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THE AMATEURS FRIEND OR Enemy A short course on Propagation - - PowerPoint PPT Presentation
THE AMATEURS FRIEND OR Enemy A short course on Propagation - - PowerPoint PPT Presentation
PROPAGATION THE AMATEURS FRIEND OR Enemy A short course on Propagation Propagation What is it? What causes it? How does it effect HF Communications How do we understand the charts Were do we find the propagation information What is it?
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A short course on Propagation
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Propagation
What is it? What causes it? How does it effect HF Communications How do we understand the charts Were do we find the propagation information
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What is it? It is the means of transmitting a signal from Point A to B Three types of propagation: Direct Wave Ground Wave Sky Wave
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Direct Wave is line of sight from point A to B Think HT to Repeater Ground Wave follows the curvature of the earth and is the propagation method for low frequencies including broadcast band to upper limit of about 2 MHz Sky Wave refracted wave from the ionosphere
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For this presentation we will be discussing Sky Wave only
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Ionospheric Propagation
Ionization in the ionosphere is caused mainly by radiation from the Sun. However it is not the ion that causes radio signals to be refracted but the free electron produced when an atom is ionized. The more free electrons per meter squared the better the refraction. What kind of radiation from the sun causes this ionization? Mostly it’s ultraviolet light and X-rays.
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The ionosphere consists of a number of refractive and absorptive layers including the D, E, F1 & F2 layers.
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Fou
- ur impo
mportant rtant def efini nitions tions we we nee need to to und under erstand stand Cri
ritical tical Fre requency: quency: T The e highe ghest t fr frequency quency that at will ll be re refle flected cted To ear arth h when en the e tra ransmitted smitted sign gnal al is stra raight ght up 9 90 degr grees. ees. Max aximu mum m useable able Fre requenc quency y M MUF: : T The he highe ghest st fr frequency quency t that at can an be used d to communic mmunicate ate betwee tween n point int A a A and B. . R Rule ule of f thumb umb is that at this is is 3X t the e cri ritica tical l fr frequency quency fo for r the e F lay F layer r an and ab about ut 5X X fo for r the E la laye yer. r. The e Lo Lowes west t Useable able Fre requenc quency y LU LUF: : T The e lowest west fr freque equency ncy
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Op Opti timum mum wo working king fr frequ quenc ency: y: The he best t fr frequency uency fo for com
- mmunica
munications tions betw tween en Poi
- int
nt A & B A & B. By rul ule e of
- f thu
thumb mb to to be e about
- ut
20% % below
- w MU
MUF.
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The Wave front t le leaves es the anten enna na as a lin linear r wave eit ither er horiz izonta ntal l or v vertic ical ally ly pola lariz ized ed. . When it it re reaches es the io ionosph pher ere e it it b breaks ks in into two cir ircula lar pola lariz ized d waves. s. The main in wave is is rig ight cir ircula lar and known n as the ordin inar ary y wave “O”. The second nd wave e is is le left cir ircula lar and known n at th the extra a ordin inary ry wave “X”. These e two waves es have e sli lightly ly dif iffer feren ent t propaga gation tion character teris istics tics.
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75/80 meters is the band most used for NVIS
- peration.
WHY Since this is a 90 degree vertical signal one must operate within the critical frequency window. The critical frequency seldom gets as low as 160 meters or as high as 40 meters except at solar cycle maximum. Therefore: The 160M and 75/80m bands are best for NVIS operation.
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SUN IN 2012
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THE SUN AT THE PRESENT—NO SPOTS
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DATA WE NEED TO KNOW
Solar Flux “SFI”: Measure of solar radiation at 10.7 cm. Higher the better Seldom below 68. Sun Spot Number “SN”: Higher the better. Solar Wind “Kps”: Lower the better. foE: Critical frequency of E layer Fof2: Critical frequency of F layer MUF: Maximum useable frequency K index: Geomagnetic field measurement taken every 3
- hours. Lower the better.
A index: average of 8 previous K index.
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WHERE DO WE GET IT?
http://Solarham.com Excellent source of most of the indices. http://surf.colorado.edu/login.dcc Source of ionograms - Need permission to use but not hard to get. Initial page will have the current ionogram. https://www.hfunderground.com/propagation/ Lots of info https://www.swpc.noaa.gov/ Likewise https://www.qrzcq.com/dxcluster World wide DX cluster http://www.wm7d.net/hamradio/solar/ http://www.hamqsl.com/solar.html
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WHAT IS THE BEST STUDY GUIDE ON PROPAGATION? Propagation and Radio Science From the ARRL Bookstore
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