1. High Frequency Propagation
Presented by K3LR
Dayton 2015

2. The Sun’s Place in our Galaxy
Our Sun is just one of hundreds of billions of stars in the Milky Way
The galaxy in the image is similar to what we believe the Milky Way looks like from a distance.
Our Sun resides about 28,000 light years from the super massive black hole at the Milky Way’s galactic center

3. Overview of Propagation-Related Solar Effects
Sunspots
More sunspots during the sunspot peak improve 15, 12, 10 and 6 meter propagation especially from October through May
Sunspot cycles vary in length from 9 to 14 years
Some cycles have longer lasting, more energetic maximums
Some cycles have longer lasting, deeper minimums
Fast moving electromagnetic radiation from solar flares
Ultraviolet radiation and X-rays arrive at Earth in only 8 minutes
Particle emissions from coronal holes, solar flares and CMEs
Energetic charged particles pulled into the Earth's polar regions by its magnetic field cause geomagnetic storms and aurora
Solar rotation causes repetitive and predictable solar events
Full rotation takes approximately 27 days
Seasonal variations on Earth caused by its 23.5 degree tilt
The Earth's tilt varies the total amount of solar radiation received, especially in the Earth's polar regions
Total solar radiation on Earth: kilowatts per square meter
Sunspot activity has a major effect on long distance radio communications particularly on the shortwave bands although medium wave and low VHF frequencies are also affected. High levels of sunspot activity lead to improved signal propagation on higher frequency bands, although they also increase the levels of solar noise and ionospheric disturbances. These effects are caused by impact of the increased level of solar radiation on the ionosphere.

4. Sunspots and the Sunspot Cycle

5. Sunspots are regions of strong magnetic fields
They appear dark because they are cooler than the surface
When you safely look at the Sun (i.e. through special filters) you see dark spots on the solar disk, as in the image at upper left.. These “sunspots” can range in size from 2500 km to over 50,000 km (many Earth diameters) across. Caused by intense magnetic fields emerging from the interior, a sunspot appears to be dark because it is slightly cooler than the rest of the solar surface. If you took a sunspot away from the Sun and held it up in the sky, it would glow very brightly!.
[movie on upper right]
A sunspot usually denotes a magnetically active region on the Sun. These active regions are dominated by strong magnetic areas where a concentrated portion of the solar magnetic field pokes through the surface layers. Active regions are also responsible for solar flares, prominences, coronal mass ejections, and other solar disturbances. These regions are cooler than the rest of the solar surface because the strong magnetic fields inhibit the escape of heat from the regions.
[movie lower left]
Sunspots can exist separately or in sunspot groups. Long-lived sunspots can last up to several months, but most survive only a matter of days. Sunspots are constantly changing due to the fluctuating magnetic fields. The movie shows an active region as seen by SOHO/MDI. This region hosted an exceptionally large sunspot group observed on 30 March The sunspot area spanned more than 13 times the entire surface of the Earth!  This spot was the source of an exceptionally large flare recorded on 2 April 2001.
Image Credits: SOHO/MDI. SOHO is a project of international cooperation between ESA and NASA.
Movie Files: DOT_SU~1.MPG
sunspotgrowth.avi

6. The Sunspot Number The oldest measure of solar activity
Continuous records since the early 19th century
Computed by multiplying the number of observed sunspot groups by 10 and adding the number of individual spots observed
Because the sun rotates and different areas of the sun are visible each day, average sunspot numbers are normally used
The lowest possible sunspot number is 0
Higher sunspot numbers equate to more solar activity
The largest annual average sunspot number of occurred in 1957

7. Actual solar cycle length varies from 9 to 14 years
The 11 Year Sunspot Cycle
Actual solar cycle length varies from 9 to 14 years
The amount of magnetic activity on the Sun varies in an approximate 11 year cycle. That is, the Sun will be covered with sunspots and activity at Solar Maximum, the number of spots will decline to Solar Minimum, and then climb back up again. This process takes about 11 years to complete. It is not a perfectly regular cycle, some peaks are higher, some lower.
In 1848 Rudolph Wolf devised a daily method of estimating solar activity by counting the number of individual sunspots and groups of spots on the face of the Sun. Wolf chose to compute his sunspot number by adding 10 times the number of groups to the total count of individual spots, because neither quantity alone completely captured the level of activity. Today, Wolf sunspot counts continue since no other index of the Sun's activity reaches into the past as far and as continuously. The chart at the bottom of the slide lists the Sunspot Numbers from the 1600s to the present. (See
It is strongly suspected that solar activity can dramatically affect climate on Earth.. Note on the chart that the sunspots disappeared for approximately 70 years during the late 1600s. It was during this time that Europe experienced its Little Ice Age, a period of severely cold weather, increased glaciation, and freezing storms that had a devastating impact on agriculture, health, economics, social strife, emigration, and even art and literature. There is evidence that the Sun has had similar periods of inactivity, with associated changes in Earth’s climate, in the more distant past. The connection between solar activity and terrestrial climate is an area of on-going research.
Nobody understands why there is a solar cycle nor why it behaves the way it does. Its one of the more interesting questions scientists are studying about the Sun.
The current cycle called cycle 23 passed its peak in 2001 with a few periods of high activity in 2002 and We are gradually declining to an eventual solar minimum expected sometime in 2007.
Presenter: get the latest sunspot number prediction plot from the following site, it is updated monthly.
Image Credits: Yohkoh image of Sun in X-rays. NASA. Used in a press release of 18 January (

8. Sunspots appear at different latitudes throughout the solar cycle
June 12, 2000
Sunspots do not appear at random over the surface of the Sun but are concentrated in two latitude bands on either side of the equator. The “butterfly” shaped diagram shows the positions of sunspots for each rotation of the Sun since May The diagram shows that these bands first form at mid-latitudes, widen, and then move toward the equator as each cycle progresses. Over the course of a solar cycle, newly formed sunspots appear closer and closer to the equator. But just before spots would appear at the equator, a new solar cycle begins, with sunspots popping up once again in the higher latitudes of the solar disk. The mechanisms of the solar cycle are only partially understood.
Image credits: “Butterfly” diagram from NASA/Marshall Space Flight Center. Most likely Dave Hathaway.
unknown
Jan 7, 2004

9. 400 Years of Sunspot Observations 55 years of unusually high sunspot activity 1947 - 2002
ended with the decline of Solar Cycle 23 in 2002
Dalton Minimum
30 years
Early 20th century minimum
20 years
Modern Maximum
55 years
Maunder Minimum
70 years

10. Steadily Weakening Sunspot Activity Since Solar Cycle 22

11. Solar Cycle Progress Since the Solar Cycle 23 Maximum
End of the 55 year Modern Maximum
2002
1st peak
Nov 2011
2nd peak
Feb 2014
Solar
minimum
about 2020
Sunspot Number
266 spotless
days during
2008

12. Solar Radiation and Emissions. Solar wind. Coronal holes. Solar flares
Solar Radiation and Emissions Solar wind Coronal holes Solar flares Coronal mass ejections (CMEs)

13. The Quiet and Active Sun
These movies in extreme ultraviolet wavelengths show what a small difference 3 years can make in solar magnetic activity during the solar cycle. The left image shows a very quiet solar disk taken around solar minimum. The right image shows a marked increase in solar activity just a few years later.
These images were taken by an instrument sensitive only to ultraviolet (UV) wavelengths of light Because our eyes cannot “see:’ UV light, the scientists have colored the Sun neon green to denote a non-visible wavelength.
Image Credits: SOHO/EIT. SOHO is a project of international cooperation between ESA and NASA
Movie File: 9699.MPG
Major changes in solar activity over just a three year span

14. Eruptions are common during periods of high solar activity
Solar Eruptions
Eruptions are common during periods of high solar activity
The Sun is capable of sudden and dramatic behavior that can severely impact the Earth’s magnetosphere and upper atmopshere. The movie shows a flare that disrupted communications on Earth. (Note in the movie how high energy particulars from the flare impact the camera.)
A solar flare occurs when magnetic energy that has built up in the solar atmosphere is suddenly released. Flares appear as sudden, rapid, and intense variations in brightness. The amount of energy released is the equivalent of millions of 100-megaton hydrogen bombs exploding at once!
Filaments are large regions of very dense, cooler gas held in place by magnetic fields. From the Earth’s vantage point, they usually appear as long and thin dark lines above the surface of the Sun. If we happen to view filaments on the "edge" or limb of the Sun, as in the image at left, they exhibit an arched appearance and we call them prominences. They can remain visible for many hours.
Image credits:
SOHO/EIT Category X17.2 flare from Tuesday 28 October 2003.
Prominence image also courtesy of SOHO/EIT consortium. SOHO is a project of international cooperation between ESA and NASA.
Movie File: eit195c.mpg
Huge flare of 28 October 2003
Solar prominence dwarfs Earth in size

15. Solar Flares massive explosions on the Sun’s surface
In just a few minutes they heat solar gasses to millions of degrees Fahrenheit and release as much energy as billions of megatons of TNT
Images from NASA’s SOHO Spacecraft

16. Solar Flares A plume of very hot gas ejected from the Sun’s surface
They rise through the chromosphere into the corona, disturbing both regions
Emits very large quantities energetic protons
Flares are so hot -- more than a million degrees Fahrenheit – that they also emit lots of x-ray radiation that travels to Earth in only 8 minutes
Solar flares are very difficult to predict
Solar flares occur during all phases of the solar cycle

17. Coronal Mass Ejections Huge Explosions on the Sun
Billions of tons per second of energetic charged particles are launched from the Sun
Sometimes when magnetic fields break on the Sun, large globs of hot plasma with magnetic fields trapped in them are ejected into space. These events, called Coronal Mass Ejections (CMEs), can launch a billion tons of material – somewhat like Mount Everest being vaporized and shot out into space!
The magnetic fields trapped in a CME can cause a huge impact if they hit the Earth’s magnetosphere just right.
In the images, taken by instruments on the SOHO spacecraft, a metal disk blocks out the bright Sun to allow us to see the dimmer outer corona. The diameter of the Sun is represented by the white round circle in the center. This will give you a sense of scale of the size of these CME’s in comparison to the Sun.
The movie on left is a closeup spanning 7.5 hours showing a large CME.
The movie on the right is a wide angle shot in slow motion of the same CME but spanning 20 hours. We’ve dubbed this particular CME event, “the light bulb” because of its similar shape.
Image credits: SOHO/LASCO. SOHO is a project of international cooperation between ESA and NASA.
Movie File: C2_lightbulbs.mpg
lascobulb.avi

18. How solar emissions affect the Earth

19. 27 day Recurrence of Propagation Effects
caused by the Sun’s 27 day solar rotation period
The actual solar rotation period varies significantly with solar latitude
The Sun does not rotate as a rigid sphere like the Earth
Its equator rotates much faster than its high latitude regions

20. Variability of Received Solar Energy Due to the Tilt of the Earth's Axis Increased ionization during the Spring and Fall equinoxes Less frequent and lower intensity geomagnetic storms during the Summer and Winter solstices

21. Sudden Ionospheric Disturbance (SID)
SIDs occur only during daylight hours SIDs strongly ionize the D layer causing dramatically increased absorption of signals up to 30 MHz propagated via the ionosphere Disrupts signals on lower frequencies for a longer duration than on higher frequencies but it can wipe out ionospheric communication on all of the HF bands Propagation returns to pre-SID levels within about an hour

22. Best time to view the aurora is around midnight in a dark location
Intensity and latitude of the aurora depend on the strength of the geomagnetic storm that caused it
Best time to view the aurora is around midnight in a dark location
The aurora is rarely visible at mid-Atlantic latitudes G1 G3 G5

23. The Ionosphere

24. The Ionospheric Layers
The key points are the D, E and F layers. The F layer splits and becomes F1 and F2 with the additional energy from the daytime sun. The D and E layers disappear at night without the sun’s energy. The D layer absorbs most RF power, particularly at low frequencies. The other layers will reflect RF energy. The higher the layer, the further the contact possible.
Propagation conditions are a balance between the D layer absorption of lower frequencies and the reflection of the higher frequencies by the upper layers. As more of the sun’s energy (primarily electromagnetic and particle emissions) strikes the ionosphere, all the layers grown in size and density. The D layer will absorb more low frequency RF and the upper layers will reflect more high frequency RF. This creates a window of frequencies above the Lowest Usable Frequency (LUF) and Maximum Usable Frequency (MUF) that will work for long distance communications.
Sunspots provide huge amounts of energy to reflect radio waves in the ionosphere and are especially important in the upper bands. The sun rotates (solar day) every 28 days. This means if conditions are good on one day, they are likely to repeat 28 days later when the earth is in the same position.
Because the sun is so critical for communications, measurements are constantly being made of the “Solar Flux” (RF energy emitted by the sun). In the US, WWV broadcasts reports with the “Solar Flux Index” (a measure of solar activity that is taken at a specific frequency) every hour.

25. The Ionospheric Layers
About 60 km (40 miles) above us lies a desolate place where continual blasts of particles and energy from the Sun hit our atmosphere so strongly that electrons are stripped away from their nuclei. This "ionized" region, where electrons and nuclei run around freely, is a plasma we call the ionosphere.
The free electrons in the ionosphere have a strong influence on the propagation of radio signals. Radio frequencies of very long wavelength (very low frequency or VLF) "bounce" back off electrons in the ionosphere thus, conveniently for us, allowing radio communication "over the horizon" and around our curved Earth.
The ionosphere reacts strongly to the intense X-ray and ultraviolet radiation released by the Sun during a solar flare, solar storm, or coronal mass ejection. The density of the particles in the ionosphere is altered during such a storm, changing the waves’ ability to bounce and resulting in intermittent static or loss of reception from distant communication stations.
Image Credits: unknown

26. D Layer of the Ionosphere
Strongly absorbs lower HF frequencies during the day
During daylight hours the D layer absorbs essentially all ionospheric propagation below 4 MHz
Absorption extends up to 30 MHz during SIDs and intense geomagnetic storms
The D layer totally disappears at sunset, making reliable worldwide 80 and 160 meter DX propagation possible
80 km height

27. E Layer of the Ionosphere
Densely ionized during the day
Reliably refracts 40 and 30 meter signals during daylight hours at distances less than 500 miles
Blankets F layer propagation on 40 and meters during the day
E layer MUF rapidly drops rapidly after sunset
Sporadic-E Ionization
Thin patches of intense ionization
Mainly useful for 10, 6 and 2 meter propagation
Sporadic-E usually lasts a few hours or less
Very difficult to forecast
Occurs very frequently during June and July
~ 120 km height

28. F Layers of the Ionosphere
The F Layers are the highest layers and provide highly reliable DX propagation
During the day the F layer ionizes into two distinct layers:
F1 layer at 200 km
F2 layer at 300 – 400 km
At night the two layers combine into a single less intensely ionized F-layer
Single-hop F2 provides propagation up to 2500 miles
Multi-hop F2 provides world wide coverage
Long path F2 propagation is common of 40 and 20 meters in the afternoon
~200 – 400 km height

29. Day and Night Ionospheric Layers
< Daytime
Night-time >
D layer vanishes at sunset
E layer MUF drops rapidly after sunset
F1 and F2 layers merge and remain ionized overnight but with much lower MUF especially during the winter
The D, E, F1 and F2 layers are ionized during the day

30. Day and Night Variation of the Ionosphere
The F layer is the primary layer for reflecting DX signals
Ionization varies with the time of day, season, geomagnetic storms and sunspot cycle
Ionization is greatest during daylight hours
Because it expands when heated, the F layer has significantly less ionization density during July and August
The F1 and F2 layers merge at night, but the F-region is significantly weaker at night causing significantly reduced MUFs especially during winter
Night-time
Daytime

31. Ionospheric Propagation
Ionospheric Layers
The D layer absorbs frequencies below about 5 MHz during the day
The E layer reflects radio waves below about 15 MHz during the day
The F layers refracts radio waves below about 30 MHz
Refraction via the ionosphere
E layer propagation covers a ground range of 1200 miles
Single hop F layer propagation covers a ground range of 2500 miles
Multi-hop F layer propagation provides worldwide coverage including long paths of more than 12,000 miles
Lowest Usable Frequency (LUF)
D layer absorption primarily determines the LUF
Maximum Usable Frequency (MUF)
E and especially F layer refraction determines the MUF

32. Measures of the Daily Intensity of Solar Radiation affecting the Ionosphere
Solar Flux
the sun’s radiation measured at 10.7cm wavelength
it is not a direct measure of ionizing UV radiation but its usually very well correlated to the intensity of UV radiation
K-index
quantifies disturbances to the Earth's magnetic field caused by solar emissions during the prior 3 hour interval
an integer in the range from 0 to 9
0-2 being quiet and 5 or more indicating geomagnetic storms of increasing intensity
A-index
the 24 hour daily average level of geomagnetic activity for the previous day (2100Z-2100Z)
The label 'K' origins from German 'Kennziffer' meaning 'characteristic digit'.

33. Propagation Indices – the K Index
A localized index of geomagnetic activity computed every three hours at many points on Earth. The K scale is shown below
The most reliable HF propagation occurs when K is 3 or less. 160 and 80 meter propagation are often enhanced when the K is 2 or less
K Index
Geomagnetic Condition
Inactive 1
Very Quiet 2
Quiet 3
Unsettled 4
Active 5
Minor Storm 6
Major Storm 7
Severe Storm 8
Very Severe Storm 9
Extremely Severe Storm

34. Propagation Indices – the Ap Index
A 24 hour average planetary geomagnetic activity index based on local K indices, updated daily at 2100Z The Ap Index scale is shown below:
Good HF propagation is likely when A is less than 15, particularly on the lower HF band
Ap Index
Geomagnetic Condition
0-7
Quiet
8-15
Unsettled
16-29
Active
30-49
Minor Storm
50-99
Major Storm
Severe Storm

35. HF Propagation Modes

36. HF Propagation Modes Three fundamental HF propagation modes:
Ground wave: vertically polarized local propagation on 160 and 80 meters only
Surface or space wave: propagation extending somewhat beyond the line of sight
Sky wave: all propagation via the ionosphere

37. Critical Frequency
The highest frequency that returns to Earth via directly overhead propagation
Dependent on the level of ionization directly overhead
Usually measured by ionospheric sounders
Typical critical frequencies are:
Summer day: 9 MHz Summer night: 4 MHz
Winter day: 14 MHz Winter night: MHz
Near Vertical Incidence Skywave (NVIS) uses frequencies below the critical frequency to provide reliable short distance communications with low power and simple antennas via high radiation angles
Simple horizontally polarized antennas only 1/8 – ¼ wavelength high (20-30 feet high on 40 meters) provide extremely effective NVIS communications

38. Critical Angle The highest radiation angle that returns a radio wave to Earth on a specific ionospheric path under specified propagation conditions
These rays, which return to
Earth, provide communications,
Unless you want to talk to E.T.

39. Skip Zone
The zone between the skip distance and surface wave range that is not easily covered without changing to a lower frequency
Tune to a DX station in QSO with a station a few hundred miles from you
The DX station may have a strong signal, but often the nearby station is weak or totally inaudible despite being much nearer to your location
You may hear the nearby station weakly via backscatter

40. Skip Distance and Skip Zone
The surface wave propagates near the surface of the Earth but quickly weakens beyond line of sight
Skip distance is measured from the transmitter to the closest point of sky wave return
The skip zone is the annulus between the end of surface wave coverage and closest point of sky wave return
No signal is received in the skip zone except via backscatter
Only a tiny part of the signal energy is backscattered into the skip zone

41. How the Sunspot Number affects High Frequency DX propagation
High sunspot numbers generally increase the probability of long distance propagation on 15, 12 and 10 meters especially from October through May Unfortunately high sunspot activity most occurs during periods of generally high solar activity when severe geomagnetic storms are much more common and much more severe

42. Trans-Equatorial Propagation - TEP
The F layer is much more intensely ionized near the geomagnetic equator during local afternoon and early evening
Stations within about 2500 miles of the geomagnetic equator can launch their signals directly into TEP propagation paths
Stations outside the TEP zone can sometimes couple onto TEP propagation via an additional single sporadic-E or F layer hop
TEP propagation refracts and travels across the equator and into the other hemisphere with no intermediary ground reflection
Stations communicating via TEP must be at approximately equal distances from the geomagnetic equator

43. Gray Line Propagation Long distance propagation between widely separated points near the daylight-darkness terminator especially on 160, 80, 40 and 30 meters

44. Near Vertical Incidence (NVIS) Propagation Typically uses low antennas only 1/8 - 1/4 wavelength high

45. Auroral Flutter
A common type of multipath fading that occurs almost exclusively on paths propagating via the auroral zone
Caused by interaction of the signal with the auroral E and F layers
Fades occur very rapidly (10 – 100 times per second) and make SSB signals sound “watery”

46. Backscatter Propagation
Due to the random nature of the ionosphere, a small amount of every signal reflected forward is reflected back. Some of these back scatter signals can be strong enough to establish communications within the skip zone. The audio quality is not perfect but depending on the signal can be quite readable. Certain antennas (low dipoles) and bands (lower bands) provide better opportunities for this propagation mode. It is also common when communicating on frequencies above the maximum usable frequency (MUF).

47. The Northern Auroral Zone during Quiet Geomagnetic Conditions

48. Auroral Backscatter
When the sun is very active, its possible to have intense auroral backscatter propagation from both the auroral F layer and the auroral E layer
The auroral-F layer MUF rarely exceeds 30 MHz
The auroral-E layer MUF can exceed 450 MHz
Backscatter communication is unique in that the stations in contact do not point their antennas at each other, but instead point at the region of intense ionization (typically +/- 45 degrees of due north for stations in the northern hemisphere)
During periods of high solar activity, the auroral zone expands southward, approaching the US-Canadian border

49. Auroral-E Backscatter Communications
During periods of intense auroral activity, the E-layer in the auroral zone can support intense backscatter of 10, 6 and 2 meter signals
Multi-path propagation with the aurora zone contributes extreme noise modulation to the backscattered signal
CW is normally used for Auroral-E backscatter communication
To work via Auroral-E, the transmitter and receiver point their antennas at the auroral zone – typically +/- 45 degrees from North -- and never at each other

50. Long distance Propagation during Periods of Low Sunspot Activity
The 20 meter band almost always supports worldwide DX propagation during daylight hours at any point in the sunspot cycle
The 80 and 40 meter bands support worldwide DX propagation from October through April
15, meters becomes less reliable for daylight DX communications during the bottom of the solar cycle
12 and 10 meters become unreliable for daylight DX communications during the bottom of the solar cycle

51. Propagation Characteristics of the HF Amateur Bands

52. 160 Meters
Primarily a nighttime regional band from September through April
Daytime operation is very ineffective compared to 80 and 40 meters
Not a popular band during summer because of frequently intense QRN caused by lightning storms within 400 miles
Night time range is reliable from NVIS ranges out to about 500 miles with a full size or loaded horizontal inverted-V dipole, about 50 feet high or more
Worldwide DX is easily achieved with a 60 foot tall inverted-L vertical with a fairly efficient radial system
Receiving antennas such as small loops, Beverages or phased arrays of short verticals are very effective and quite popular

53. 80 Meters
Primarily a nighttime regional band with reliable low power coverage out to about 1500 miles
Reliable early morning and late afternoon low power NVIS operation out to about 200 miles
Much less reliable than 40 meters from 9 a.m. to 3 p.m.
Worldwide DX is easily achieved with low power and antennas such as
a full size or loaded inverted-V horizontal dipole, 50 feet high or more
or a 35 foot tall inverted-L vertical with a reasonably efficient radial system
Not as badly impacted as 160 meters by summer lightning storm QRN

54. 60 Meters Reliable daytime short range coverage to about 400 miles
Because of the 50 watt ERP power limit, range is usually limited to about 750 miles even at night
Transcontinental and intercontinental operation is possible from October through April
Band is not available on many older rigs so activity is usually sparse

55. 40 Meters
Very reliable low power daytime regional operation from NVIS ranges out to about 400 miles
The E layer blankets the F layer during daylight hours
Worldwide DX is easily worked with low power from late afternoon through sunrise
Lots of CW and digital activity between kHz
Can be difficult to find an empty spot for SSB operation between kHz when DX conditions are good in the evening
The band above 7200 kHz is a short wave broadcast band in many parts of the world making night time operation difficult

56. 30 Meters
A good daytime band for low power communications out to about 500 miles
A good late afternoon and night time band for worldwide DXing
During low sunspot activity for the next five years, the best DXing opportunities are usually within a few hours of sunrise and sunset because the MUF drops below 10 MHz during the night in the winter months
Unlike the other HF bands, low power and simple antennas are almost universally used

57. 20 Meters The King of the DX Bands since the 1920s
Almost always supports DX propagation during daylight hours at any point in the sunspot cycle
Usually has a Skip Zone extending out to about 400 to 800 miles
Stay open until very late at night during the spring and summer
Low power with a simple dipole antenna only feet high can easily work the world

58. 17 Meters
Low power and simple antennas are much more common than on 20 meters
Opens somewhat later than 20 meters and closes earlier
The skip zone typically extends out to about 800 miles
No contesting on this band so its good for both DXing and rag-chewing during busy contest weekends

59. 15 Meters
A year round daytime worldwide DX band, but not as reliable as 20 or 17 meters for the next five years of low sunspot activity
The skip zone is commonly about 800 to 1200 miles

60. 12 Meters A combination of 15 and 10 meter characteristics
Contesting is not allowed on this band so its clear for rag-chewing and DXing even on busy contest weekends
DXing opportunities are less frequent with low sunspot activity for the next five years

61. 10 Meters Sits on the threshold of VHF
A daytime rag-chewing and DXing band
Low power with modest antennas can easily make world wide DX contacts when the band is open
The F layer skip zone often exceeds 1000 miles
Sporadic-E propagation frequently allows closer contacts during June and July
Short skip sporadic-E propagation in the 10 meter band during in June and July often indicates the possibility of 6 meter sky wave propagation

62. What bands should I use during the next five years of low solar activity?
Each band has it unique advantages and disadvantages
The most reliable worldwide daytime DX propagation will be on 20 and 17 meters and occasionally on 15 meters
The most reliable worldwide night time DX propagation will be on 40 meters
80 meters will provide excellent worldwide DX propagation at night from October through April