HF Propagation An Introduction By Gary Sutcliffe, W9XT Revised August 2018 Copyright (c) 2006-2018 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

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 W9XT

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 W9XT

The High Frequency Bands HF ranges from 3-30 MHz Traditional Bands WARC Bands *Technically MF 30M 10.10-10.15 MHz 17M 18.068-18.168 MHz 12M 24.890-24.990 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 W9XT

What Makes Long Distance HF Communications Work? W9XT

The Ionosphere makes HF exciting Upper altitudes ~30-620 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 W9XT

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 W9XT

Ionosphere Layers There are different layers of interest to radio operators, labelled D, E & F W9XT

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 W9XT

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 W9XT

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 W9XT

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 W9XT

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 W9XT

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 W9XT

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 1645-1715 Low period around 1800 was the Dalton Minimum Source: http://spaceweatherlive.com 8/8/2018 W9XT

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. W9XT

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 W9XT

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 W9XT

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 W9XT

Paths Radio Wave Follow More or less follow great circle path Long path – the long way around the world Most common on 40 - 15 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 W9XT

Band by Band Characteristics W9XT

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’ W9XT

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 W9XT

40 Meters (7.0-7.3 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 W9XT

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30 Meters 10.10-10.15 MHz Note limitations No phone, 200 Watts Day- 1000 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, 200 Watts W9XT

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 W9XT

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 W9XT

15 Meters (21.0-21.45 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 W9XT

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 W9XT

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 W9XT

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 W9XT

Where are We in the Sunspot Cycle? Summer 2018 W9XT

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: http://spaceweatherlive.com 8/8/2018 W9XT

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 W9XT

Band Summary for 2018-2019 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 - W9XT

Learning Propagation W9XT

Learning Propagation Get on the air! NCDXF Beacons Get on different bands at different times NCDXF Beacons http://www.ncdxf.org/beacons.html 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 W9XT

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 http://wspr.net to see map of who is hearing who Maps of who is hearing who Database of nearly 1 billion spots available W9XT

WSPR Maps Screen shots from http://wsprnet.org Conditions were poor at this time. 20M, Everyone selected 20M, stations heard by W9XT selected W9XT

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 W9XT

“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 www.w9xt.com W9XT