Propagacion HF.docx

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HF Propagation

1 HF Propagation

HF radio signals (2-30MHz) can propagate from one location to another via ground wave (line ofsight) and via the ionosphere.

1.1 Frequency and angle of radiation

Figure 1 Frequency and angle of radiation

nerg! is radiated from the antenna in an envelope. "he shape of this envelope is dependent onthe design of the antenna and the fre#uenc! $eing transmitted.

"here are three portions of this radiation that are useful for communications. "hese useful portions

are distinguished $! the angle the! radiate from the antenna. %n the a$ove diagram the! arerepresented $! the gre! shaded triangles la$elled &'% *!wave +round , irect wave.

&ote that the $lue portions of radiation in Figure represent angles at which the radiation either

passes through the ionosphere or is totall! a$sor$ed $! the ionosphere. Q-MAC Electronics Pty Ltd Q-

MAC Electronics Pty Ltd Page 4 of 7 HEAD OFFICE 142 Hasler Road, Osborne Park WA 6017.

Australia Tele!one" #61$ %242 2%00, &a'si(ile" #61$ %242 )%00 *(ail" info+(a'.'o( Web"---.(a'.'o(

Figure Figure

1.2 Ground / Direct Wave

+round wave communications are possi$le over relativel! short distances. "he effective distanceachieva$le depends primaril! on the conductivit! of the terrain over which the signal passes. %ne/tremel! dr! conditions the signal ma! onl! travel a few *ilometres over water the signal ma!travel 001s of *ilometres.

"!pical ranges for different terrains

esert 4*m

Moist farmland 30*m

eawater 00*m

ense tropical 5ungle will also dramaticall! attenuate (limit) the range of a ground wave.

6ower fre#uencies will provide the $est range overall. 7ut the noise floor on fre#uencies less than 3to 8MHz is t!picall! too great to $e useful especiall! during the da!.

"he optimum fre#uenc! range for ground wave is 8 9 : MHz.

ou$ling the output power on a ground wave signal will improve effective range $! less than 2;. "odou$le the range of a ground wave signal re#uires an increase in output power $! a factor of <=



1.3 Skyave

>ropagation via the ionosphere is *nown as s*!wave propagation. "his is the portion that is mostcommonl! perceived as providing good long range communications.

%n general as fre#uenc! is increased the angle (? in ) of the radiated envelope to the horizon

$ecomes smaller (radiation is focussed more horizontall!). "herefore an increase in fre#uenc!leads to an increase in distance for a s*!wave (ref. ). "he distance at which a s*!wave returns toearth is called the hop or !kip di!tance and the area in $etween is called the !kip "one.

"he state of the ionosphere is constantl! changing primaril! due to the dail! c!cle of da! and night. @t night the s*!wave also returns to earth at a greater distance $ecause it is refracted from a

higher la!er in the ionosphere. Q-MAC Electronics Pty Ltd Q-MAC Electronics Pty Ltd Page of 7

HEAD OFFICE 142 Hasler Road, Osborne Park WA 6017. Australia Tele!one" #61$ %242 2%00, &a'si(ile"#61$ %242 )%00 *(ail" info+(a'.'o( Web" ---.(a'.'o(



Figure

Figure 2 The eect of changing ionospheric layers

"he same fre#uenc! will $e refracted at a higher la!er in the ionosphere during the night and willreturn to earth at a greater distance than it would during the da!.

Asing s*!wave propagation it is possi$le to achieve t!picall! 00 9 :00*m range.

"he effective range of s*!wave propagation is primaril! dependent onB @ntenna !stemB Fre#uenc!B "ime of a!

Cptimum fre#uenc! range is 3 9 4MHz.

1.# $%&S ' $ear %ertical &ncident Skyave

"he third portion of antenna radiation that is useful for communications leaves the antenna at anear-vertical angle (ref. ) and is reflected $ac* to the earth and providing good communicationsfrom 0 to :00*m.

&'% is e/ceptionall! effective $ecause it eliminates the s*ip zone and provides continuouscoverage from the transmitter out to appro/imatel! :00*m. %t is ideall! suited to regions , terrains ofhigh attenuation (e.g dense forests mountains etc).

ffective &'% propagation is primaril! dependent on the design of the antenna s!stem $eing usedand choosing the correct fre#uenc! for the time of da!.

Fre#uencies that provide good &'% coverage are

8 9 : MHz during the da! Q-MAC Electronics Pty Ltd Q-MAC Electronics Pty Ltd Page 6 of 7

HEAD OFFICE 142 Hasler Road, Osborne Park WA 6017. Australia Tele!one" #61$ %242 2%00,&a'si(ile" #61$ %242 )%00 *(ail" info+(a'.'o( Web" ---.(a'.'o(



2 9 8 MHz during the night.

"he D-M@E M6-0 Magnetic 6oop @ntenna offers e/ceptional &'% performance.

1.( Su))ary

"he primar! factors that determine effective HF communications areB Fre#uenc!B "ime of da!B @ntenna !stemB &oise (&7. lectrical)B Eonductivit! of terrain (ground wave propagation)

Q-MAC Electronics Pty Ltd Q-MAC Electronics Pty Ltd Page 7 of 7 HEAD OFFICE 142 Hasler Road,

Osborne Park WA 6017. Australia Tele!one" #61$ %242 2%00, &a'si(ile" #61$ %242 )%00 *(ail"

info+(a'.'o( Web" ---.(a'.'o(



2 *t+er &nfor)ation

2.1 ,ut+or

Mr God Macduff 7c 7@ M% M% F%@ust

God Macduff is Managing irector of D-M@E lectronics which is a specialist supplier of HFEommunications to the Humanitarian @id Gelief and Militar! organisations. God Macduff wor*edwith Gacal 7EE for 0 !ears on the Iaguar ' tactical hopping radio and travelled e/tensivel!consulting with armies on their secure communication issues. "he D-M@E HF-0 hopping radio is inservice in J4 nations and has $een adopted $! Humanitarian @id Gelief @rm! >olice and%ntelligence organisations.

2.2 ,-out 0, lectronic!

D-M@E lectronics is specialist designer and manufacturer of HF "ransceivers. "he flagshipproduct the HF-0 is the worldKs smallest high performance HF 7 "ransceiver. "he HF-0 and D-M@E lectronics have $een awarded man! accolades and is currentl! used $! thousands of usersin over :0 countries worldwide. "he HF-0 is one of the most versatile HF transceivers availa$leand is suited to militar! paramilitar! and humanitarian aid and relief applications.

D-M@E offers the HF-0 in a variet! of configurations suited to manpac* vehicle and $ase stationapplications. @ full complement of accessories is also offered for use with the HF-0 includingantennas field $atter! charging accessories carr! pac*s,cases and more. @ll D-M@E products are$ac*ed $! the compan!Ks strong commitment to after sales service support and certified %C00#ualit! standards.

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