1. HF Propagation An Introduction By Gary Sutcliffe, W9XT Revised August 2018
Copyright (c) Gary C. Sutcliffe
This presentation was originally presented in 2006 when HF operating permission was given to all US hams. It was updated several times, most recently in 2015.
This presentation may be used or adapted for non-commercial use.
Ask for show of hands: How many new or never been on HF?
HF stands for High Frequency – often referred to as Short Wave
Much of the Mystique & Traditions of Ham Radio due to HF
Always surprises on HF – you never know who will come back
Like Poker – Learn in a few minutes, life time to master

2. Topics to be Covered What are the HF Bands? How HF Propagation works
Band by Band Overview
Where we are in the sunspot cycle
How can I learn more?
These are the topics to be covered in this presentation
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3. Amateur Bands A range of frequencies.
Different modes allowed on different frequency ranges of the band
Usually referred to by wavelength i.e. “40 Meters”
Historical – in early days of radio wavelengths were used to designate frequency
Wave length = 300/frequency in MHz
Band Names only approximate Wave lengths
40 Meters: 300/7 = 42.9 Meters
15 Meters: 300/21 = 14.3 Meters
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4. The High Frequency Bands HF ranges from 3-30 MHz Traditional Bands WARC Bands
*Technically MF
30M MHz
17M MHz
12M MHz
Traditional bands only on radios older than mid 1970s
The WARC bands were opened up to ham use in the late 1970s.
160M technically Medium Frequency, HF covers 3-30MHz
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5. What Makes Long Distance HF Communications Work?
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6. The Ionosphere makes HF exciting
Upper altitudes ~ miles (ISS is ~220 miles)
An ion is an atom with a charge
Caused when UV light knocks electrons off molecules
Ionization varies with
Solar activity – 11 year sun spot cycle
number of sunspots
10.7 cm solar flux‏
Sunspots and solar flux are a marker for UV levels
Season
Time of day
Intensifies during day from UV light from sun. Electrons re-combine at night.
Dissipates during darkness, but lasts longer when high levels during the day
Sunspots and solar flux are a good proxy for the amount of UV being produced
Sunspots discovered in 1611 – long history available
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7. HF Propagation Via the Ionosphere
Radio waves can propagate longer than line of sight by bouncing off ionosphere
Technically the wave is refracted, not reflected off ionosphere
At any given time there will be a Maximum Usable Freq.
- above MUF the signals may be refracted, but not enough and go out into space
Signals below MUF are returned to earth.
Return signal may bounce off earth allowing multiple hops
Lower take off angle will give longer distance per bounce.
Lower angles support higher frequencies.
At a given angle below the MUF, lower frequencies will be refracted more and return to earth at shorter distance
MUF – Maximum Usable Frequency
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8. Ionosphere Layers
There are different layers of interest to radio operators, labelled D, E & F
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9. D Layer – Lowest Layer Effects easy to see on AM Broadcast band
Caused by UV light & X-rays
Forms during the day
Disappears at night
Absorbs lower frequency signals (<10 MHz most affected)
Reason for hearing only local AM broadcast stations during the day
Effects strongest on frequencies below about 10MHz.
Effects easy to see on AM Broadcast band
Local in day
long distance night
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10. E Layer – Middle Layer Second peak Dec-Jan
Often occurs as Sporadic E (Es)
Thought to be caused by wind shear
Not usually intense enough to be noticed
Can last minutes to hours
Most common May-July
Can be very intense
Usually effective 50 MHz (6 Meters)‏ and below
Rare at 144 MHz (2 Meters) and above
Second peak Dec-Jan
Often responsible for higher bands open at night – FD is a good example
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11. Sporadic E (Es)‏ Normally the E layer is not present. Lots of fun
Can happen any time
Most common May-July
Secondary peak period Dec-Jan
Most apparent on 10 Meters and up but happens on 20 & 15
Up to ~1500 miles, multi-hop possible
Openings can be very localized or wide spread
Can result in very strong signals
Normally the E layer is not present.
Lots of fun
Often on 20 and 15, but often not recognized because F layer often occurs
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12. F Layer – Highest Layer Responsible for most HF propagation
Caused by UV light from sun
Forms during day, dissipates at night
MUF varies with ionization level
Usually splits into F1 and F2 during the day
F2 is the one most useful to hams
F Layer is the one of most interest to HF operators and especially DXers
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13. Ionization and the Sun
Ionization level corresponds closely to sun spots
Sunspots do not cause ionization, UV light does
Sunspots are a good indication of UV levels
Sun spots follow an 11 year cycle
Sun spots
range from 0 to ~ 150
Smoothed number used (average +/- 6 months)
Solar flux – 10.7 cm radiation
Another marker for UV levels
Ranges from ~60 to ~250
Ionosphere postulated 1839, proven 1925
Sunspots and solar flux closely related – rise and fall together
UV light was not discovered until 1801
Sunspots discovered in 1611
Radio waves discovered 1870’s
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14. Photo by Hans Bernhard - Creative Commons Attribution
Sunspots
A time with a lot of sunspots.
The sun rotates in a 24.5 day period at equator
It is slower are high latitudes.
NASA has two spacecraft monitoring the other side of the sun, so we now
When new sunspots will rotate into view.
Photo by Hans Bernhard - Creative Commons Attribution
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15. Sunspot Cycles Source: http://spaceweatherlive.com 8/8/2018 W9XT
Note we have to go back 100 years to find a peak as low as current cycle.
Maunder Minimum
Low period around 1800 was the Dalton Minimum
Source: 8/8/2018
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16. Geomagnetic Field Disrupted by charged particles from the sun
Indices rate stability of magnetic field of Earth
Reported as A & K indices
K single site
A Planetary index
Low index = stable / high index = unstable
Charged particles from sun cause high A & K
Geomagnetic storm
Often result in auroras
Absorption of radio waves on polar paths
The earth is a big magnet
There is a magnetic field around the earth. It traps charged particles. Propagation is best when it is quiet. Propagation is worst when it is disturbed and really bad during geomagnetic storms.
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17. Solar Flares, CMEs, SIDs Coronal Mass Ejection Solar Flares
Charged particles ejected into space
Often associated with solar flares but there are other causes
Solar Flares
X-ray burst can cause HF radio black out (Sudden Ionospheric Disturbance)
X-rays cause dense D-layer ionization
HF absorption, VLF enhancement
Charged particles released
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18. The Auroral Zone Size changes based on geomagnetic activity
Can have an aurora if it get large enough to get to our latitude
Absorbs and/or distorts HF signals going through it
The auroral zones are doughnut shaped centered on geomagnetic poles
Size depends on auroral activity.
Signals going through the auroral zone absorbed
Often possible from Midwest to hear southern Europe (Italy, Spain, etc.), but not northern (Sweden, Norway, etc.) during high geomagnetic periods
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19. Propagation Numbers Sources High SF (solar flux) means higher MUF
WWV 18 minutes after the hour
Various Internet sites
High SF (solar flux) means higher MUF
Need high numbers for 10 & 15 Meters to open
Lower levels best for 160 & 80 Meter DXing
Low A & K mean Geo-magnetic field stability
Low needed for polar paths (mid-west USA to Northern Europe, Japan)
North-South paths not affected as much by geomagnetic field
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20. Paths Radio Wave Follow
More or less follow great circle path
Long path – the long way around the world
Most common on Meters
Back Scatter – no direct path open
Signals scatter off area with common propagation
Grey Line
Low frequency signals follow terminator
Sunrise or sunset at each end
Great circle – shortest path: put pins in a globe for two points and put string between them. That is the Great Circle path
Long Path – Evening or Morning
Back Scatter – example: US and Europe are open to Africa, but not each other. Sometimes it is possible for US and Europe to communicate by both station pointing beams to Africa or South America.
Grey Line – Area after sunset and before sunrise that is in twilight. Often produces long distance propagation on Low bands
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21. Band by Band Characteristics
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22. 160M (1.8-2.0 MHz) Day – Absorb by D layer
Day – Local to a few hundred miles
Night – Long distances possible
Often noisy (thunder storm static)‏
A very challenging DX band
Antennas difficult because of size – Dipole ~260'
Technician: No operation permitted
Day – Absorb by D layer
Best at night during winter – less static
A 160M dipole at 50’ is like a 10M dipole at 3’
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23. 80 Meters (3.5-4.0 MHz) Day – Absorbed by D layer
Day – Local to several hundred miles
Night – World wide possible
Often noisy (lightning static)‏ - especially in the summer
Challenging DX band
Phone band sometimes called 75 Meters
Popular band for nets
Antennas difficult in small lot
Dipole ~ 133’
Big band difficult to cover with one antenna
Technician: CW (Phone & data privileges proposed)
Day – Absorbed by D layer
Best at night during winter – less static
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24. 40 Meters ( MHz)
Day – Local to 1000 miles or more
Night – World wide possible
A reliable band – almost always open somewhere
Antennas manageable
Dipole ~ 66'
Verticals with good radials effective DX antenna
Beams large but manageable with heavy duty rotor
Technician: CW (Phone & data privileges proposed)
Would pick 40M if I could only operate one band
Good mix of long & short propagation
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25. W9XT

26. 30 Meters 10.10-10.15 MHz Note limitations No phone, 200 Watts
Day miles or more
Night - World wide possible
Similar to 40M
Antennas manageable
Dipole ~46'
Vertical very effective DX antenna
WARC Band, CW & Data only, 200W max
No contesting
Technician: No operation permitted
Note limitations
No phone, Watts
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27. 20 Meters (14.0-14.35 MHz) Tough band – lots of competition
Day – 500 miles to world wide
Night -World wide possible
Considered by some as best DX band
Lots of competition
Antennas manageable
Dipole - ~33'
Beams common
Technician: No operation permitted
Tough band – lots of competition
Often the only DX band open in low sunspot periods
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28. 17 Meters (18.068-18.168MHz) Good for starting DXers
Day - hundreds of miles to world wide
Night – open world wide with high sunspot levels
Good band for beginning DXer
Antennas
Dipole ~ 25'
Beams manageable
WARC Band
No contesting
Technician: No operation permitted
Good for starting DXers
Competition is not as bad as other bands
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29. 15 Meters ( MHz)
Day – Hundreds of miles to world wide
Night – Stays open late with high sunspot levels
Great DX band in moderate-high sunspot years
Antennas
Dipole ~22'
Beams common
Technician: CW (Phone & data privileges proposed)
Worth checking even during low sunspot periods
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30. 12 Meters (24.89-24.99 MHz) Day - Hundreds of miles to world wide
Night – open only in high sunspot years
Great DX band in high sunspot years
Antennas
Dipole ~18'
Beams helpful
WARC Band
No contesting
Technician: No operation permitted
May not open during low sun spot periods
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31. 10 Meters (28.0-29.7 MHz) My favorite band
Day - Hundreds of miles to world wide
Night – open several hours in high sunspot years
Excellent DX band in high sunspot years
Very quiet
Modest stations effective
Very large band– stations can spread out to avoid QRM
Fun band for Es in late spring / early summer
Antennas
Dipole ~18'
Beams common
My favorite band
Occasional short openings to South America during sunspot minimums
World wide openings during high sunspot periods
Solar flux needs to be higher than 100 for QSOs from Midwest to Europe
Lots of Es openings in spring and some in December
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32. 10 Meters (continued)
Many propagation modes
F (with moderate to high sunspot levels)‏ Es
Aurora
Technician: CW, data, phone
Lots of different propagation modes occur on this band.
Aurora –Northern Lights. Point beam north.
SSB signals sound like Donald Duck
CW signals have buzz sound
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33. Where are We in the Sunspot Cycle?
Summer 2018
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34. Where Are We Now? Summer 2018
Notice each maximum is lower that the previous one
We could be near bottom.
One Russian report says we are at it, but next peak will be worse than last one.
Key will be how long the minimum gets and lasts. Longer minimums tend to indicate lower maximums.
Source: 8/8/2018
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35. End of Cycle 24 We are probably ~18 months from minimum
Won’t know until at least 6 months after
Expect a very low minimum like the last one
Length of minimum is a good indicator of how high the next peak will be
Look for high latitude sunspots – those are Cycle 25 spots
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36. Band Summary for
160 & 80 – Now is time to take advantage of them
40 & 30 Good DX band hours around sunset and sunrise
20 – Probably the most active DX band. Closes early
17 – Good for DX during day, especially if we get a pop in the SF
15 – Infrequent openings. South paths mostly, in middle of day. Southern Europe fall/winter possible
12 & 10 – Very infrequent openings to south during middle of the day
HF bands are typically not as good during the summer
More absorption on high bands
Shorter nights reduce openings on lower bands
Higher static levels on lower bands -
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37. Learning Propagation
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38. Learning Propagation Get on the air! NCDXF Beacons
Get on different bands at different times
NCDXF Beacons
Worldwide beacons on 20, 17,15, 12 & 10 meters
Two minute cycle time, 10 seconds per station
CW ID 100W, 1 sec tones: 100W, 10W, 1W and .1W
Propagation Prediction Programs
W6EL
ITS HF Prop
The only way to learn propagation is to get on the air.
Beacons are great because there is not always someone on the air from open areas
NCDXF beacons operate in time slots. Even if you can’t copy the CW ID, you can tell which station by the time
Propagation programs can be instructional
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39. WSPR – Weak Signal Propagation Reporter
World wide beacon network – You can be a beacon!
All bands
To get on
Download WSJT software (free)
Interface radio to PC
See what stations you can hear
Log on to see map of who is hearing who
Maps of who is hearing who
Database of nearly 1 billion spots available
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40. WSPR Maps Screen shots from http://wsprnet.org
Conditions were poor at this time.
20M, Everyone selected
20M, stations heard by W9XT selected
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41. On the Air Learning
Operating activities that help learn propagation
Work on awards
Worked All States
DXCC – work 100 countries
Contests
The increased activity gives a good indication of band openings
Call CQ on a dead band – you might be surprised what comes back!
Predicting propagation is like predicting the weather. There will always be surprises!
At lot time the band is open but nobody is transmitting!
Opening in predictions are based on percentage of days it will open – sort of like chance for rain
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42. “Takes five minutes to learn, a lifetime to master”*
Summary
HF provides a life time of challenges and fun
Opens the whole world
“Takes five minutes to learn, a lifetime to master”*
*With apologies to Mike Sexton of the World Poker Tour
This presentation will be available at
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