as further discussions with Sterling Mann.

Keywords

💡Antenna

An antenna is a device used to transmit or receive radio frequency (RF) signals. In the video, it is described as a transducer that converts electrical signals into electromagnetic waves and vice versa. The script explains how antennas are used in various applications, such as Wi-Fi, GPS, and amateur radio, and how their size and performance are related to the frequency of operation.

💡Electromagnetic Field

The electromagnetic field is a physical field produced by electrically charged objects. The script discusses how this field is generated by the antenna through the acceleration of charges, which is integral to the propagation of radio waves. The video aims to demonstrate the behavior of these fields in relation to the antenna.

💡Polarization

Polarization refers to the orientation of the electric field vector of an electromagnetic wave. The video script mentions examining polarization in the context of antenna performance, which affects how RF energy propagates and is received by an antenna.

💡Field Intensity

Field intensity is a measure of the strength of an electromagnetic field. The script discusses how field intensity is related to the propagation of RF energy from an antenna and how it changes with distance from the antenna.

💡Radio Frequency (RF)

Radio frequency, or RF, is a rate of oscillation in the range of frequencies used to transmit information via radio waves. The video script explains that RF signals are part of the electromagnetic spectrum and that antennas are designed to work with specific RF frequencies.

💡Wavelength

Wavelength is the physical distance between two corresponding points of a wave, such as the distance between two consecutive peaks of an electromagnetic wave. The script explains how the wavelength is inversely proportional to frequency and how it dictates the physical size of an antenna.

💡Line of Sight

Line of sight refers to the direct path between the transmitter and receiver, which is crucial for RF signal transmission without obstructions. The video script mentions that RF signals can be received via line of sight, which is affected by factors like atmospheric conditions and physical barriers.

💡Dipole

A dipole antenna is a simple type of antenna consisting of two conductive elements, typically one-half wavelength long each. The script describes the dipole as the building block of many other antennas and explains how it generates both electric and magnetic fields to propagate radio waves.

💡Reciprocity

Reciprocity in the context of antennas means that an antenna can perform equally well in both transmitting and receiving modes. The script mentions this principle and how it applies to the operation of antennas.

💡Maxwell's Equations

Maxwell's Equations are a set of four fundamental equations that describe how electric and magnetic fields are generated and altered by each other and by charges and currents. The script briefly introduces these equations as the foundation for understanding the propagation of electromagnetic waves, which is central to the operation of antennas.

💡Near Field and Far Field

The near field and far field refer to two regions around an antenna where the electromagnetic field behaves differently. The script explains that within about two wavelengths of the antenna, the fields are synthesizing to form an electromagnetic wave, which is part of the near field region.

Highlights

Derek discusses the enjoyment and sense of accomplishment from making antennas and their applications in various technologies.

The video covers the physics of antennas, including an electromagnetic field demonstration with a light bulb.

Introduction to Sterling Mann, an expert in RF and antenna field, who contributes to filling knowledge gaps.

Explanation of how the rules of physics apply to antenna design across a wide range of frequencies.

Discussion on the relationship between frequency, wavelength, and antenna size, with the formula for wavelength calculation.

The concept of line of sight for radio frequency reception and the factors affecting signal attenuation.

Insight into how technology has advanced to allow for the use of shorter wavelengths and smaller antenna sizes.

The advantage of lower frequencies for long-range communication due to less susceptibility to attenuation.

Introduction to the dipole antenna, its composition, and function as a basic building block for other antennas.

Clarification on the generation of electromagnetic waves by oscillating electrical signals in antennas.

Importance of Maxwell's equations in understanding the propagation of electromagnetic waves.

Explanation of the relationship between electric and magnetic fields as per Maxwell's equations.

Sterling Mann provides expert clarification on the transmission of RF signals and the role of accelerated charges.

Discussion on the near field and far field of an antenna and their significance in electromagnetic wave synthesis.

Introduction to the second part of the video, which includes a demonstration on RF polarization and signal tapering.

Promise of further exploration of antenna modeling and software in the continuation of the video series.

Invitation for audience interaction and a tease for the next video in the series.

Transcripts

welcome back to DC to Daylight my name

is Derek and in this video I obviously

want to talk about antennas so antennas

are one of those things they're really

fun to make and it gives you the sense

of accomplishment just throwing a little

bit of math at this thing and just

cutting it to the right size and

attaching a wire to a radio maybe your

Wi-Fi to extend your range or something

like that it's easy to do and the rules

of physics apply for 100 kilohertz all

the way up to you know 100 gigahertz so

you're not limited to any particular

band anything you learn here today will

be relevant for all of those frequencies

now we're also going to do an

interesting physics demonstration with

this little light bulb in this antenna

here and we're going to kind of examine

what the electromagnetic field is

actually doing okay so we'll look at

polarization we'll look at the field

intensity and where this kind of antenna

actually propagates that RF energy now

where I'm lacking in knowledge I've

asked an expert to come in and fill in

the gaps that is Sterling Mann he's an

amateur radio operator like myself he

actually works in the field of RF on

antennas so I've asked him to come on

and kind of explain a little bit about

that so I'm conversation went on for

quite a bit so I've cut this up and put

relevant parts of that discussion in

here a link to the full discussion

between he and I are down in the

description so you can check it out

there all right so enough jibber jabber

let's get right into antennas

[Music]

foreign

s are all around us we use them to

transmit and receive things like music

communicate with aircraft they're used

in guidance systems GPS satellite comms

cell phones and iot devices to name a

few applications those applications all

operate on specific frequencies within

the RF spectrum and that frequency

dictates the physical size of the

antenna and its propagation

characteristics the lower the frequency

the longer the wavelength and the higher

the frequency the shorter the wavelength

in general any radio frequency can be

received via what is called the line of

sight this goes for vlf hfvhf UHF so on

and so forth that means there's a clear

path from one antenna to the other and

the only attenuation in that pathway

typically comes from moisture in the

atmosphere precipitation vegetation or

overzealous squirrels storing nuts for

winter

we're all familiar with typical Wi-Fi

performance at 2.4 gigahertz this is a

fairly short wavelength so antennas can

usually be fitted to a circuit board

Trace internal to the device however

you've probably noted that the range is

severely limited and items around the

house can block your signal now old

school Electronics usually use a lower

frequency requiring ridiculously long

antenna from back in the 1920s 30s and

40s the shortwave and am bands were

considered high frequency

and as technology advanced we came to

understand how to design and integrate

systems utilizing shorter and shorter

wavelengths and as a result antennas

became smaller all that being said when

it comes to long-range Communications

lower frequencies still win out longer

wavelengths right as they aren't as

susceptible to attenuation as UHF and

microwave signals in fact it's very

common at HF 3 to 30 megahertz to take

advantage of bouncing radio signals off

the ionosphere and the Earth itself in

order to communicate around the globe

[Music]

so I want to thank Sterling Mann call

sign n0 SSC for coming on the channel

and helping us understand and fill in

the gaps about uh what I can't explain

intelligently

um so uh Sterling you are a ham radio

operator you've got your own YouTube

channel you've got a Blog and zero SSC I

think it's.com is that correct yeah

that's right okay and you are an uh an

actual RF engineer correct yeah I try

proof I'm a ham here's my qsl card with

the vla uh picture

um I think Paul Hardin na5n he's an

engineer Who develops the receivers at

the radio Observatory the very large

array in New Mexico famous from contact

and stuff and I had the opportunity to

work there work with him and learn a lot

and now you know that led me into a

career in

um the defense industry which is where

basically all of the cool RF stuff is so

I'm gonna I'm gonna from my perspective

you're an expert and uh hopefully you

can fill in these gaps

[Music]

so what is an antenna in the case of a

transmitting antenna it's a kind of

transducer that can transform an

oscillating electrical signal into an

electromagnetic wave which can propagate

through space this same antenna can

usually be used as a receiver as well

this is called reciprocity many of the

topics we'll cover will apply to both

receive and transmit applications though

there are some subtle differences we'll

touch on later an important concept to

understand before we get into this is

the wavelength and frequency

relationship as it pertains to antenna

physical size so in a vacuum our RF

signal travels at the speed of light

denoted as C and the antenna's size is

usually some fractional value of

wavelength of the signal we're operating

on wavelength is defined as Lambda is

equal to the velocity of propagation C

divided by the frequency in hertz note

that this is the theoretical wavelength

in a vacuum using the speed of light as

a constant light and radio waves are

both electromagnetic radiation after all

in the next video we'll show why this

theoretical value doesn't exactly match

up in the real world and we'll have to

tweak our antenna a little bit we can

also find the frequency from the

wavelength so we algebraically switch

things up and we find that frequency is

equal to C divided by the wavelength and

of course if we were hanging out in a

vacuum chamber we could prove that the

speed of light is as currently defined

as 299 million 792 458 meters per second

using the formula C is equal to the

frequency times the wavelength that's

not a task I'm personally interested in

so what does all of this tell us as the

frequency goes up the wavelength

decreases and as the antenna's physical

size is directly linked to the

wavelength as we said our antenna size

requirement gets smaller as well the

simplest of all antennas and the

building block of many other antennas is

the dipole it's composed of two

radiating elements both one quarter

wavelength in length separated by a

short distance at the center the overall

length being one-half Lambda or one-half

the wavelength from a transmitting

perspective we would connect one side of

our signal source to one element and the

other side to the second element when we

drive this antenna with a specific AC

signal it transfer forms this

oscillation into both an alternating

electric field and 90 degree orthogonal

magnetic field these fields exist

together and allow the radio wave to

travel through space to be intercepted

by a receiving antenna so

hi

future me here so I was just about to

turn my video in and I thought I was

done talking about everything but I

realized that I didn't really set the

groundwork for Maxwell's equations which

are integral integral to understanding

how electromagnetic waves propagate

through space okay so Sterling and I

talk about these things and we're

throwing terms around but I don't really

explain what it is so let's just go

through a few of the rules of Maxwell's

equations on the computer over here the

first equation we'll look at relates to

the magnetic field it reads the

Divergence of a magnetic field is equal

to zero so what does that mean the funny

looking triangle called the nabla and

also the dot represents the magnetic

field lines that flow through a closed

volume of space the B term represents

the magnetic field Direction and

intensity overly simplify this formula

means if we take a chunk of space and a

certain amount of flux enters that

volume the same amount exits that volume

the difference between the two is zero

this is important as it shows all

magnetic fields are dipoles in nature

they have a north and a South Pole and

the lines of force must complete a

circuit the second formula deals with

the electric field component it says the

Divergence of the electric field e is

equal to rho divided by Epsilon 0. rho

is the charge density so how many

electrons are piled together or not

piled together in our space in this case

an electric field begins at a positive

charge and ends at a negative charge now

let's take a finite enclosed volume and

place a charge inside of that container

we can see that with a positive charge

there are more field lines exiting than

entering in the case of a negative

charge there are more field lines

entering than exiting so in this example

the electric field is non-zero or rho

divided by Epsilon zero we recall that

rho is the charge density in epsilon 0

is a constant known as the permittivity

of free space it tells us how electric

Fields behave in a dielectric the third

formula is a bit more complicated it

says that the curl the right triangle X

bit of the electric field is equal to

the rate of change of the magnetic field

so this one tells us that the electric

field can't exist without a magnetic

field and also depends on a fluctuating

B component that's as far as I'd like to

go with this one but the important point

is an electric field can't exist without

a magnetic field and vice versa now this

last equation says the curl of the

magnetic field depends on a changing

electric field note the MU zero which is

the permeability of free space think of

it like the permittivity but for

magnetics it's also a constant and we've

also got a new term J which represents

current flow also called the

displacement current the right hand rule

applies here so this formula tells us

which direction the lines of force are

flowing in relation to the current all

right so now that we've gotten that out

of the way let's get on with it without

going beyond the scope of this video

we'll trust in Maxwell and say that our

magnetic field cannot exist without an

electric field these two fields are both

orthogonal or 90 degrees to each other

as they propagate through space can I

already say that I already said that so

now we know we have an e field and a b

field that can travel through space and

we know we have an alternating current

and voltage on our antenna that generate

those fields how does that actually

occur I was a little fuzzy on this so

was one of my things that I wanted

Sterling to clarify so let's see what he

has to say about this uh what I wanted

some clarification on this is kind of

the black magic side of things from my

perspective is what happens at the

transmission line antenna interface and

how does uh I guess we're just wiggling

electrons back and forth how does that

translate to propagating RF

so that the the real answer to that

question is obviously the wave equation

the the and it's obfuscated by like the

whole Maxwell's equations thing and and

I am I know what they are but I'm not at

the point where I want to tattoo them on

my body and say like yeah this is the

Empire's law this is you know fairy's

law but

um in a nutshell that's what's happening

is the electrons are wiggling the

charges are wiggling they're being

accelerated the key word there is an

accelerated charge

um through the transmission line and

even through the transmission line it

gets to antenna so say we're looking at

a dipole where you have you know your

you know balance wire transmission line

and then it goes to two equally you know

equal length pieces of wire it goes up

there and it starts influencing the

charge on that piece of wire that's the

key is a charge an electron or whatever

is accelerating back and forth and

because of the um wave equation which is

derived from faradays and Amber's law

um and and it's really hard to say it's

really kind of Mis unintuitive to say

because of an equation that we come up

um but you know maybe the better term is

because of the natural laws of the

universe when you move a charge it

propagates its field so a charge has a

field and if you accelerate a charge it

you know the field moves with it and if

you move it back and forth that field

kind of reverberates there's some really

good diagrams out there that kind of

show the intuitive kind of look but it's

basically the same I think of an

antennas as a loudspeaker for instead of

Air instead of you know a speaker moving

air and you know changing pressure in

air essentially a very similar thing is

going on but instead of air it's

electrons being able to sense or know in

in kind of an anthropomorphized way what

the other electrons are doing and then

continually you know propagating out

into Infinity

um so at the interface ampere's law I

think people in electronics are familiar

with that right hand rule right we send

a charge going a certain direction and

we wrap our hand around it and the flux

lines go this Direction that's primarily

the magnetic component right

what is what tells us what the I guess

electric field component because the

propagating RF signal is an EM wave

right has a magnetic component and an

electric field component so what what is

that

so that also stems from you know

Maxwell's equations and and I kind of

want to use the the near field far field

idea of an antenna to kind of decompose

where the fields are actually coming

from so when you're really close to an

antenna my hand's the antenna

um and if you're really close means

within about two wavelengths so you take

your frequency that has a certain

wavelength based on the speed of light

so let's call 100 megahertz has a

wavelength of about three meters so if

you're within six meters of a antenna

that works at 100 megahertz that's the

near field area what's happening there

in that in that region is the synthesis

if you will of the electromagnetic wave

so both the electric field and the

magnetic field well unfortunately this

video turned out to be much longer than

I had originally planned and there's a

lot of information to cover so we had to

split it up into two different parts we

did get a chance to give a very cursory

overview of Maxwell's equations and

provide some idea of the code existence

of electromagnetic and electric fields

and kind of how they work together to

propagate RF through space now in part

two of this topic we'll do a

demonstration on the bench which

demonstrates the RF polarization and how

a signal tapers off the further we move

away from the source okay we'll also do

a little bit of antenna modeling and

software and of course we'll hear some

more from our special guest Sterling

Mann anyway you can get a hold of me

down in the comments and as always you

can interact directly with the element

14 team including myself by clicking the

link down in the description that's all

for me we'll see you next time and have

a good one

[Music]

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