Antennas Part I: Exploring the Fundamentals of Antennas - DC To Daylight
Summary
TLDRIn '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
📡 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.
🌐 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.
🔌 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.
Mindmap
Keywords
💡Antenna
💡Electromagnetic Field
💡Polarization
💡Field Intensity
💡Radio Frequency (RF)
💡Wavelength
💡Line of Sight
💡Dipole
💡Reciprocity
💡Maxwell's Equations
💡Near Field and Far Field
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]
foreign
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