KB6NU's Ham Radio Blog

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2016 Extra Class Study Guide: E3C - radio horizon, propagation prediction

Posted: 09 Mar 2016 12:09 PM PST
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E3C Radio-path horizon; less common propagation modes; propagation
prediction techniques and modeling; space weather parameters and amateur
radio

While we say that VHF/UHF communication is “line of sight,� the distance
that a VHF/UHF radio wave will travel is slightly longer than the
line-of-sight distance. We call this distance the “radio horizon� or
“radio-path horizon.� The VHF/UHF radio-path horizon distance exceeds the
geometric horizon by approximately 15% of the distance. (E3C06) The
radio-path horizon distance exceeds the geometric horizon because of
downward bending due to density variations in the atmosphere. (E3C14)

Amateur radio operators may sometimes use ground-wave propagation to
communicate. One important thing to know about this type of propagation is
that the maximum distance of ground-wave propagation decreases when the
signal frequency is increased. (E3C12) Vertical polarization is the best
type of polarization for ground-wave propagation. (E3C13) So, if you really
want to make a contact via ground wave, use a vertical antenna on the 160m
band.

Prediction techniques and modeling

Since its very advantageous to know the propagation conditions for a
particular signal path, many hams use propagation prediction software to
choose what frequency bands to use. One of these software packages is
called VOACAP, because it was developed by engineers at the Voice of
America (VOA). VOACAP software models HF propagation. (E3C11)

Often, these types of software packages use a technique called ray tracing.
In regard to radio communications, the term ray tracing describes the
process of modeling a radio waves path through the ionosphere. (E3C01)

Propagation prediction software uses data such as the A index and K index
to model propagation. Both of these provide a measure of geomagnetic
activity, which affects HF propagation. A rising A or K index indicates
increasing disruption of the geomagnetic field. (E3C02) A high A-index or
K-index usually means that HF propagation will be poor. Polar paths are
most likely to experience high levels of absorption when the A index or K
index is elevated. (E3C03)

The interplanetary magnetic field has a very strong affect on HF
propagation. The value of Bz (B sub Z) represents the direction and
strength of the interplanetary magnetic field. (E3C04) A southward
orientation of Bz (B sub z) increases the likelihood that incoming
particles from the Sun will cause disturbed conditions. (E3C05) HF
propagation is generally poor when Bz is oriented southward and geomagnetic
conditions are disturbed.

Space weather parameters and amateur radio

Because solar radiation creates the ionosphere, solar activity has a great
impact on radio wave propations. These conditions are often referred to as
space weather.

Solar flares, for example, emit an enormous amount of radiation. Depending
on how much radiation they emit, the effect on HF propagation can be good
or bad. If the Earth receives only enough radiation to increase ionization
in the upper layers of the ionosphere, HF propagation is improved.

If the level of radiation is higher, the lower levels of the ionosphere
could become more energized. When this happens, they absorb more RF energy,
and HF propagation is poor. A sudden rise in radio background noise
indicates that a solar flare has occurred. (E3C15)

Solar flares are categorized by intensity. Class A solar flares are the
least intense. Class X is the descriptor that indicates the greatest solar
flare intensity. (E3C07) In between Class A and Class X are Class B, Class
C, and Class M.

Within each class, solar flares are assigned a value from 1 – 9. The
intensity of an X3 flare is twice as great as that of an X2 flare. (E3C09)

The National Oceanic and Atmospheric Administration (NOAA) has developed
what they call Space Weather Scales to communicate to the general public
the current and future space weather conditions and their possible effects
on people and systems. The G scale indicates geomagnetic conditions. The
space weather term G5 means an extreme geomagnetic storm. (E3C08)

Sunspots are often used to predict HF propagation conditions. The more
sunspots, the better HF propagation is. Paramater 304a may, however, be an
even better indicator of radio conditions. The 304A solar parameter
measures UV emissions at 304 angstroms, correlated to solar flux index.
(E3C10) These UV emissions are one of the principle causes of F2 layer
ionization.

The post 2016 Extra Class Study Guide: E3C radio horizon, propagation
prediction appeared first on KB6NUs Ham Radio Blog.


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Amateur radio in the news: NPOTA, hams young and old, Skywarn

Posted: 09 Mar 2016 11:26 AM PST
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Lewis and Clark Historic Site welcomes ham radio operators.Â*To help
celebrate the National Park Service’s centennial, the Lewis and Clark State
Historic Site is welcoming amateur radio operators for a special event
March 19. Radio enthusiasts will demonstrate emergency and portable
communications while making contact with other stations across the United
States.Â*Radio operators are setting up National Parks on the Air stations
throughout 2016 at national parks, historic trails and battlefields.
Although it is a state of Illinois site, the Lewis and Clark site in
Hartford is the first stop on the Lewis and Clark National Historic Trail.

Teen aces two ham radio exams in FDL.Â*Isaac Lundberg, 13 years old, a
seventh grade student at Redeemer Lutheran School in Fond du Lac,Â*joined
other applicantsÂ*at a test session sponsored by theÂ*Fond du Lac Amateur
Radio Club recently. He first took the Technician Class license exam, aced
it, and then shocked everyone and proceeded to aceÂ*the General Class
Exam.Â*When you are only 13 years old, its an incredible accomplishment!

From World War II until today, University Heights Goldfarb and his radios
have been inseparable. Jack Goldfarb is whats known as an amateur radio
operator.Â*Goldfarb, of University Heights, has been talking on his ham
radio since he was 16. It was at that age he studied to pass the test given
for one to obtain an amateur radio license.Â*And, when did he get that
license?Â*I got my license in April, 1941, Goldfarb replied. I went downtown
(Cleveland) to the FCC office that was in the old post office building. I
still remember Mr. Russ was the FCC radio inspector there.

Decherd feels sense of adventure, helping others as a storm spotter.Â*When a
tornado hit the ground near the Quad-Cities just two days before Christmas
2015, most people were waiting it out in their basement. Not so National
Weather Service SKYWARN storm spotter volunteer Doug Decherd, who with
others, was hard at work tracking the storm.

The post Amateur radio in the news: NPOTA, hams young and old, Skywarn
appeared first on KB6NUs Ham Radio Blog.