amateur extra license class

Amateur Extra License Class

Chapter 10Topics in Radio

Propagation

Solar Effects

• The sun has the biggest effect on HF propagation; even some effect on UHF and above

• The Internet is a key source of information for tracking these effects• Spaceweather.com• Hfradio.org• Swpc.noaa.gov

Solar Effects

• Solar flares• X-ray through Extreme UV (EUV) frequencies• Flare intensity: (lowest) A, B, C, M, X (highest)

• Within “X Flares” (X1, X2, X3, X4) radio blackouts probable

• An X3 flare is twice as intense as an X2

Solar Effects• Geomagnetic Field (GMF)

• Its disruption negatively affects the ionosphere and thus refraction

• Measurement parameters:• Bz : Interplanetary Magnetic Field (IMF): negative

number implies alignment of IMF and Earth’s field = disruption (Geomagnetic Field Stability)

• Southward orientation = greater likelihood of disturbance

• K index: Measure of disruption: 0 (quiet), 9 major storm)

Solar Effects• Geomagnetic Field (GMF)

• Its disruption negatively affects the ionosphere and thus refraction

• Measurement parameters:• A index: Average of last 9 K index readings, 0 to 400• G index: Derived from K and A indices: 0 (none), 1, 2, 3,

4, 5 (extreme)

Solar Effects• 304A

• NOAA reported value from 0 to unknown. Relative strength of total solar (UV) radiation at a wavelength of 304 angstroms (or 30.4 nm), emitted primarily by ionized helium in the sun's photosphere. Responsible for about half of all the ionization of the F layer in the ionosphere. This is correlated to solar flux Index.

Solar Effects

Most popular propagationIndices

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E3C10 – What does the 304A solar parameter measure?A. The ratio of X-Ray flux to radio flux, correlated

to sun spot numberB. UV emissions at 304 angstroms, correlated to

solar flux indexC. The solar wind velocity at 304 degrees for

tme solar equator, correlated to solar activityD. The solar emission at 304 GHz, correlated to

X-Ray flare levels

E3C07 – Which of the following descriptors indicates the greatest solar flare intensity?

A. Class AB. Class BC. Class MD. Class X

E3C09 – How does the intensity of an X3 flare compared to that of an X2 flare?

A. 10 percent greaterB. 50 percent greaterC. Twice as greatD. Four times as great

E3C04 – What does the value of Bz (B sub z) represent?

A. Geomagnetic field stabilityB. Critical frequency for vertical transmissionsC. Direction and strength of the interplanetary

magnetic fieldD. Duration of long-delayed echos

E3C05 – What orientation of Bz (B sub z) increases the likelihood that incoming particles from the Sun will cause disturbed conditions?A. SouthwardB. NorthwardC. EastwardD. Westward

E3C02 -- What is indicated by a rising A or K index?

A. Increasing disruption of the geomagnetic fieldB. Decreasing disruption of the geomagnetic

fieldC. Higher levels of solar UV radiationD. An increase in the critical frequency

E3C08 – What does the space weather term G5 mean?

A. An extreme geomagnetic stormB. Very low solar activityC. Moderate solar windD. Waning sunspot numbers

HF Propagation

• In nearly all cases, HF waves travel along the surface of the earth or they are returned to earth after encountering the upper layers of the ionosphere.

HF Propagation

• All types of waves can change direction due to two different phenomena:• Diffraction.

• Encountering a reflecting surface’s edge or corner.

• Refraction.• Change in velocity due to change in properties of

medium wave is traveling through.

HF Propagation

• Ground Wave• Special type of diffraction.

• Lower edge of wave (closest to the earth) loses energy due to induced ground currents.

• Lower edge slows, tilting wave front forward.• Primarily effects vertically-polarized waves.• Most noticeable on longer wavelengths.

• AM broadcast, 160m, & 80m.

• Over distance, ground wave signal is absorbed, decreasing strength.

• More pronounced at shorter wavelengths.• Most useful during daylight on 160m & 80m.

HF Propagation

• Sky Wave• Radio waves refracted in the E & F layers of the

ionosphere.• Maximum one-hop skip distance about 2500

miles.

HF Propagation

• Sky Wave• Pedersen Ray.

• High angle wave.• Provides propagation beyond normal maximum skip

distance.

HF Propagation• Sky Wave

• Chordal Hop• Successive ionospheric reflections without an

intermediate reflection from the ground• Significantly less loss from ground absorption

HF Propagation

• Sky Wave• Absorption.

• D layer.• Ionized only during sunlight.• Absorbs RF energy.

• The longer the wavelength, the more absorption.• Kills sky wave propagation on 160m & 80m during daylight

hours.

HF Propagation

• Extraordinary and Ordinary Waves• Linearly polarized waves are split into ordinary and

extraordinary waves• Independent waves created in the ionosphere that

are elliptically polarized.

HF Propagation

• Long Path and Gray Line• Long path.

• Radio waves travel a great-circle path between 2 stations.

• The path is shorter in one direction & longer in the other.

• The normal path is the shorter.• The long path is 180° from the short path.

HF Propagation

• Long Path and Gray Line• Long path.

• A slight echo on the received may indicate that long-path propagation is occurring.

• With long path propagation, the received signal may be stronger if antenna is pointed 180° away from the station.

• Long path propagation can occur on all MF & HF bands.• 160m through 10m.• Most often on 20m.

HF Propagation

• Long Path and Gray Line• Gray line propagation.

• At sunset, D layer collapses rapidly, reducing adsorption.

• F layer collapses more slowly.• Similar effect occurs at sunrise.• Net result is that long distance communications are

possible during twilight hours on the lower frequency bands.

• 8,000 to 10,000 miles.• 160m, 80m, 40m, & possibly 30m.

HF Propagation

• Long Path and Gray Line• Gray line propagation.

HF Propagation

• Fading• Variations in strength of received signals.

• Changes in height of ionized layers.• Changes in amount of absorption.• Random polarization shifts.• Multi-path reflections.

HF Propagation

• Fading• Selective fading.

• Fading can have a different effect signals that are only a few hundred Hertz apart.

• Can cause loss of mark or space signal of RTTY transmission.• Most severely affects wide-bandwidth signals such as AM or

FM.• Can cause moderate to severe distortion of received signal.

HF Propagation

• VOACAP• Voice of America Coverage Analysis Program• HF Propagation modeling software• Ray Tracing

• Modeling a radio wave’s path through the ionosphere

HF Propagation

• Solar Flares• Produce a sudden rise in radio background noise

HF Propagation

• K index: Measure of disruption: 0 (quiet), 9 major storm)

• A index: Average of last 9 K index readings, 0 to 400• Rising A and K indices indicate increasing

disruption of the geomagnetic field• Polar paths will experience high levels of

absorption

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

A. It stays the sameB. It increasesC. It decreasesD. It peaks at roughly 14 MHz

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

A. VerticalB. HorizontalC. CircularD. Elliptical

E3B12 – What is the primary characteristic of chordal hop propagation?

A. Propagation away from the great circle bearing between stations

B. Successive ionospheric reflections without an intermediate reflection from the ground

C. Propagation across the geomagnetic equatorD. Signals reflected back toward the transmitting

station

E3B13 – Why is chordal hop propagation desirable?

A. The signal experiences less loss along the path compared to normal skip propagation

B. The MUF for chordal hop propagation is much lower than for normal skip propagation

C. Atmospheric noise is lower in the direction of chordal hop propagation

D. Signals travel faster along ionospheric chords

E3B04 – What is meant by the terms extraordinary and ordinary waves?

A. Extraordinary waves describe rare long skip propagation compared to ordinary waves which travel shorter distances

B. Independent waves created in the ionosphere that are elliptically polarized

C. Long path and short path wavesD. Refracted rays and reflected waves

E3B14 – What happens to linearly polarized radio waves that split into ordinary and extraordinary waves in the ionosphere?

A. They are bent toward the magnetic polesB. Their polarization is randomly modifiedC. They become elliptically polarizedD. They become phase-locked

E3C11 – What does VOACAP software model?

A. AC voltage and impedanceB. VHF radio propagationC. HF propagationD. AC current and impedance

E3C01 – What does the term ray tracing describe in regard to radio communications?

A. The process in which an electronic display presents a pattern

B. Modeling a radio wave’s path through the ionosphere

C. Determining the radiation pattern from an array of antennas

D. Evaluating high voltage sources for X-Rays

E3C03 – Which of the following signal paths is most likely to experience high levels of absorption when the A index and K index is elevated?

A. Transequitorial propagationB. Polar pathsC. Sporadic-ED. NVIS

E3C15 – What might a sudden rise in radio background noise indicate?

A. A meteor pingB. A solar flare has occurredC. Increased transequitorial propagation likelyD. Long-path propagation is occurring

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

A. High D layer absorptionB. Meteor scatterC. Transmit frequency is higher than the MUFD. Receipt of a signal by more than one path

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

A. 160 to 40 metersB. 30 to 10 metersC. 160 to 10 metersD. 6 meters to 2 meters

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

A. 80 metersB. 20 metersC. 10 metersD. 6 meters

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

A. TransequatorialB. Sporadic-EC. Long-pathD. Gray-line

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

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

B. At twilight, D-layer absorption is low while E-layer and F-layer propagation remains high

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

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

Break

VHF/UHF/Microwave Propagation

• Auroral Propagation

VHF/UHF/Microwave Propagation

• Auroral Propagation• Charged particles from the sun (solar wind) are

concentrated over the magnetic poles by the earth’s magnetic field & ionize the E-layer.

• VHF & UHF propagation up to about 1,400 miles.

VHF/UHF/Microwave Propagation

• Sporadic-E Propagation• Occurs around the solstices – especially the

Summer Solstice• Can occur at any time of the day

VHF/UHF/Microwave Propagation

• Auroral Propagation• Reflections change rapidly.

• All signals sound fluttery.• SSB signals sound raspy.• CW signals sound like they are modulated with white

noise.• CW most effective mode.• Point antenna toward aurora, NOT towards

station.• In US, point antenna north.

VHF/UHF/Microwave Propagation

• Meteor Scatter Communications• Meteors passing through the ionosphere collide

with air molecules & strip off electrons.• Ionization occurs at or near the E-region.

• Best propagation 28 MHz to 148 MHz.• 20 MHz to 432 MHz possible.

VHF/UHF/Microwave Propagation

• Meteor Scatter Communications• Major meteor showers.

• Quadrantids January 3-5.• Lyrids – April 19-23.• Arietids – June 8.• Aquarids – July 26-31.• Perseids – July 27 to August 14.• Orionids – October 18-24.• Taurids – October 26 to November 16.• Leonids – November 14-16.• Geminids – December 10-14.• Ursids – December 22.

VHF/UHF/Microwave Propagation

• Meteor Scatter Communications• Operating techniques.

• Keep transmissions SHORT.• Divide each minute into four 15-second segments.

• Stations at west end of path transmit during 1st & 3rd segments.• Stations at east end of path transmit during 2nd & 4th

segments.

VHF/UHF/Microwave Propagation

• Meteor Scatter Communications• Operating techniques.

• Modes:• High Speed CW.

• 800-2,000 wpm.• Computer generated & decoded.

• Digital - FSK441 (part of WSJT software suite).• Repeated short bursts of data• Call Sign; Report

VHF/UHF/Microwave Propagation

• Above 30 MHz, radio waves are rarely refracted back to earth by the ionosphere.

• Must use other techniques for long-distance communications.

• Low-angle of radiation from the antenna is more important than on HF.

• It is more important for polarization of transmitting & receiving antennas to match than on HF.

VHF/UHF/Microwave Propagation

• Radio Horizon• Radio horizon not the same as visual horizon.

• Refraction in the atmosphere bends radio waves & increases “line-of-sight” distance by about 15%.

Visual Horizon (miles) ≈ 1.32 Hft

Radio Horizon (miles) ≈ 1.415 Hft

VHF/UHF/Microwave Propagation

• Multipath• Radio waves reflected off of many objects arrive at

receive antenna at different times.• Waves reinforce or cancel each other depending on

phase relationship.• Picket fencing.

• Rain scattering • microwave propagation • best observed around 10 GHz, but extends down to

a few gigahertz• This mode scatters signals mostly forwards and

backwards when using horizontal polarization and side-scattering with vertical polarization. Forward-scattering typically yields propagation ranges of 800 km (approx.500 miles).

• Rain must be w/in the radio range of both stations

VHF/UHF/Microwave Propagation

VHF/UHF/Microwave Propagation

• Tropospheric Propagation• VHF/UHF propagation normally limited to 500

miles.• Certain atmospheric conditions can create a

“duct” where radio waves can travel for hundreds or thousands of miles.

• Bands:• 6m – Rare.• 2m – Fairly common.• 70cm – Common.

VHF/UHF/Microwave Propagation

• Tropospheric Propagation• Temperature Inversion• Along Warm and Cold Fronts

VHF/UHF/Microwave Propagation

• Tropospheric Propagation• Hepburn Map:

0 1 2 3 4 5 6 7 8 9 10+

NIL SIG MARGINAL FAIR MODER

ATE GOOD STRONG

VERY STRONG

INTENSE

VERY INTENSE

EXTREME EXTREME

U = UNSTABLE SIGNAL AREAS

www.dxinfocentre.com/tropo.html

VHF/UHF/Microwave Propagation

• Transequatorial Propagation• Communications between stations located an

equal distance north & south of the magnetic equator.

VHF/UHF/Microwave Propagation

• Transequatorial Propagation• Most prevalent around the spring & autumn

equinoxes.• Maximum effect during afternoon & early evening.• Allows contacts up to about 5,000 miles.• Useable up to 2m & somewhat on 70cm.

• As frequency increases, paths more restricted to exactly equidistant from and perpendicular to the magnetic equator.

VHF/UHF/Microwave Propagation

• Earth-Moon-Earth (EME) Communications.• a.k.a. – Moon bounce.• If both stations can “see” the moon, they can talk.

• Maximum about 12,000 miles.

• Best when moon is at perigee.• 2 dB less path loss.

• Not useable near new moon.• Increased noise from the sun.

• The higher the moon is in the sky the better.

VHF/UHF/Microwave Propagation

• Earth-Moon-Earth (EME) Communications.• Low receiver noise figure essential.• Libration Fading.

• Caused by multipath effects of rough moon surface in combination with relative motion between the earth and the moon.

• Rapid, deep, irregular fading.• 20 dB or more.• Up to 10 Hz.• Can cause slow-speed CW to sound like high-speed CW.

VHF/UHF/Microwave Propagation

• Earth-Moon-Earth (EME) Communications.• Time synchronous transmissions alternately

from each station• 2m operation.

• 144.000 MHz to 144.100 MHz.• 2-minute schedule.

• Transmit for 2 minutes.• Receive for 2 minutes.

• Station farthest east transmits first then station to the west.

VHF/UHF/Microwave Propagation

• Earth-Moon-Earth (EME) Communications.• 70cm operation.

• 432.000 MHz to 432.100 MHz.• 2.5-minute schedule.

• Transmit for 2.5 minutes • Receive for 2.5 minutes.

• Station farthest east transmits first then station to the west.

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

A. E-region skipB. D-region skipC. Downward bending due to aurora refractionD. Downward bending due to density variations

in the atmosphere

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

A. By approximately 15% of the distanceB. By approximately twice the distanceC. By approximately one-half the distanceD. By approximately four times the distance

E3A05 – Tropospheric propagation of microwave signals often occurs along what weather related structure?A. Gray-lineB. Lightning dischargesC. Warm and cold frontsD. Sprites and jets

E3A10 -- Which type of atmospheric structure can create a path for microwave propagation?

A. The jet streamB. Temperature inversionC. Wind shearD. Dust devil

E3A07 – Atmospheric ducts capable of propagating microwave signals often form over what geographic feature?

A. Mountain rangesB. ForestsC. Bodies of waterD. Urban areas

E3A11 – What is a typical range for tropospheric propagation of microwave signals?

A. 10 miles to 50 milesB. 100 miles to 300 milesC. 1200 milesD. 2500 miles

E3A04 – What do Hepburn map predict?

A. Sporadic E propagationB. Locations of auroral reflecting zonesC. Likelihood of rain scatter along cold or warm

frontsD. Probability of tropospheric propagation

E3A06 – Which of the following is required for microwave propagation via rain scatter?

A. Rain droplets must be electrically chargedB. Rain droplets must be within the E layerC. The rain must be within radio range of both

stationsD. All of these choices are correct

E3B09 -- At what time of the year is Sporadic E propagation most likely to occur?

A. Around the solstices, especially the summer solstice

B. Around the solstices, especially the winter solstice

C. Around the equinoxes, especially the spring equinox

D. Around the equinoxes, especially the fall equinox

E3B11 – At what time of day is Sporadic-E propagation most likely to occur?

A. Around sunsetB. Around sunriseC. Early eveningD. Any time

E3B01 -- What is transequatorial propagation?

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

B. Propagation between any two points located on the magnetic equator

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

D. Propagation between two stations at the same latitude

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

A. MorningB. NoonC. Afternoon or early eveningD. Late at night

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

A. 1000 milesB. 2500 milesC. 5000 milesD. 7500 miles

E3A12 – What is the cause of auroral activity?

A. The interaction is the F2 layer between the solar wind and the Van Allen belt

B. A low sunspot level combined with tropospheric ducting

C. The interaction in the E layer of charged particles for the Sun with the Earth’s magnetic filed

D. Meteor showers concentrated in the extreme northern and southern latitudes

E3A13 – Which emission mode is best for auroral propagation?

A. CWB. SSBC. FMD. RTTY

E3A14 – From the contiguous 48 states, in which approximate direction should an antenna be pointed to take maximum advantage of aurora propagation?

A. SouthB. NorthC. EastD. West

E3A09 -- Which of the following frequency range is well suited for meteor scatter communications?

A. 1.8 - 1.9 MHzB. 10 - 14 MHzC. 28 - 148 MHzD. 220 - 450 MHz

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

A. The E layerB. The F1 layerC. The F2 layerD. The D layer

E2D02 – Which of the following is a good technique for making meteor scatter contacts?

A. 15 second times transmission sequences with station alternating base on location

B. Use of high speed CW or digital modesC. Short transmission with rapidly repeated call

sign and signal reportsD. All of these choices are correct

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

A. 500 miles, if the Moon is at perigeeB. 2000 miles, if the Moon is at apogeeC. 5000 miles, if the Moon is at perigeeD. 12,000 miles if the Moon is visible by both

stations

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

A. When the Moon is at perigeeB. When the Moon is fullC. When the Moon is at apogeeD. When the MUF is above 30 MHz

E3A02 -- What characterizes libration fading of an EME signal?

A. A slow change in the pitch of the CW signalB. A fluttery irregular fadingC. A gradual loss of signal as the Sun risesD. The returning echo is several hertz lower in

frequency than the transmitted signal

E2D06 -- Which of the following describes a method of establishing EME contacts?A. Time synchronous transmissions alternately

from each stationB. Storing and forwarding digital messagesC. Judging optimum transmission times by

monitoring beacons reflected from the Moon. D. High speed CW identification to avoid fading

Questions?