Kenwood R-5000 Instruction Manual

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Contents

tic music from overseas broadcast stations or transmis-sions from Amateur radio stations and various industrial,marine, government, and military. It is also interesting tocollect reception or verification (QSL) cards. To ensuremaximum enjoyment of short-wave signals - how the sig-nals travel around the earth, the method of receiving sig-nals most effectively, the method of identifying thecountry broadcasting programs, etc.tion") over several hundered miles, usually between 15MHz and 30 MHz, and sometimes higher in frequency.Such a phenomenon also occurs with changes in seasonsor rotation cycle of the sun as well as unusual activities ofthe sun (change in the sunspot cycle every 11 years, unex-pected explosion on the sun, etc.). To cope with this, inter-national short-wave broadcast stations change their fre-quencies according to seasons or directions of radiowaves, or use different frequencies at the same time forbroadcasting the same program.7. REFERENCES7-1. ENJOYING SW RECEPTIONENJOYING SW RECEPTIONEvery country in the world has broadcast stations, andmost countries have Amateur radio stations. The earth isvirtually surrounded by innumerable radio waves, provid-ing us with information and news. Your receiver inter-cepts many of these transmissions.Radio waves cover a wide range of frequencies includinglong-wave (LF), medium-wave (MF), and short-wave (SW)or high frequency (HF). Since short-wave signals travelaround the earth, it is fun receiving exciting news and exo-Propagation of Radio Waves By the IonosphereThe earth is surrounded by the atmosphere. The atmos-pheric molecules existing between 50 km and 500 kmabove the earth collide with ultraviolet rays and electronsemitted from the sun, and a layer of electrons and ions isformed. This layer is called the ionosphere and it has acharacteristic of refracting radio waves. Radio wavesemitted from the antenna of a transmitter can be classifiedas surface waves and ionospheric waves. Surface wavestravel along the earth directly, and are used mainly for me-dium frequency AM broadcast and TV and FM broadcast.Ionospheric (sky) waves travel a long distance becausethey are refracted repeatedly between the ionized layerand the earth. As short-wave broadcasts propagate byionospheric waves, their signals often reach around theearth. The surface wave tends to weaken at HF and short-wave frequencies and therefore travel only a short dis-tance, while ionopheric waves persist as the frequency in-creases (up to a certain point, determined by ionization in-tensity) and travel long distance with little path loss. Ultrahigh frequencies pass through the ionized layer, and thusthe service area is limited to a short distance from the an-tenna. The ionosphere is divided into three layers, D, E andF.The electron density in the layer is increased in steps ac-cording to the distance from the sun. High frequencywaves are refracted by the F layer and travel a long dis-tance.The state of the ionized layer is closely associated with therelative positions of the sun and the earth and also withthe activity of the sun. The D and E layers almost disap-pear at night, while the F layer changes in height and den-sity depending on daytime or night time, and changes theupper frequency limit to be reflected. Occasionally,"clouds" of ions will drift through the E layer, causingstrong signal propagation (called "sporadic E propaga-30