Radio Wave Propagation #2. Maximize Space Wave Range! Direct & Ground Reflected Waves Explained. @technologiesdiscussion1676

Uploaded July 2025 | Updated September 2026, 1 week ago

Modes of Radio Propagation Playlist
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Radio Wave Propagation #2. Space Wave Propagation Formula Explained. Direct & Ground Reflected Waves

Space Wave Propagation is a mode of radio wave propagation where electromagnetic waves travel directly from the transmitting antenna to the receiving antenna, either along the line-of-sight (LOS) or after reflecting off the Earth's surface or troposphere.

A direct wave (or space wave) travels in a straight line from the transmitting antenna to the receiving antenna. This type of radio signaling is often called line-of-sight (LOS) communication.
Direct waves are neither refracted nor do they follow the Earth's curvature.
They can be blocked or reflected by obstacles and cannot travel beyond the horizon or behind obstructions.

Characteristics of Space Wave Propagation:
1. Frequency Range:
Typically used for VHF (30 MHz – 300 MHz) and UHF (300 MHz – 3 GHz) signals.
Commonly employed in TV broadcasting, FM radio, mobile communications, and radar systems.

2. Line-of-Sight (LOS) Dependency:
Since space waves travel in a straight line, the transmitting and receiving antennas must be within each other’s visible horizon.
Obstacles like buildings or mountains can block the signal.

3. Limited by Earth’s Curvature:
The maximum distance for LOS communication is determined by the height of the antennas.
Formula for LOS distance:

d = maximum distance (in meters)
hT = height of transmitting antenna (in meters)
hR = height of receiving antenna (in meters)

4. Tropospheric Effects:
Space waves can be slightly refracted due to changes in the troposphere's refractive index.
Sometimes, tropospheric ducting can extend the range beyond LOS under certain atmospheric conditions.

5. Multipath Propagation:
The signal may reach the receiver via multiple paths (direct + reflected waves), causing fading or interference.

Advantages of Space Wave Propagation:
Suitable for high-frequency communication (VHF/UHF).
Provides stable and high-quality signals within LOS range.
Less affected by atmospheric layers compared to sky wave propagation.
Disadvantages:
Limited range due to Earth’s curvature.
Requires tall antennas for long-distance communication.
Susceptible to obstacles and terrain blocking.

$Radio Wave Propagation #2. Maximize Space Wave Range! Direct & Ground Reflected Waves Explained. Modes of Radio Propagation Playlist https://www.youtube.com/watch?v=c3d_QpAxTd8&list=PLFxhgwM1F4yz5p8mJY5zyVLxMfs_avQEI For access to this presentation materials, membership is required: I need the Material PPT Sent me an email to Technologies.Discussion@gmail.com If you need the whole playlist material, send me email and we discuss. Give me some time to response. Thanks. Radio Wave Propagation #2. Space Wave Propagation Formula Explained. Direct & Ground Reflected Waves Space Wave Propagation is a mode of radio wave propagation where electromagnetic waves travel directly from the transmitting antenna to the receiving antenna, either along the line-of-sight (LOS) or after reflecting off the Earths surface or troposphere. A direct wave (or space wave) travels in a straight line from the transmitting antenna to the receiving antenna. This type of radio signaling is often called line-of-sight (LOS) communication. Direct waves are neither refracted nor do they follow the Earths curvature. They can be blocked or reflected by obstacles and cannot travel beyond the horizon or behind obstructions. Characteristics of Space Wave Propagation: 1. Frequency Range: Typically used for VHF (30 MHz – 300 MHz) and UHF (300 MHz – 3 GHz) signals. Commonly employed in TV broadcasting, FM radio, mobile communications, and radar systems. 2. Line-of-Sight (LOS) Dependency: Since space waves travel in a straight line, the transmitting and receiving antennas must be within each other’s visible horizon. Obstacles like buildings or mountains can block the signal. 3. Limited by Earth’s Curvature: The maximum distance for LOS communication is determined by the height of the antennas. Formula for LOS distance: d = maximum distance (in meters) hT = height of transmitting antenna (in meters) hR = height of receiving antenna (in meters) 4. Tropospheric Effects: Space waves can be slightly refracted due to changes in the tropospheres refractive index. Sometimes, tropospheric ducting can extend the range beyond LOS under certain atmospheric conditions. 5. Multipath Propagation: The signal may reach the receiver via multiple paths (direct + reflected waves), causing fading or interference. Advantages of Space Wave Propagation: Suitable for high-frequency communication (VHF/UHF). Provides stable and high-quality signals within LOS range. Less affected by atmospheric layers compared to sky wave propagation. Disadvantages: Limited range due to Earth’s curvature. Requires tall antennas for long-distance communication. Susceptible to obstacles and terrain blocking.$

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Why a Short Circuit (Circuit Theory) Isnt Always Short (The λ Mystery) The key difference between transmission line theory and circuit theory is electrical size. Transmission lines may be a considerable fraction of a wavelength or even many wavelengths in size. Circuit theory (DC / low freq) assumes that the physical dimensions of the network (or cable) are much smaller than the electrical wavelength. In transmission lines, the inductance (L) & capacitance (C) per unit length introduce a delay in the propagation of electrical signals. Heres why: 1. Basic Concept of Wave Propagation in Transmission Lines A transmission line can be modeled as a distributed network of series inductance (L) and shunt capacitance (C). When a voltage signal is applied, the inductance resists sudden changes in current, while the capacitance resists sudden changes in voltage. This interaction causes the signal to propagate as a wave rather than instantaneously. 2. Propagation Delay Due to L & C The speed of propagation (v) in a transmission line is determined by: Higher L (inductance) → Slows down signal propagation because it opposes rapid current changes. Higher C (capacitance) → Slows down signal propagation because it takes time to charge/discharge the line. Thus, the more L and C per unit length, the slower the signal travels. 3. Intuitive Explanation Inductance (L): Acts like inertia against current changes, causing a lag. Capacitance (C): Acts like a storage that needs time to fill up (charge) before voltage builds up. Together, they create a low-pass filter effect, delaying high freq components. Transmission line is a distributed parameter network, where voltage and current can vary in magnitude and phase over its length, while circuit analysis deals with lumped elements, where voltage and current do not vary appreciably over the physical dimension of the elements. 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Signal Behavior: Circuit Theory: Treats voltage and current as the same at all points in a node (no phase delay). Kirchhoff’s Voltage Law (KVL) and Kirchhoff’s Current Law (KCL) apply directly. Transmission Line Theory: Voltage and current vary along the length of the line due to wave propagation. Must account for time delay and phase shift due to finite propagation speed. Requires analysis using telegrapher’s equations, which describe wave behavior. 3. Key Parameters: Circuit Theory: Uses lumped elements: R, L, C. Impedance is simply the ratio of voltage to current (Ohm’s Law). Transmission Line Theory: Uses distributed parameters: Series resistance (R) and inductance (L) per unit length. Shunt conductance (G) and capacitance (C) per unit length. 4. Effects Considered: Circuit Theory: Neglects electromagnetic wave effects. No consideration for reflections or standing waves. Transmission Line Theory: Must account for: Reflections (due to impedance mismatches). Standing waves (when reflections interfere with incident waves). Signal integrity issues (Eg. ringing, crosstalk in high-speed circuits). 5. When to Use Which? Use Circuit Theory When: The circuit dimensions are ≪ λ (wavelength of the signal). Dealing with low freq power systems or analog circuits (Eg. audio frequencies). Use Transmission Line Theory When:$

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