Radio Wave Propagation2

7/17/2019 Radio Wave Propagation2

http://slidepdf.com/reader/full/radio-wave-propagation2-568c3752b1682 1/22



The sun infuences all radio communicationbeyond ground-wave or line o sight ranges

Conditions vary with the time o day,

season, and latitude/ longitude REFLECT!" occurs at any boundary

between materials with di#erent dielectricconstants

Radio waves may be refected by buildings,trees, vehicles, the ground, water, ioni$edlayers in the outer atmos%here, or di#erentair masses having di#erent tem%eraturesand moisture content



&ome radio energy will be absorbed bythe medium it %asses through, some%asses on through the material

REFR'CT!" is the bending o a wave as it%asses through one medium into another (ending occurs because the wave is at a

di#erent s%eed in the new material 'mount o bending increases at higher

re)uencies &%eed o waves through the atmos%herechange as the tem%erature, air densityand levels o ioni$ation are di#erent

*ost +F bands de%end u%on reraction



waves were not bent



'#ects re)uencies below . mh$ .-0. miles above the earth1s surace Contains ree ions and electrons oni$ation de%ends on ultraviolet radiation

rom the sun &2i% distances de%end u%on re)uency

used, time o day, and density o theionos%here

&everal layers o varying distances atvarious heights



+F Communications 3, E, F4, F layers 3 layer 567-77 miles8 'cts as an RF s%onge

with ma9imum absor%tion during daylight

hours thus dictates the L:F E layer 507-;7 miles8 E#ective reraction

only during daylight hours F layer 5<.-7. miles 3uring daylight, there

are two layers, F4 and F F4 is not an im%ortant %ro%agation medium=

the F region is the %rimary mediumsu%%orting +F communications 5.. miles8=F4 and F combine onto one layer at night



onos%heric waves 5s2y waves8 *ain %ortion o the radiationthat leaves the antenna at angles above the hori$on

Tro%os%heric waves Radiation 2e%t close to the earth1ssurace due to bending in the lower atmos%here 5higher +F orlower >+F8

?round waves 5surace waves8 Radiation directly a#ected bythe earth1s surace- Earth-guided surace wave- >ertically %olari$ed and absorbtion increases with re)

- Travels much urther over water than over land



The medium or most all amateur radiocommunication below . mh$

The ionos%here reracts the radio wave and

returns it to earth The ma9imum usable re)uency 5*:F8 is a

unction o how highly ioni$ed the F regionis

The lowest usable re)uency 5L:F8 is aunction o obsorbtion, signal-to-noiseratio, %ower and transmission mode=Correlates with movement o the sun and%ea2s at noon



&uns%ot cycles average 4.@; years inlength

't solar ma9ima, the ionos%here isca%able o reracting radio signals u% to6. mh$ or higher

't solar minimum, reraction is reduced

and re)uencies above . mh$ becomeunreliable

Ae are currently in the downward slo%eo cycle



Electromagnetic B-rays, :ltraviolet5:>8, E9tremely :ltraviolet 5E:>8

3uring solar fares, :> and B-rayemissions increase causingincreased signal loss on +F

B-ray fares C 5smallest8, * 5medium

si$e8,B 5the largest8 in 4-D 'ngstrom

range



&!L'R FL:B is the basic indicator o solarradiation

- &olar Flu9 :nits 5&F:8 is the amount o solar

noise or fu9 that is emitted at D.. mh$ 54.@;cm8 - &F: e)uates to the levelo ioni$ation in the F layer thus is a goodindication o conditions or +F com

- &F: values run rom about 7. to as high as

.. - Low values indicate low *:F= high valuesindicate good ioni$ation to su%%ort longdistance communications at higher thannormal re)uencies



&*!!T+E3 &:"&!T ":*(ER& 5&&"8refect the level o suns%ot activity

Calculated using 0 month o data beore

and 0 months o data ater the desiredmonth the desired month

>ary rom . to .. with an average o4.. at ma9

+igh &&"s are best or +F %ro%agationLow &&"s are best or LF %ro%agation



+igh %article emissions 5%rotons andal%ha %articles8 cause higher

absor%tion in %olar regionsLow %article emissions causemagnetic Geld disturbances, auroras,and s%oradic E

&%oradic E %ro%agates 7. and 466mh$ signals



Long distance >+F communicationor stations e)uidistant rom the

geomagnetic e)uator+y%othesi$ed to be a result o anintensiGed F layer during highsuns%ot activity

&ignals have a rough aurora-li2e note



"atural variations in the geomagnetic Geldare classiGed into )uiet, unsettled, active,and geomagnetic storm levels

K index (0-9) is a )uasi-logarithmic localinde9 o -hourly range in magnetic activityrelative to an assumed )uiet-day curve or asingle geomagnetic observatory site

A index (0-400) is a daily average o the Hinde9 values

?enerally, an ' inde9 at or below 47 and aH inde9 at or below is best or %ro%agation



D. I 6. mtrs good bands or distantcommunication es%ecially during suns%otminimum

. mtrs allows greater distances than 6. mtrsat night

. mtrs most %o%ular long haul band duringall %hases o the suns%ot cycle but closes downat night during winter and suns%ot minimum

47 mtrs during suns%ot minimum ew stationsheard day or night 4. mtrs with low absor%tion allows good

communication with relatively low %owerduring daytime



'RRL %ro%agation %agehtt%//www@arrl@org/tis/ino/%ro%agation@html

"!'' %ro%agation re%orthtt%//www@sec@noaa@gov

JRK &olar Re%ort www@)r$@com Eham ro%agation www@eham@net 3B &ummit oha)@2olumbus@com/d9s/ &olar Terrestrial 'ctivity Re%ort

htt%//www@d9lc@com/solar

Radio Wave Propagation2

Documents

Transcript of Radio Wave Propagation2