Sporadic E Propagation

00:13:44
https://www.youtube.com/watch?v=Yp8QV4F3yA8

Sintesi

TLDRThis video explores the different layers of Earth's atmosphere, specifically the ionosphere, which plays a crucial role in radio communication. Focus is given to the E layer, situated between 100 and 120 kilometers above Earth. This layer contains ionized clouds capable of reflecting VHF radio signals that would otherwise exit into space. Amateur radio operators particularly benefit from the E layer's capability to enhance radio signal propagation, including a phenomenon called sporadic E, where highly ionized patches occasionally form, facilitating long-distance communication. These e-clouds allow for multiple signal hops, potentially expanding communication range up to 5000 kilometers or more, especially over water. The video's detailed analysis delves into sporadic E formation, associated with factors like wind shear, geomagnetic activity, and possibly thunderstorms. While the exact causes remain under study, these patches can significantly enhance or degrade signal quality, influencing both VHF and UHF wave propagation. Overall, the video underscores the complex yet fascinating interactions within the ionosphere and their impacts on radio signal paths, honing in on the challenges and benefits for radio communication enthusiasts.

Punti di forza

  • 🌌 Earth's atmosphere consists of five layers: troposphere, stratosphere, mesosphere, thermosphere, and exosphere.
  • 📡 The ionosphere is crucial for radio signal propagation, comprising D, E, and F regions.
  • 🔄 E-layer ionization reflects VHF signals, enhancing communication for radio operators.
  • 🌪️ Sporadic e-clouds in the E layer unpredictably enhance radio signal reach.
  • 🛰️ Amateur radio operators exploit ionospheric conditions for global communication.
  • ☀️ Solar activity significantly affects the ionization levels in the ionosphere.
  • 💡 The phenomenon of maximum usable frequency (MUF) is key in radio signal reflection.
  • 🌐 Multiple ionized patches facilitate double-hop communication paths over vast distances.
  • ⛈️ E-cloud formation theories include links to meteor showers and thunderstorms.
  • ⚡ Intense electrical activity can coincide with sporadic e-cloud formation, aiding signal paths.

Linea temporale

  • 00:00:00 - 00:05:00

    The video begins by exploring the various layers of Earth's atmosphere, highlighting the E-layer in the ionosphere that reflects VHF radio signals back to Earth and is important for amateur radio operators. Earth's atmosphere comprises layers such as the troposphere, stratosphere, mesosphere, thermosphere, and exosphere. The ionosphere has regions like the D, E, and F layers that vary in their ability to reflect radio waves, with the E-layer housing ionized clouds that sporadically form and significantly interest amateur radio enthusiasts.

  • 00:05:00 - 00:13:44

    The concept of sporadic E is presented, detailing how highly ionized patches in the E-layer, also known as sporadic E-clouds, significantly impact radio signal propagation. The formation of these clouds, although unpredictable, appears related to factors such as wind shear, thunderstorms, and meteor activity. The critical frequency above which signals are not refracted back to Earth is termed the maximum usable frequency (MUF). Sporadic E propagation can cause signals to travel beyond normal distances, facilitating long-range communication, but this phenomenon remains complex and not fully understood.

Mappa mentale

Mind Map

Domande frequenti

  • What is the E layer of the ionosphere?

    The E layer is a part of the ionosphere, located between 100 and 120 kilometers above Earth's surface, capable of reflecting VHF radio signals back to Earth.

  • Why is the ionosphere important for radio operators?

    The ionosphere can reflect radio signals back to Earth, enabling long-distance communication, which is crucial for amateur radio operators.

  • What are sporadic e-clouds?

    Sporadic e-clouds are highly ionized patches in the E layer of the ionosphere that occasionally reflect radio signals.

  • How do sporadic e-clouds affect VHF radio signals?

    Sporadic e-clouds enhance VHF radio signal propagation, allowing for longer signal paths and increased range.

  • How do factors like thunderstorms and wind shear affect the E layer?

    These factors can influence the formation of sporadic e-clouds by causing ion concentration and compression.

  • What causes sporadic E events?

    The exact cause is unknown, but theories suggest connections to wind shear, thunderstorms, and meteor debris.

  • What is the maximum usable frequency (MUF) in radio terminology?

    MUF is the highest frequency that can be reflected off the ionosphere back to Earth.

  • Which atmospheric layer experiences variations due to solar activity?

    The D region of the ionosphere experiences significant changes due to intense solar activity.

  • How do radio propagation conditions change with altitude in the ionosphere?

    The ionization levels and thus radio wave propagation characteristics change with altitude across different layers of the ionosphere.

  • What are the main layers of the ionosphere mentioned?

    The main layers mentioned are the D, E, and F regions, each with unique properties and effects on radio signals.

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Scorrimento automatico:
  • 00:00:02
    [Music]
  • 00:00:15
    the view from the edge of the exosphere
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    480 kilometers above the surface of our
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    planet
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    is awe-inspiring
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    380 kilometers below lies the e
  • 00:00:29
    layer a 20 kilometer wide radio
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    reflective ionospheric layer
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    between 100 and 120 kilometers
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    above the surface of our planet
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    the ionization of this layer is
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    fascinating
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    as well as challenging for amateur radio
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    operators around the world
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    this is the layer where ionized e-clouds
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    live
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    [Music]
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    e-clouds reflect vhf radio signals that
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    would otherwise escape the earth's
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    atmosphere
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    back to earth
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    our atmosphere has five layers
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    the lowest layer is the troposphere
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    which is where aircraft fly
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    and where nearly all of our weather
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    occurs
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    the stratosphere is next with the
  • 00:01:29
    mesosphere
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    and the thermosphere above that
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    sitting above all these layers is the
  • 00:01:36
    exosphere
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    a place for spacecraft and satellites
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    [Music]
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    earth's atmosphere contains a series of
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    regions that have a relatively large
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    number
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    of electrically charged atoms and
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    molecules
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    as a group these regions are
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    collectively called
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    the ionosphere
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    there are three main regions of the
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    ionosphere
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    the d layer around 75 kilometers up
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    the e layer 110 kilometers up
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    and the f layer that starts at about 150
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    kilometers
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    and extends upwards sometimes as high as
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    500 kilometers
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    [Music]
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    these regions do not have sharp
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    boundaries and the altitudes at which
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    they occur
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    vary during the course of the day and
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    from season to season
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    [Music]
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    amateur radio operators take a keen
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    interest in the tropospheric region of
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    the atmosphere
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    as well as the e-layer as these two
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    regions can propagate vhf radio signals
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    well beyond that of line of sight
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    [Music]
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    the troposphere is the lowest part of
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    our atmosphere
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    and what takes place within its
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    boundaries largely determines our
  • 00:02:56
    weather
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    [Music]
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    its upper boundary is the temperature
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    inversion layer
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    known as the tropopause which lies
  • 00:03:04
    between 8 kilometers
  • 00:03:05
    and 16 kilometers high depending on the
  • 00:03:08
    latitude
  • 00:03:09
    and prevailing conditions
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    the low level of ionization is
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    negligible as far as radio waves are
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    concerned
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    however small variations in the physical
  • 00:03:21
    properties of the air
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    give rise to variations in the
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    refractive index
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    which results in several distinct
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    tropospheric propagation modes
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    more about this in another video
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    the d region lies between 60 and 90
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    kilometers above the earth's surface
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    it absorbs radio waves particularly at
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    hf
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    because the electrons are frequently
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    colliding and dissipating the energy of
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    the waves
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    instead of propagating them
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    [Music]
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    although the d region is almost
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    transparent at vhf and uhf
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    it does contribute to ionospheric
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    forward scatter
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    especially when intense solar activity
  • 00:04:04
    produces an excess of ultraviolet
  • 00:04:06
    and high energy x-rays which can
  • 00:04:08
    penetrate
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    to this depth of the atmosphere
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    the e region is defined as that between
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    90
  • 00:04:17
    and 120 kilometers above the earth's
  • 00:04:20
    surface
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    and it can be regarded as the transition
  • 00:04:23
    zone from the earth's atmosphere
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    into space
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    there are discontinuities in pressure
  • 00:04:30
    temperature
  • 00:04:31
    and chemical composition at this height
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    above 90 kilometers ions predominate
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    over neutral atoms
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    most of the shortwave ultraviolet rays
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    and
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    less energetic x-rays from the sun are
  • 00:04:47
    absorbed by ionizing the e-layer
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    although the ionization is normally
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    insufficient to reflect vhf radio waves
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    back to earth
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    some thin and dense layers of ionization
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    occasionally occur
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    known as sporadic e
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    this is also the region where auroras
  • 00:05:07
    and meteors produce ionization
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    capable of reflecting vhf and uhf
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    signals
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    above the e region lies the f region
  • 00:05:19
    which in daytime usually subdivides into
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    two distinct layers
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    f1 and f2
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    the lower f1 layer plays little part in
  • 00:05:29
    vhf propagation
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    except to contribute some refraction if
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    vhf radio waves are returned back
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    towards the earth
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    it's from the f2 layer heights
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    the f2 layer has an average effective
  • 00:05:43
    height
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    of between 300 and 350 kilometers
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    which can increase to between 450 and
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    kilometers the layer varies between 100
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    and 200 kilometers deep during the peak
  • 00:05:58
    of solar activity
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    the f2 layer can provide worldwide
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    contacts on the six meter band
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    however the f2 layer does not reach the
  • 00:06:07
    levels of ionization required to return
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    higher frequency
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    vhf and uhf signals to the earth except
  • 00:06:14
    in the special case
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    of trans equatorial propagation
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    returning to the e-layer sporadic e is
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    probably the most interesting and
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    exciting form of signal enhancement for
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    the amateur radio operator
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    highly ionized patches or clouds
  • 00:06:34
    occasionally form in the e region of the
  • 00:06:37
    ionosphere
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    known as sporadic e clouds they're
  • 00:06:40
    usually fairly small in size
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    but larger clouds or multiple clouds
  • 00:06:45
    often form during substantial openings
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    as the name indicates sporadically is
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    not easy to predict
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    after almost 80 years of study the true
  • 00:06:57
    cause of sporadica
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    is still unknown there are many
  • 00:07:00
    different theories as to
  • 00:07:02
    how and why sporadic e-clouds form
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    there seems to be no correlation between
  • 00:07:08
    the ionization level
  • 00:07:10
    or formation of sporadic e-clouds and
  • 00:07:13
    the 11-year sunspot cycle
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    but there is evidence to suggest that
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    the primary cause of spreader key cloud
  • 00:07:19
    formation
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    is wind shear a purely weather related
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    phenomenon
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    intense high altitude winds traveling in
  • 00:07:28
    opposite directions at different
  • 00:07:30
    altitudes
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    produce wind shear it's believed that
  • 00:07:34
    these wind shears
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    in the presence of the earth's
  • 00:07:37
    geomagnetic field
  • 00:07:39
    cause ions to be collected and
  • 00:07:40
    compressed into thin
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    iron-rich layers approximately one
  • 00:07:45
    to one and a half kilometers in
  • 00:07:47
    thickness
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    the area of these patches can vary from
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    a few meters
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    to hundreds or even thousands of square
  • 00:07:56
    kilometers
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    along the same line is the theory that
  • 00:08:02
    sporadic e-clouds are formed in the
  • 00:08:05
    vicinity of thunderstorms
  • 00:08:06
    by the intense electrical activity
  • 00:08:08
    associated with them
  • 00:08:12
    there is often but not always a
  • 00:08:14
    correlation between thunderstorm
  • 00:08:15
    activity
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    and the formation of sporadic e clouds
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    enough to make the theory
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    very feasible however strong
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    thunderstorms often form along frontal
  • 00:08:26
    boundaries an intense wind shear is
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    usually found along the same frontal
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    boundaries that produce these
  • 00:08:31
    thunderstorms
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    likewise strong sporadic e activity
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    often appears
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    when there is no apparent thunderstorm
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    activity along or near the propagation
  • 00:08:41
    path
  • 00:08:44
    yet another emerging theory suggests
  • 00:08:46
    that sporadic e-clouds are formed by
  • 00:08:48
    concentrations of meteor debris
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    again there seems to be a strong
  • 00:08:53
    correlation between meteor shower
  • 00:08:54
    activity
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    and the number and intensity of sporadic
  • 00:08:58
    e-clouds
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    it's all speculation though as nobody
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    has presented a definitive explanation
  • 00:09:06
    for how and why sporadic e-clouds form
  • 00:09:10
    [Music]
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    the amount by which the path of a radio
  • 00:09:15
    signal is refracted by sporadic e-clouds
  • 00:09:18
    depends on the intensity of ionization
  • 00:09:20
    and the frequency
  • 00:09:22
    of the signal for a given level of
  • 00:09:25
    ionization
  • 00:09:26
    the signal refraction angle will
  • 00:09:28
    decrease as the frequency is increased
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    above a certain critical frequency
  • 00:09:34
    refraction of the signal will be
  • 00:09:36
    insufficient to return it to the surface
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    of the earth
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    this critical frequency is known as the
  • 00:09:42
    maximum usable frequency
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    or muf
  • 00:09:47
    sporadic e is very common on the low vhf
  • 00:09:50
    frequencies during the summer months
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    it's not uncommon for the muf to rise up
  • 00:09:56
    to
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    and stop at a particular frequency
  • 00:09:58
    within the fm broadcast band
  • 00:10:01
    distant signals will be heard below the
  • 00:10:03
    muf while only local
  • 00:10:06
    or tropospherically enhanced signals
  • 00:10:08
    will be heard above the muf
  • 00:10:12
    over the years it's been observed that
  • 00:10:14
    the signal strength of the received
  • 00:10:16
    spreader key signals
  • 00:10:17
    will be greatest just below the maximum
  • 00:10:20
    usable frequency
  • 00:10:23
    since the bending angle or angle of
  • 00:10:25
    refraction decreases as the signal
  • 00:10:27
    frequency is increased for a given
  • 00:10:29
    ionization level
  • 00:10:31
    we can surmise that the most distant
  • 00:10:33
    receptions will occur
  • 00:10:34
    as we approach the maximum usable
  • 00:10:36
    frequency
  • 00:10:38
    in other words an e-cloud will support
  • 00:10:40
    longer signal paths at 100 megahertz
  • 00:10:43
    than it will
  • 00:10:44
    at 50 megahertz
  • 00:10:47
    in this example ecloud 1 is more
  • 00:10:50
    intensely ionized
  • 00:10:51
    and thus capable of refracting signals
  • 00:10:53
    at a sharper angle
  • 00:10:55
    producing a shorter skip distance for a
  • 00:10:57
    given frequency
  • 00:11:00
    signals being refracted by ecloud number
  • 00:11:02
    two are returned to earth at a lesser
  • 00:11:04
    angle
  • 00:11:05
    thus producing longer skip distances
  • 00:11:09
    with clouds two and three in alignment
  • 00:11:11
    along a signal path
  • 00:11:12
    double hop skip can occur
  • 00:11:16
    with this cloud alignment signals from
  • 00:11:18
    both the transmitter and the signal hop
  • 00:11:20
    zone
  • 00:11:21
    would be heard at the receiving station
  • 00:11:24
    the maximum distance for a single hop
  • 00:11:27
    sporadically propagated signal
  • 00:11:29
    is about two and a half thousand
  • 00:11:30
    kilometers
  • 00:11:32
    however if multiple sufficiently ionized
  • 00:11:35
    patches exist
  • 00:11:36
    in a line along a particular signal path
  • 00:11:39
    this can extend the range of e-layer
  • 00:11:41
    propagation signals
  • 00:11:42
    out to around 5000 kilometers and beyond
  • 00:11:46
    [Music]
  • 00:11:47
    if the midpoint of a double hop happens
  • 00:11:50
    to be on the water
  • 00:11:51
    such as the ocean the signals will be
  • 00:11:53
    stronger
  • 00:11:54
    and there's less likely to be
  • 00:11:55
    interference from midpoint stations
  • 00:11:59
    sometimes we hear sporadic e-stations
  • 00:12:02
    that don't seem to fit the normal model
  • 00:12:04
    in terms of path distance
  • 00:12:07
    it's not uncommon to receive signals
  • 00:12:08
    beyond the range of what would be
  • 00:12:10
    considered
  • 00:12:11
    normal for a single hog but less than
  • 00:12:13
    the range expected for a normal double
  • 00:12:16
    hop
  • 00:12:18
    there have been many theories to try and
  • 00:12:20
    explain this phenomenon
  • 00:12:21
    including paths along multiple sporadic
  • 00:12:24
    e-clouds
  • 00:12:26
    in this example neither e-cloud is
  • 00:12:29
    sufficiently ionized to return a single
  • 00:12:31
    hop to earth
  • 00:12:32
    with two weak clouds working together
  • 00:12:35
    the refraction
  • 00:12:36
    angles of both es clouds are essentially
  • 00:12:38
    added
  • 00:12:40
    this would have the effect of raising
  • 00:12:42
    the apparent maximum usable frequency
  • 00:12:44
    and ultimately returning the signal to
  • 00:12:46
    earth at a greater than normal
  • 00:12:48
    e distance
  • 00:12:52
    this would account for the variable path
  • 00:12:54
    distances which fall between that of
  • 00:12:56
    single and double hop sporadic e
  • 00:12:58
    path distances although sporadic e may
  • 00:13:02
    appear to give an improvement in some hf
  • 00:13:04
    communications
  • 00:13:05
    it can also have the effect of degrading
  • 00:13:07
    some hf
  • 00:13:08
    signals however the intermittent nature
  • 00:13:12
    of the sporadically clouds
  • 00:13:13
    and the fact that the clouds are very
  • 00:13:15
    mobile means that any effects
  • 00:13:17
    are likely to be relatively short-lived
  • 00:13:34
    [Music]
  • 00:13:44
    you
Tag
  • ionosphere
  • radio signals
  • E layer
  • sporadic e-clouds
  • VHF propagation
  • amateur radio
  • MUF
  • wave propagation
  • atmospheric layers
  • auroras