Radio Wave Propagation
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Topic E3: Radio Wave Propagation


E3A-2012: Propagation and technique, Earth-Moon-Earth communications; meteor scatter

E3A01-2012: What is the approximate maximum separation measured along the surface of the Earth between two stations communicating by Moon bounce?

12,000 miles, as long as both can "see" the Moon

500 miles, if the Moon is at perigee

2000 miles, if the Moon is at apogee

5000 miles, if the Moon is at perigee



E3A02-2012: What characterizes libration fading of an Earth-Moon-Earth signal?

A fluttery irregular fading

A slow change in the pitch of the CW signal

A gradual loss of signal as the Sun rises

The returning echo is several Hertz lower in frequency than the transmitted signal



E3A03-2012: When scheduling EME contacts, which of these conditions will generally result in the least path loss?

When the Moon is at perigee

When the Moon is full

When the Moon is at apogee

When the MUF is above 30 MHz



E3A04-2012: What type of receiving system is desirable for EME communications?

Equipment with very low noise figures

Equipment with very wide bandwidth

Equipment with very low dynamic range

Equipment with very low gain



E3A05-2012: Which of the following describes a method of establishing EME contacts?

Time synchronous transmissions with each station alternating

Storing and forwarding digital messages

Judging optimum transmission times by monitoring beacons from the Moon

High speed CW identification to avoid fading



E3A06-2012: What frequency range would you normally tune to find EME signals in the 2 meter band?

144.000 - 144.100 MHz

144.000 - 144.001 MHz

144.100 - 144.300 MHz

145.000 - 145.100 MHz



E3A07-2012: What frequency range would you normally tune to find EME signals in the 70 cm band?

432.000 - 432.100 MHz

430.000 - 430.150 MHz

430.100 - 431.100 MHz

431.100 - 431.200 MHz



E3A08-2012: When a meteor strikes the Earth's atmosphere, a cylindrical region of free electrons is formed at what layer of the ionosphere?

The E layer

The F1 layer

The F2 layer

The D layer



E3A09-2012: Which of the following frequency ranges is well suited for meteor-scatter communications?

28 - 148 MHz

1.8 - 1.9 MHz

10 - 14 MHz

220 - 450 MHz



E3A10-2012: Which of the following is a good technique for making meteor-scatter contacts?

All of these choices are correct

15 second timed transmission sequences with stations alternating based on location

Use of high speed CW or digital modes

Short transmission with rapidly repeated call signs and signal reports






E3B-2012: Propagation and technique, trans-equatorial; long path; gray-line; multi-path propagation

E3B01-2012: What is transequatorial propagation?

Propagation between two mid-latitude points at approximately the same distance north and south of the magnetic equator

Propagation between any two points located on the magnetic equator

Propagation between two continents by way of ducts along the magnetic equator

Propagation between two stations at the same latitude



E3B02-2012: What is the approximate maximum range for signals using transequatorial propagation?

5000 miles

1000 miles

2500 miles

7500 miles



E3B03-2012: What is the best time of day for transequatorial propagation?

Afternoon or early evening

Morning

Noon

Late at night



E3B04-2012: 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?

Long-path

Sporadic-E

Transequatorial

Auroral



E3B05-2012: Which amateur bands typically support long-path propagation?

160 to 10 meters

160 to 40 meters

30 to 10 meters

6 meters to 2 meters



E3B06-2012: Which of the following amateur bands most frequently provides long-path propagation?

20 meters

80 meters

10 meters

6 meters



E3B07-2012: Which of the following could account for hearing an echo on the received signal of a distant station?

Receipt of a signal by more than one path

High D layer absorption

Meteor scatter

Transmit frequency is higher than the MUF



E3B08-2012: What type of HF propagation is probably occurring if radio signals travel along the terminator between daylight and darkness?

Gray-line

Transequatorial

Sporadic-E

Long-path



E3B09-2012: At what time of day is gray-line propagation most likely to occur?

At sunrise and sunset

When the Sun is directly above the location of the transmitting station

When the Sun is directly overhead at the middle of the communications path between the two stations

When the Sun is directly above the location of the receiving station



E3B10-2012: What is the cause of gray-line propagation?

At twilight, D-layer absorption drops while E-layer and F-layer propagation remain strong

At midday, the Sun being directly overhead superheats the ionosphere causing increased refraction of radio waves

In darkness, solar absorption drops greatly while atmospheric ionization remains steady

At mid afternoon, the Sun heats the ionosphere decreasing radio wave refraction and the MUF



E3B11-2012: Which of the following describes gray-line propagation?

Long distance communications at twilight on frequencies less than 15 MHz

Backscatter contacts on the 10 meter band

Over the horizon propagation on the 6 and 2 meter bands

Tropospheric propagation on the 2 meter and 70 centimeter bands






E3C-2012: Propagation and technique, Aurora propagation; selective fading; radio-path horizon; take-off angle over flat or sloping terrain; effects of ground on propagation; less common propagation modes

E3C01-2012: Which of the following effects does Aurora activity have on radio communications?

All of these choices are correct

SSB signals are raspy

Signals propagating through the Aurora are fluttery

CW signals appear to be modulated by white noise



E3C02-2012: What is the cause of Aurora activity?

The interaction of charged particles from the Sun with the Earth's magnetic field and the ionosphere

The interaction between the solar wind and the Van Allen belt

A low sunspot level combined with tropospheric ducting

Meteor showers concentrated in the northern latitudes



E3C03-2012: Where in the ionosphere does Aurora activity occur?

In the E-region

In the F1-region

In the F2-region

In the D-region



E3C04-2012: Which emission mode is best for Aurora propagation?

CW

SSB

FM

RTTY



E3C05-2012: Which of the following describes selective fading?

Partial cancellation of some frequencies within the received pass band

Variability of signal strength with beam heading

Sideband inversion within the ionosphere

Degradation of signal strength due to backscatter



E3C06-2012: By how much does the VHF/UHF radio-path horizon distance exceed the geometric horizon?

By approximately 15% of the distance

By approximately twice the distance

By approximately one-half the distance

By approximately four times the distance



E3C07-2012: How does the radiation pattern of a horizontally polarized 3-element beam antenna vary with its height above ground?

The main lobe takeoff angle decreases with increasing height

The main lobe takeoff angle increases with increasing height

The horizontal beam width increases with height

The horizontal beam width decreases with height



E3C08-2012: What is the name of the high-angle wave in HF propagation that travels for some distance within the F2 region?

Pedersen ray

Oblique-angle ray

Ordinary ray

Heaviside ray



E3C09-2012: Which of the following is usually responsible for causing VHF signals to propagate for hundreds of miles?

Tropospheric ducting

D-region absorption

Faraday rotation

Ground wave



E3C10-2012: How does the performance of a horizontally polarized antenna mounted on the side of a hill compare with the same antenna mounted on flat ground?

The main lobe takeoff angle decreases in the downhill direction

The main lobe takeoff angle increases in the downhill direction

The horizontal beam width decreases in the downhill direction

The horizontal beam width increases in the uphill direction



E3C11-2012: From the contiguous 48 states, in which approximate direction should an antenna be pointed to take maximum advantage of aurora propagation?

North

South

East

West



E3C12-2012: How does the maximum distance of ground-wave propagation change when the signal frequency is increased?

It decreases

It stays the same

It increases

It peaks at roughly 14 MHz



E3C13-2012: What type of polarization is best for ground-wave propagation?

Vertical

Horizontal

Circular

Elliptical



E3C14-2012: Why does the radio-path horizon distance exceed the geometric horizon?

Downward bending due to density variations in the atmosphere

E-region skip

D-region skip

Downward bending due to aurora refraction





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