This propagation mode can provide contact from 28-432 MHz. It is thought to be due to irregularities in the F-Layer above the equator bending and reflecting the signals. (drichmond60)

Hint: The prefix trans- means across (or, in chemistry, on opposite sides).

Hint2: long word longest answer

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The transequitorial propagation (TEP) mode can provide contact from 28-432 MHz. It is thought to be due to irregularities in the F-Layer above the equator bending and reflecting the signals. The transmit and receive stations have to be approximately equidistant from and on opposite sides of the equator.

Memory tip: Stations have to be approximately the same distance from the equator, so the equator splits the total distance between them 50/50 (or 50%). Pick the answer that starts with 50 (5000 miles).

Memory tip: Remember the song "I will walk 500 miles and I will walk 500 more." Multiply by 10, and If you know that 80s song you will remember this answer of 5000.

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Afternoon and Evening Trans-equatorial Propagation are two distinctly different types of Trans-equatorial Propagation.

Afternoon Trans-equatorial Propagation peaks during the mid-afternoon and early evening hours and is generally limited to distances of 4,000–5,000 miles. Signals propagated by this mode are limited to approximately 60 MHz. Afternoon Trans-equatorial Propagation signals tend to have high signal strength and suffer moderate distortion due to multipath reflections.

Evening Trans-equatorial Propagation peaks in the evening around 1900 to 2300 hours local time. Signals are possible up to 220 MHz, and even very rarely on 432 MHz. Evening Trans-equatorial Propagation is quenched by moderate to severe geomagnetic disturbances. The occurrence of evening Trans-equatorial Propagation is more heavily dependent on high solar activity than is the afternoon type. www.wikipedia.org

Memory tip: Signal is crossing over the tropics. When's the best time to enjoy a tropical cocktail? Afternoon or early evening!

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A radio wave entering an ionized region like the ionosphere in which there is also a magnetic field, will split into two waves which are elliptically polarized with their E field at right angles to each other. These are the extraordinary and ordinary waves that may take separate paths to the receiver.

The ordinary wave, or o-wave has an electrical field oriented parallel to the Earth's magnetic field. The extraordinary wave, or x-wave has an electrical field oriented perpendicular to the Earth's magnetic field. The waves also travel at different speeds, creating a phase difference between them. Above 10 MHz, the two waves travel nearly identical paths. At 7 MHz and below, the two waves can travel different paths and in different directions.

Hint: "Extraordinary" and "Elliptical" both start with the letter E

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If you're asking: "How typical is typical?" then you're overthinking it.

Without thinking about where we are in the sunspot cycle or what time of day or year it is, then which bands might potentially carry your signal the long way around the planet?

Any HF band or 160m might work.

It would be highly atypical for 6m or 2m to be open in such a way.

Silly memory tip Long-path: long range So 160 to 10 is the longest range.

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Because DX working is relatively easy on the 20 meter band, it tends to be the most congested of the HF bands. Propagation is primarily via the F2 layer, which can remain intact for most of the 24-hour cycle under solar maximum conditions.

Hint: for 2 of us to play long distance =20meter

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Particularly when using HF there may be more than one propagation path that the signal can take to get from the distant station to your receiver. RF signals travel at the speed of light, but if the distance is great enough there can be an audible delay between the two signals.

Your receiver receives signals from both paths, thus causing the echo.

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Along the twilight region the absorption of signals by the D layer rapidly ceases while the E- and F-layers remain for a while with an MUF of up to 5MHz. This gives a region of enhanced 1.8MHz and 3.6MHz propagation called the Gray line, which forms an approximate great circle. For each station the time for the Gray line to pass by is in the order of minutes and the direction of enhanced propagation is along the Gray line, in other words approximately north and south.

Hint: Think of the twilight region as the gray area between light and dark.

Hint2: Think White(light)+Black(Dark) colors when mixed produce "Gray"

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Sporadic E displays seasonal patterns. Sporadic E activity peaks predictably in the summertime. In North America, the peak is most noticeable in mid-to-late June (e.g. near the summer solstice), trailing off through July and into August. A much smaller peak is seen around the winter solstice. https://en.wikipedia.org/wiki/Sporadic_E_propagation

Silly hint: when the kids are off from school, in summer, their schedule tends to be more sporadic.

Alternative silly hint: Sporadic and summer solstice are alliterative.

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Along the twilight region the absorption of signals by the D layer rapidly ceases while the E- and F-layers remain for a while with an MUF of up to 5MHz. This gives a region of enhanced 1.8MHz and 3.6MHz propagation called the Gray line, which forms an approximate great circle. For each station the time for the Gray line to pass by is in the order of minutes and the direction of enhanced propagation is along the Gray line, in other words approximately north and south.

Hint: Think of Gray as Twilight time. Only one answer has Twilight in it.

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A Helpful Mnemonic: It is precisely because this sort of propogation is sporadic is why it can occur at ANY time!!

For more detailed explanation, check out the wiki article about Sporadic E Propagation

Silly Hint: When? N-"E" time (Anytime for Sporadic E Propogation)

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When a signal approaches the ionosphere at a steep angle the signal penetrates the ionosphere and may pass right through, or be 'reflected' back (green ray, right). It is actually refracted rather than reflected. However, when a signal approaches the ionosphere at a grazing angle, the likelihood of 'reflection' is higher than for vertically approaching signals. The penetration is less and the attenuation is less. Further, if the angle is low enough, the signal can be reflected again off the ionosphere without first hitting the ground (red ray, right).

This 'chordal hop' process is believed to be common at night when the F layer is stable. Because there is no ground reflection involved, and less penetration of the ionosphere, the attenuation is much less than with other propagation mechanisms, and as a result signals are stronger. In order to enhance the possibility of Chordal Hop, it is important to make use of antennas with the lowest possible beam elevation, to ensure that the signal hits the ionosphere as far from the transmitter as possible.

Hint: The correct answer is the only one that mentions the ground in it.

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Here's a simple explanation with a picture:

http://www.qsl.net/sv1uy/chordal-hop.html

Normally, you'd expect HF radio waves to bounce between the Earth and the ionosphere, up and down, being partially absorbed, refracted, and diffused in every direction, which decreases received signal strength. Hopefully, enough is reflected that the transmitter can be heard.

With chordal hop propagation, some of the radio waves encounter the ionosphere at an angle where they are given a few chance to skip off of the ionosphere one or more times in a row without skipping off of the Earth, which decreases losses along that path.

Test Hint: There are no chords in the right answer.

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The radio wave splits into two waves called the extraordinary wave and the ordinary wave when it enters the ionosphere.

The terms ordinary and extraordinary waves describe the independent waves created in the ionosphere that are elliptically polarized.

Hint: the correct answer is the only one that contains the word "polarized."

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