KB6NU's Ham Radio Blog

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How about a loose-leaf Handbook?

Posted: 07 Mar 2016 01:00 PM PST
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A reader e-mailed me this morning with a comment on my recent blog post,
The ARRL really needs to reach out more effectively. He says,

I have been a life member for 46 years. The one thing I would like to see
is a loose-leaf handbook. I would buy the upgrades, but at the price the
charge for the book, buying a repeat of the same material does not make
sense.

I really like this idea. Not only would readers only have to pay for
material thats been added or updated, the ARRL could sell other loose-leaf
add-ins, such as logbook pages, lab notebook pages, Smith Chart pages,
pages that held QSL cards and award certificates, and other useful kinds of
things. A hams handbook would become not just a handbook, but alsoÂ*be his
or her own personal ham radio history.
WATSA, ARRL?

The post How about a loose-leaf Handbook? appeared first on KB6NUs Ham
Radio Blog.


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2016 Extra Class Study Guide: E3A - electromagnetic waves, propagation

Posted: 07 Mar 2016 12:05 PM PST
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E3A Electromagnetic waves; Earth-Moon-Earth communications; meteor
scatter; microwave tropospheric and scatter propagation; aurora propagation

An electromagnetic wave is a wave consisting of an electric field and a
magnetic field oscillating at right angles to each other. (E3A15) Saying
that changing electric and magnetic fields propagate the energy describes
how electromagnetic waves travel in free space. (E3A16)

An important characteristic of an electromagnetic wave is its polarization.
A wave is said to be vertically polarized if its electric field is
perpendicular to the Earth and horizontally polarized if the electric field
is parallel to the Earth. Waves with a rotating electric field are
circularly polarized electromagnetic waves. (E3A17)

Moon bounce, or Earth-Moon-Earth (EME) communication

One of the more exotic things that amateur radios do is earth-moon-earth
(EME) communication, sometimes called “moon bounce.� As this name implies,
radio amateurs actually bounce their signals off the moon. This is the
ultimate DX. The approximate maximum separation measured along the surface
of the Earth between two stations communicating by Moon bounce is 12,000
miles, if the Moon is visible by both. (E3A01)

Because the signal travels such a long way, you need to do everything you
can to avoid signal loss. So, for example, scheduling EME contacts when the
Moon is at perigee will generally result in the least path loss. (E3A03)
Perigee is the point at which the Moon is the closest to Earth.

One interesting phenomenon is libration fading. Libration fading of an
Earth-Moon-Earth signal is a fluttery, irregular fading. (E3A02) This
fading is caused by the irregular surface of the Moon, and the peaks can
last for up to two seconds on the 2m band. These peaks can actually help
operators make contacts when they would otherwise be impossible.

Because the signals are so weak, it’s also important to use equipment with
very low noise, so that the signals don’t fall below the noise level. That
being the case, the type of receiving system that is desirable for EME
communications is equipment with very low noise figures. (E3A04)

Meteor scatter

Some amateur radio operators bounce their signals off meteor trails. This
type of propagation is called meteor scatter. Meteor scatter propagation is
possible because when a meteor strikes the Earths atmosphere, a cylindrical
region of free electrons is formed at the E layer of the ionosphere.
(E3A08) 28 148 MHz is the frequency range that is well suited for
meteor-scatter communications. (E3A09)

Microwave tropospheric and scatter propagation

While HF propagation is not affected by weather conditions, the same cannot
be said for microwave propagation. Temperature inversion is the type of
atmospheric structure can create a path for microwave propagation. (E3A10)
These paths form in the troposhpere and and are often called tropospheric
ducts.

Tropospheric propagation of microwave signals often occurs along warm and
cold fronts. (E3A05) And, atmospheric ducts capable of propagating
microwave signals often form over bodies of water. (E3A07) The typical
range for tropospheric propagation of microwave signals is 1200 miles.
(E3A11)

Tropospheric propagation is quite predictable. There are even websites that
you can visit that will tell you where tropospheric ducts currently exist.
These websites include William Hepburns Radio & TV DX Information Centre
(http://www.dxinfocentre.com/tropo.html). This site shows where ducting is
occurring on Hepburn maps, which are maps that predict the probability of
tropospheric propagation. (E3A04)

Rain can also affect the propagation of microwave signals. The rain must be
within radio range of both stations for microwave propagation via rain
scatter. (E3A06)

Aurora propagation

Another interesting type of propagation is aurora propagation. The cause of
auroral activity—sometimes called the Northern Lights—is the interaction in
the E layer of charged particles from the Sun with the Earths magnetic
field. (E3A12)

From the contiguous 48 states, North is the approximate direction an
antenna should be pointed to take maximum advantage of aurora propagation.
(E3A14) CW is the emission mode that is best for aurora propagation. (E3A13)

The post 2016 Extra Class Study Guide: E3A electromagnetic waves,
propagation appeared first on KB6NUs Ham Radio Blog.