Polar Circle Amateur Radio Adventure

Propagation Overview

It has never been a secret that long-range communication in the amateur bands is primarily dependant  upon the ionosphere, however it is essential to visualize the structure of the ionosphere  and to understand more thoroughly the basic theory behind the usage of sky-wave methods of transmission if effective use the ionosphere is to be made.

The Ionosphere's Structure

The ionosphere's overall structure consists primarily of three ionized layers ranging from 35 to 215 miles or so above the earth. The region lowest in height found at about 35 miles extending to 70 miles is called "D" layer and for all practical purposes, is useless to the amateur. Instead of reflecting radio waves, the "D" layer acts as an impediment and attenuates the signals strength to sometimes completely absorting 80 and 160 meter signals .

Sunspot Cycles and Ionospheric Variations

Ultraviolet  radiation from the sun is believed to be the source of energy which ionizes the ionospheres numerous layers. This belief is constituted  on the basis of what is known as the 11-year sunspot-cycle.  Over a period of a few years, the number of sunspots  increases to a peak and then gradually declines, like this moment. The duration from  one sunspot peak to another usually covers about 11 years. During its peak , communicating conditions are excellent especially for 20, 17, 15, 12 meters bands and are even better on 10 meters.  We are approaching to the sunspot down and for worst conditions, contacts should be not so good. at a sunspot minimum or "sunspot dip" communicating ranges e poor with very few band openings. There  also exist what is known  as  ionospheric storms and when they occur, the critical frequencies drop considerably and absorption of radio signals in the ionosphere is substantially increased.  These ionospheric storms are resultant of certain sunspot activity. They usually last from few hours to several days.

Propagation Data

If the amateur has in his shack a wealth of propagation charts or just on or two of them, he will be much better off than the other amateur  who doesn't have any.  By a simple connection through internet to the Institute for Telecommunication Sciences and Astronomy, you can receive regularly prediction muf's for the upcoming days and other information.

We use this discussion to record suggestions about the features that should or shouldn't be included in our software, and to engage in a public dialog regarding the merits of various requests for enhancements. Anyone is welcome to submit suggestions.

This page contains links to all of the public discussions for this project. We maintain a separate protected web for internal project discussions and notes.

Here is a good place to describe a list of your hobbies, projects or interests.

This page contains links to other Very Interesting places for this project. We maintain a separate protected web for internal project discussions and notes. Look at predictions for June.

W6EL Prop^TM

W6EL Prop predicts ionospheric (sky-wave) propagation between any two locations on the earth on frequencies between 3 and 30 MHz. There is no charge for W6ELProp when used for non-commercial purposes.Download W6ELProp v2.70 (479,795 Bytes)

Requirements Discussion

Unfortunately, for most of us, the ionosphere was not in usual  well behaved self this year, but, although we reached the poorest conditions possible for the higher frequency bands. 

A smoothed  sunspot  number of 105 is forecast for May and June. A seasonal decrease is forecast for DX conditions. While fewer openings are expected during both months.

DX propagation should be possible to one area of the world to another practically around-the clock on 20 meters. This should be the best band for DX propagation during the hours of darkness and through the sunrise period. 

Propagação

A noção de propagação das ondas cobre a presença ou ausência de factores favoráveis à circulação das ondas electromagnéticas, no espaço, de um emissor para um receptor.

Todos sabemos que estes factores são influenciados pelo comprimento de onda utilizado e e pelas condições criadas nas camadas ionosféricas.importância perponderante nas comunicações.

Com o ciclo solar em "queda" algumas das bandas que proporcionam contactos fáceis em DX passam estar mais tempo cerradas e sem condições. Se as condições de propagação são favoráveis, esses contactos DX serão possiveis mesmo quanso se dispõe  de uma potência bastante reduzida, e correlativamente, nenhuma condição será possível se estas condições  são desfavorávei8s, qualquer que seja a potência usada.  Devido a todas estas razões que acabamos de citar é necessário utilizar todos os instrumentos que nos possam ajudar a obter as informações necessárias a calcular ou a sugerir previsões que nos indiquem as datas, horas e frequências mais propícias para a comunicação rádio.

 

A estrutura da  Ionosfera

A propagação indirecta ou reflectida permite às ondas electromagnéticas terem um alcance bastante maior do que o horizonte visual. A energia HF pode assim efectuar diversos percursos de ida e volta antes de ser captad por uma antena situadas a dezenas milhares de quilómetros , estes contactos a que chamamos "DX". O sinal recolhido por uma estação longínqua será mais ou menos atenuado pela absorção pelo solo e pela perda consecutivca de potência.

As camadas ionosféricas que são assim capazes de reflectirem as ondas compôem-se de ar ionizado devido à acção dos raios ultravioletas do sol, sendo portanto condutoras de electricidade. No caso das comunicações rádio, interessam-nos sobretudo as três cdamadas inosféricas D, E e F.

D-Situada a cerca de 70 a 80 Kms

E-Situada a entre 100 e 130 Kms

F-Situada a 1500 a 4000 Kms

A presença da actividade solar é determinante nas condições de propagação. 

 

Cálculo de Previsões de Propagação 

W6EL Prop^TM

W6EL Prop é um programa que permite calcular as condições de propagação entre dois locais na terra nas frequências entre os 3 e os 30 MHZ. Este programa é gratuito quando usado sem fins comerciais.Download W6ELProp v2.70 (479,795 Bytes)

 

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Last updated: Maio 27, 2004.