RADIO WAVE PROPAGATION
Propagation and technique: trans-equatorial, long path, gray-line; multi-path propagation
What is transequatorial propagation?
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Correct AnswerPropagation between two mid-latitude points at approximately the same distance north and south of the magnetic equator
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Propagation between any two points located on the magnetic equator
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Propagation between two continents by way of ducts along the magnetic equator
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Propagation between two stations at the same latitude
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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What is the approximate maximum range for signals using transequatorial propagation?
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1000 miles
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2500 miles
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Correct Answer5000 miles
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7500 miles
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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What is the best time of day for transequatorial propagation?
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Morning
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Noon
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Correct AnswerAfternoon or early evening
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Late at night
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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What type of propagation is probably occurring if an HF beam antenna must be pointed in a direction 180 degrees away from a station to receive the strongest signals?
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Correct AnswerLong-path
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Sporadic-E
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Transequatorial
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Auroral
Long path propagation can be confused with normal propagation when a beam has a significant lobe at 180 degrees to the main lobe. A real long path signal will have a significant delay, or echo, since it takes around 0.15 seconds for a signal to travel around the earth.
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Which amateur bands typically support long-path propagation?
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160 to 40 meters
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30 to 10 meters
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Correct Answer160 to 10 meters
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6 meters to 2 meters
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Which of the following amateur bands most frequently provides long-path propagation?
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80 meters
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Correct Answer20 meters
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10 meters
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6 meters
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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Which of the following could account for hearing an echo on the received signal of a distant station?
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High D layer absorption
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Meteor scatter
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Transmit frequency is higher than the MUF
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Correct AnswerReceipt of a signal by more than one path
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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What type of HF propagation is probably occurring if radio signals travel along the terminator between daylight and darkness?
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Transequatorial
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Sporadic-E
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Long-path
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Correct AnswerGray-line
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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At what time of day is gray-line propagation most likely to occur?
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Correct AnswerAt sunrise and sunset
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When the Sun is directly above the location of the transmitting station
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When the Sun is directly overhead at the middle of the communications path between the two stations
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When the Sun is directly above the location of the receiving station
Gray-line refers to the line (actually more of an area) between day and night that circles the earth. Transmitting at sunrise or sunset you can take advantage of the special atmospheric properties that exist on that gray line.
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What is the cause of gray-line propagation?
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At midday, the Sun being directly overhead superheats the ionosphere causing increased refraction of radio waves
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Correct AnswerAt twilight, D-layer absorption drops while E-layer and F-layer propagation remain strong
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In darkness, solar absorption drops greatly while atmospheric ionization remains steady
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At mid afternoon, the Sun heats the ionosphere decreasing radio wave refraction and the MUF
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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Which of the following describes gray-line propagation?
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Backscatter contacts on the 10 meter band
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Over the horizon propagation on the 6 and 2 meter bands
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Correct AnswerLong distance communications at twilight on frequencies less than 15 MHz
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Tropospheric propagation on the 2 meter and 70 centimeter bands
Gray-line Importance to Propagation Special ionospheric propagation conditions often exist between two or more stations simultaneously located on the gray-line transition between daylight and darkness.
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