UNDERSTANDING RF PROPAGATION - W7AIA
UNDERSTANDING RFPROPAGATIONBY TIM KUHLMAN, PEKD7RUS
RF PROPAGATION WHAT IS RF PROPAGATION? WHAT ARE THE DIFFERENT TYPES OF PROPAGATION? HOW DOES OUR ENVIRONMENT AFFECTPROPAGATION? HOW TO PREDICT PROPAGATION WHAT ARE RADIO SIGNALS AND HOW THEY REACT?
WHAT IS RF PROPAGATION? IT IS THE MEANS IN WHICH RADIO SIGNALS TRAVEL. RADIO SIGNALS ARE ELECTROMAGNETIC WAVES. THEY WERESTUDIED AND QUANTIFIED MY JAMES MAXWELL IN A SET OFEQUATIONS NAMED AFTER HIM.
WHAT IS RF PROPAGATION? EXPERIMENTS RELATING TO THE WORK OF MAXWELL WERE PERFORMEDBY HEINRICH HERTZ. THE RESEARCH OF BOTH MEN, AND OTHER SCIENTIST SHOWED ARELATIONSHIP BETWEEN THE ELECTRIC FIELD AND MAGNETIC FIELD OF ARADIO WAVE AS IT TRAVELS. AS A WAVE TRAVELS, IT WANTS TO TRAVEL IN A STRAIGHT LINE AND WILLBE: CONDUCTED ATTENUATED (ABSORBED, SCATTERED) REFLECTED REFRACTED
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TRAVELING SIGNALS - BASICReflected Wave - TrPropagatingWave - TpSource Transmitted Wave TsIdeal Material
TRAVELING SIGNALS - BASICReflected Wave - TrSource Transmitted Wave TsIdeal MaterialPropagatingWave - Tp
TRAVELING SIGNALS - BASICTs Tr Tp TaorTp Ts – Tr-TaorTr Ts – Tp -TaReflected Wave - TrPropagatingWave - TpSource Transmitted Wave TsNon-Ideal Material(such as glass)Some of thesource wave isabsorbed - Ta
TRAVELING SIGNALS – WITH REFRACTIONReflected Wave - TrPropagatingWave - TpSource Transmitted Wave TsSome of thesource wave isabsorbed - TaSome Material orspace .
TRAVELING SIGNALS - BASICPropagatingWave - TpSome of thesource wave isabsorbed - TaSome Material(Ionosphere)Reflected Wave(Refracted) - TrSource Transmitted Wave Ts
TRAVELING SIGNALS - BASICPropagating Wave –Refracting through theatmosphere - TpSome of thesource wave isabsorbed - TaSome Material(Ionosphere)Reflected (Refracted)Wave - TrSource Transmitted Wave Ts
MORE ON REFRACTION
MORE ON REFRACTION
MODES OF RADIO SIGNAL TRAVEL. FREE SPACE – THIS IS THE IDEAL MODE OF WAVE PROPAGATION. THERE IS NOTHINGTO GET IN THE WAY OR TO INTERACT WITH THE SIGNAL. IN REALITY,THIS RARELY EVER OCCURS. THE BEST ENVIRONMENT TO TEST THIS IS IN OUTER SPACE, OUTSIDEOUR SOLAR SYSTEM. ON EARTH, IN AN ANECHOIC CHAMBER. FREE SPACE AND OPEN SPACE ARE FORMS OF “DIRECT WAVE”PROPAGATION.
MODES OF RADIO SIGNAL TRAVEL. OPEN SPACE SIMILAR TO FREE SPACE EXCEPT THERE ARE OBSTACLES SUCH AS BUILDINGS,TREES, HILLS, PEOPLE . BUILDINGS AND HILLS CAN CAUSE SIGNALS TO BE REFLECTED OR ABSORBEDDEPENDING ON THE FREQUENCY. A PHENOMENON CALLED KNIFE EDGEREFRACTION CAN DIFFRACT A SIGNAL AROUND A CORNER. TREES, HILLS AND PEOPLE CAN ABSORB SIGNALS. THESE PROPERTIES ARE MOST LIKELY TO BE OBSERVED AT VHF FREQUENCIES(50 MHZ) AND HIGHER. REFLECTED SIGNALS CAN CAUSE A RECEIVER TO SEE MULTIPLE SIGNALS OFTHE SAME TRANSMISSION (MULTIPATH).
MODES OF RADIO SIGNAL TRAVEL. OPEN SPACEFrom ARRL Amateur Radio Education and Technology Program
MODES OF RADIO SIGNAL TRAVEL. GROUND WAVE GROUND WAVE PROPAGATION OCCURS AT LOW FREQUENCIES. TYPICALLY 4MHZ AND BELOW. (THINK 80M, 160M BANDS AND AM BROADCAST). IN GROUND WAVE PROPAGATION, THE MAGNETIC FIELD OF THE RF SIGNALCOUPLES WITH THE EARTH. A VERTICALLY POLARIZED ANTENNA WORKSWELL FOR THIS TYPE OF PROPAGATION. OFTEN GROUND WAVE PROPAGATION IS CONFUSED FOR OPEN SPACE(DIRECT WAVE) PROPAGATION.
MODES OF RADIO SIGNAL TRAVEL. SKY WAVE RADIO SIGNALS ARE REFRACTED OR REFLECTED OFF OF THE EARTHS UPPERATMOSPHERE – THE IONOSPHERE. BY BOUNCING A SIGNAL OFF THE IONOSPHERE, RADIO SIGNALS CANTRAVEL GREAT DISTANCES. THE SUNS RADIATION ACTS DIRECTLY ON THE ATMOSPHERE TO IONIZE GASPARTICLES. THE HIGHER THE IONIZATION, THE MORE RADIO SIGNAL REFLECTION. THE SUNS AFFECT ON THE ATMOSPHERE CHANGES BASED ON THE TIME OFDAY AND THE SOLAR ACTIVITY AS INDICATED BY THE SUN SPOTS.
SKY WAVE & REFRACTION
SKY WAVE & REFRACTION
THE ATMOSPHEREF1 and F2 Layers combine at nightto form 1 layer.D Layer exists during theday.From Radio Electronics.com
THE ATMOSPHEREFrom the G7LRR Web Page
THE ATMOSPHEREFrom the G7LRR Web Page
SKY WAVES AS THE CHARGED PARTICLES OF THE IONOSPHERE INCREASES, THEAMOUNT OF RF REFLECTION (REFRACTION) ALSO INCREASES. THIS IS CALLED THE CRITICAL FREQUENCY AND IS MEASURED BYLOOKING AT THE HIGHEST FREQUENCY THAT CAN BOUNCE OFF THEATMOSPHERE.
CRITICAL FREQUENCYIonosphere7 MHzCritical Freq is the maxFreq that will bereflected – 7 MHZ14 MHz
SKY WAVES THE CRITICAL FREQUENCY IS MEASURED WITH A VERTICAL SIGNAL, ASIGNAL POINT STRAIGHT UP. (THINK NVIS ANTENNA.) THE UPPER LIMIT OF FREQUENCY THAT CAN BE REFLECTED CAN BEINCREASED BY CHANGING THE ANGLE THAT IT HITS THE IONOSPHERE. (SNELL’S LAW) THE SHARPER THE ANGLE, THE HIGHER THE FREQUENCY UNTIL THEMAXIMUM USEABLE FREQUENCY (MUF) IS ACHIEVED.
MAXIMUM USABLE FREQUENCY (MUF)Ionosphere7 MHz28 MHZ14 MHz
MUF MAP – WWW.SPACEW.COM/WWW/REALTIME.PHP
PREDICTING PROPAGATION FOLLOW THE RULES OF THE PROPAGATION SUMMARY. HIGHER FREQUENCIES DURING THE DAY, 14MHZ – 29 MHZ. LOWER FREQUENCIES AT NIGHT. 1.6MHZ TO 14 MHZ DURING THE SOLAR MINIMUM, POOR PROPAGATION ON 10 MHZ ANDHIGHER, GOOD LOW FREQUENCY AT NIGHT DUE TO LESS ATMOSPHERICNOISE. DURING THE SOLAR MAXIMUM, GOOD PROPAGATION ON 14 MHZ ANDHIGHER EVEN INTO THE EVENING. POOR LOW FREQUENCY DUE TO HIGHERATMOSPHERIC NOISE.
PREDICTING PROPAGATION MUF FORECAST MONITOR THE SOLAR INDEX HTTP://WWW.WM7D.NET/HAMRADIO/SOLAR/INDEX.SHTML HTTP://WWW.ANZADX.NET/ WWW.ARRL.ORG K7RA SOLAR UPDATE SOLAR FLUX INDEX OF 70 IS LOW POOR DX SOLAR FLUX OF 110 IS MODERATE GOOD DX SOLAR FLUX OF 150 IS HIGH GREAT DX LISTEN TO HF BANDS LISTEN TO WWV POOR DX DOES NOT MEAN NO DX. WEAK SIGNAL MODES CANPROVIDE A LOT OF DX FUN.
PREDICTING PROPAGATION LISTEN TO BEACONS SUCH AS HTTP://WWW.NCDXF.ORG/BEACON/BEACONSCHEDULE.HTML
PREDICTING PROPAGATION SPOTTING NETWORKS - HTTP://WWW.DXSCAPE.COM
PREDICTING PROPAGATIONSFI – Solar Flux IndexA IndexK IndexSignal Noise LevelGeomagnetic Field
PREDICTING PROPAGATION
ATMOSPHERIC DISTURBANCE
ATMOSPHERIC DISTURBANCE
THE STRANGE KNIFE EDGEDIFFRACTION FRESNEL ZONEImage from ualberta.caImage from broadbandbuyer.com
THEUNPREDICTABLE SPORADIC E AFFECTS FREQUENCIES 28 MHZ TO 222 MHZ MAY BE INTENSE FOR SHORT PERIODS OFTEN MORE FREQUENT DURING THE SOLARMINIMUM TROPOSPHERIC DUCTING CAN OCCUR FROM CHANGES IN TEMPERATURE,HUMIDITY AND PRESSURE. OCCURS WHEN REFRACTION IS SO GREATRADIO WAVES ARE BENT BACK TO THE SURFACE. MAGNETOSPHERIC DUCTING A STRANGE PHENOMENON WHERE RADIOSIGNALS ARE BELIEVE TO FOLLOW THE EARTHSMAGNETIC FIELD LINES.
THE END REFER TO THE ARRL HANDBOOK CHAPTER 21 FOR MORE INFORMATIONON PROPAGATION. REFER TO “RADIO PROPAGATION PRINCIPLES AND PRACTICE” BY IANPOOLE, G3YWX QUESTIONS? TIM KUHLMAN, KD7RUS KD7RUS@ARRL.NET
ground wave ground wave propagation occurs at low frequencies. typically 4 mhz and below. (think 80m, 160m bands and am broadcast). in ground wave propagation, the magnetic field of the rf signal couples with the earth. a vertically polarized antenna works well for this type of propagation.
on radio propagation. This handbook also provides basic information about the entire telecommunications environment on and around Mars for propagation researchers, system . 1.2 Radio Wave Propagation Parameters. 4 2. Martian Ionosphere and Its Effects on Propagation (Plasma and Magnetic Field). 7
1 How Plant Propagation Evolved in Human Society 2 2 Biology of Plant Propagation 14 3 The Propagation Environment 49. part two. Seed Propagation. 4 Seed Development 110 5 Principles and Practices of Seed Selection 140 6 Techniques of Seed Production and Handling 162 7 Principles of Propagati
wave propagation, including ground wave and ionospheric propagation, goes on to make this text a useful and self-contained reference on antennas and radio wave propagation. While a rigorous analysis of an antenna is highly mathematical, often a simplified analysis is sufficient for understanding the basic principles of operation of an antenna.
Ground Wave Propagation Follows contour of the earth Can Propagate considerable distances Frequencies up to 2 MHz Example oAM radio. Sky Wave Propagation. Sky Wave Propagation Signal reflected from ionized layer of atmosphere back down to earth Signal can travel a number of hops, back and
Ground Wave Ground wave propagation occurs at low frequencies. Typically 4 MHz and below. In ground wave propagation, the magnetic field ofIn ground wave propagation, the magnetic field of the RF signal couples with the earth. A vertically polarized antenna works well for this type of propagation.
Overview of HF Propagation Characteristics of HF radio propagation – Propagation is possible over thousands of miles. – It is highly variable. It has daily and seasonal variation, as well as a much longer 11 year cycle. HF radio waves may travel by any of the following modes: – Ground Wave – Direct
tissue culture. This resulted in the books Plant Culture Media, Vols. 1 and 2 (1987), and Plant Propagation by Tissue Culture. The latter work was first published in 1984 and then extensively revised and extended to two volumes in 1993 and 1996. The present book is based on the first volume of the 2nd edition of Plant Propagation by Tissue .
graduation, positioning them for college and careers. The grade level ELA standards begin in the Prekindergarten and Elementary ELA Standards section. Please see the introduction for more about how the anchor standards and grade level standards connect. New York State Education Department ENGLISH LANGUAGE ARTS LEARNING STANDARDS (2017) 4 NEW YORK STATE EDUCATION DEPARTMENT Reading Anchor .
