Left Border Content - RF Cafe
Windfreak Technologies
LadyBug Technologies LB5944A RF Power Sensor - RF Cafe

About RF Cafe

Kirt Blattenberger - RF Cafe Webmaster

Copyright: 1996 - 2024
    Kirt Blattenberger,


RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling 2 MB. Its primary purpose was to provide me with ready access to commonly needed formulas and reference material while performing my work as an RF system and circuit design engineer. The World Wide Web (Internet) was largely an unknown entity at the time and bandwidth was a scarce commodity. Dial-up modems blazed along at 14.4 kbps while typing up your telephone line, and a nice lady's voice announced "You've Got Mail" when a new message arrived...

All trademarks, copyrights, patents, and other rights of ownership to images and text used on the RF Cafe website are hereby acknowledged.

My Hobby Website:


Header Region - RF Cafe
Electronics World articles Popular Electronics articles QST articles Radio & TV News articles Radio-Craft articles Radio-Electronics articles Short Wave Craft articles Wireless World articles Google Search of RF Cafe website Sitemap Electronics Equations Mathematics Equations Equations physics Manufacturers & distributors Engineer Jobs LinkedIn Crosswords Engineering Humor Kirt's Cogitations RF Engineering Quizzes Notable Quotes App Notes Calculators Education Engineering magazine articles Engineering software Engineering smorgasbord RF Cafe Archives RF Cascade Workbook 2018 RF Symbols for Visio - Word Advertising RF Cafe Homepage Thank you for visiting RF Cafe!
Sub-Header - RF Cafe Exodus Advanced Communications Best in Class RF Amplifier SSPAs

Navy Electricity and Electronics Training Series (NEETS)
Module 10 - Introduction to Wave Propagation, Transmission Lines,
and Antennas
Chapter 2:  Pages 2-41 through 2-47

SURFACE WAVES travel along the contour of the Earth by diffraction.

Surface Waves - RF Cafe

SPACE WAVES can travel through the air directly to the receiving antenna or can be reflected from the surface of the Earth.

Space Waves - RF Cafe

SKY WAVES, often called ionospheric waves, are radiated in an upward direction and returned to Earth at some distant location because of refraction.
NATURAL HORIZON is the line-of-sight horizon.
RADIO HORIZON is one-third farther than the natural horizon.
The IONOSPHERE consists of several layers of ions, formed by the process called ionization.
IONIZATION is the process of knocking electrons free from their parent atom, thus upsetting electrical neutrality.
RECOMBINATION is the opposite of ionization; that is, the free ions combine with positive ions, causing the positive ions to return to their original neutral atom state.


The D LAYER is the lowest region of the ionosphere and refracts signals of low frequencies back to Earth.
The E LAYER is present during the daylight hours; refracts signals as high as 20 megahertz back to Earth; and is used for communications up to 1500 miles.

Layers of the ionosphere - RF Cafe

The F LAYER is divided into the F1 and F2 layers during the day but combine at night to form one layer. This layer is responsible for high-frequency, long-range transmission.
The CRITICAL FREQUENCY is the maximum frequency that a radio wave can be transmitted vertically and still be refracted back to Earth.

 - RF Cafe

The CRITICAL ANGLE is the maximum and/or minimum angle that a radio wave can be transmitted and still be refracted back to Earth.



Critical Angle - RF Cafe

SKIP DISTANCE is the distance between the transmitter and the point where the sky wave first returns to Earth.
SKIP ZONE is the zone of silence between the point where the ground wave becomes too weak for reception and the point where the sky wave is first returned to Earth.

Skip Zone - RF Cafe

FADING is caused by variations in signal strength, such as absorption of the rf energy by the ionosphere.


MULTIPATH FADING occurs when a transmitted signal divides and takes more than one path to a receiver and some of the signals arrive out of phase, resulting in a weak or fading signal.

Multipath Fading

Some TRANSMISSION LOSSES that affect radio-wave propagation are ionospheric absorption, ground reflection, and free-space losses.
ELECTROMAGNETIC INTERFERENCE (EMI), both natural and man-made, interfere with radio communications.
The MAXIMUM USABLE FREQUENCY (MUF) is the highest frequency that can be used for communications between two locations at a given angle of incidence and time of day.
The LOWEST USABLE FREQUENCY (LUF) is the lowest frequency that can be used for communications between two locations.

Lowest Usable Frequency - RF Cafe



OPTIMUM WORKING FREQUENCY (FOT) is the most practical operating frequency and the one that can be relied on to have the fewest problems.
PRECIPITATION ATTENUATION can be caused by rain, fog, snow, and hail; and can affect overall communications considerably.
TEMPERATURE INVERSION causes channels, or ducts, of cool air to form between layers of warm air, which can cause radio waves to travel far beyond the normal line-of-sight distances.

Temperature Inversion - RF Cafe

TROPOSPHERIC PROPAGATION uses the scattering principle to achieve beyond the line-of-sight radio communications within the troposphere.

Tropospheric Propagation - RF Cafe




A1.   Induction field and radiation field.
A2.   Induction field.
A3.   Radiation field.
A4.   Fundamental frequency.
A5.   Harmonic frequency or harmonics.
A6.   30 meters.

A7.   5 megahertz.
A8.   Vertically polarized.
A9.   Direction of wave propagation.
A10.   Shifting in the phase relationships of the wave.
A11.   Troposphere, stratosphere, and ionosphere.
A12.   Stratosphere.
A13.   Whether the component of the wave is travelling along the surface or over the surface of the earth.
A14.   Radio horizon is about 1/3 farther.
A15.   Sea water.
A16.   (a) electrical properties of the terrain (b) frequency (c) polarization of the antenna
A17.   High energy ultraviolet light waves from the sun.
A18.   D, E, F1, and F2  layers.
A19.   D layer is 30-55 miles, E layer 55-90 miles, and F layers are 90-240 miles.
A20.   Thickness of ionized layer.
A21.   Critical frequency.
A22.   (a) density of ionization of the layer (b) frequency (c) angle at which it enters the layer
A23.   A zone of silence between the ground wave and sky wave where there is no reception.
A24.   Where ionization density is greatest.
A25.   A term used to describe the multiple pattern a radio wave may follow.
A26.   Selective fading.
A27.   Natural and man-made interference.


A28.   Natural.
A29.   Man-made.

A30.   (a) filtering and shielding of the transmitter (b) limiting bandwidth (c) cutting the antenna to the correct frequency
A31.   (a) physical separation of the antenna (b) limiting bandwidth of the antenna (c) use of directional antennas
A32.   Regular and irregular variations.
A33.   Regular variations can be predicted but irregular variations are unpredictable.
A34.   Daily, seasonal, 11-year, and 27-days variation.
A35.   Sporadic E, sudden disturbances, and ionospheric storms.
A36.   MUF is maximum usable frequency.  LUF is lowest usable frequency.  FOT is commonly known as optimum working frequency.
A37.   MUF is highest around noon. Ultraviolet light waves from the sun are most intense.
A38.   When LUF is too low it is absorbed and is too weak for reception.
A39.   Signal-to-noise ratio is low and the probability of multipath propagation is greater.
A40.   Frequent signal fading and dropouts.
A41.   FOT is the most practical operating frequency that can be relied on to avoid problems of multipath, absorbtion, and noise.
A42.   They can cause attenuation by scattering.
A43.   It can cause attenuation by absorbtion.
A44.   It is a condition where layers of warm air are formed above layers of cool air.
A45.   It can cause VHF and UHF transmission to be propagated far beyond normal line-of-sight distances.
A46.   Troposphere.
A47.   VHF and above.
A48.   Near the mid-point between the transmitting and receiving antennas, just above the radio horizon.


NEETS Table of Contents

Footer - RF Cafe high frequency PCB of PCBONLINE
Right Border Content - RF Cafe
Werbel Microwave - RF Cafe
Berkeley Nucleonics Model 855B Signal Generator - RF Cafe

Please Support RF Cafe by purchasing my  ridiculously low−priced products, all of which I created.

These Are Available for Free