MMANA GAL Antenna Simulator: Modeling and Analysis Tutorial

4NEC2 simulation reveals collinear antenna two achieves maximum gain of 7.7 dBi at 85° elevation, dramatically outperforming antenna one's 2.33 dBi at 5°. Ground effects significantly impact radiation patterns—real ground modeling shows different characteristics than free space. Counterintuitively, some configurations show decreased gain at higher altitudes (50m vs lower positions). These findings demonstrate the complexity of real-world antenna deployment.

This section covers advanced radiation pattern analysis, power budgeting, loss density computation, and environmental effects on antenna performance. Engineers learn to compute radiation patterns in both free space and enclosed environments, analyze power distribution across incident, radiated, and dissipated components, and identify loss hotspots using loss density analysis. The segment emphasizes how surrounding structures dramatically alter antenna behavior, requiring systematic evaluation of multiple mounting positions and understanding of multipath propagation effects in real-world installations.

This segment explains how to analyze antenna radiation patterns using elevation and azimuth plots. The presenter demonstrates that real-world antenna performance differs from free-space theory due to ground reflections, which can actually improve gain compared to theoretical 2.15 dB isotropic reference. The analysis shows elevation angles, beamwidths, and the trade-offs between height and pattern symmetry.

Antenna patterns are polar plots showing field strength versus angle. Elevation patterns measure signal strength at different elevation angles at constant distance. A quarter-wavelength dipole produces maximum radiation at 90 degrees with a 130-degree 3dB beam width. Vertical antennas over perfect ground produce maximum radiation at approximately 26 degrees. Ground type dramatically affects patterns: perfect ground produces lowest angles, salt water similar to perfect, while average ground dramatically reduces low-angle radiation. Pattern shape is determined by interference between direct and ground-reflected radiation. Changing ground radial system size has minimal effect on pattern shape because reflection points are typically many wavelengths away.

NEC provides four ground environments affecting antenna performance: free space (no ground), perfect ground (ideal conductor), Sommerfeld ground (specify conductance and dielectric), and mini-NEC ground (NEC-2 compatible). Visualization tools display wire structures, current distributions, and radiation patterns with interactive features including zoom, rotation, and element reporting. Sommerfeld ground prevents direct wire connections due to numerical instability. Ground selection dramatically affects impedance characteristics, with perfect and mini-NEC grounds producing similar results while Sommerfeld enables realistic earth modeling.

This segment explains how wire insulation affects antenna performance. The instructor demonstrates adding a 'wire coat' with radius equal to wire radius plus insulation thickness. The segment explains that NEC2 models the surface of the wire, so insulation effectively shortens the antenna electrically. The instructor shows how to define velocity factor (0.98 for insulated wire) and how this affects wavelength calculations. The segment covers the relationship between speed of light, frequency, and wavelength, and how to incorporate velocity factor into the wavelength formula. The instructor demonstrates how to adjust antenna length based on velocity factor to achieve resonance.

The velocity factor corrects for the reduced speed of light in wires compared to free space. For copper wires, the velocity factor can be left at 0.95. When calculating antenna dimensions, this correction factor is essential because electromagnetic waves travel slower through conductive materials than through air.

Velocity factor accounts for the fact that radio waves travel slower through conductors than through free space. The normal velocity factor for antenna wire is approximately 0.93 to 0.95. To account for this, multiply the calculated quarter-wavelength length by the velocity factor. For example, multiplying 5.3 meters by 0.95 gives approximately 5.03 meters, which can be rounded to 5 meters as a practical starting point.

Velocity Factor refers to how different antenna materials and insulators affect the resonant length of an antenna by changing electron flow speed, with bare copper having a velocity factor of ~98-99% and insulated wire dropping to ~95%, meaning antennas with insulation or enclosures will be shorter than calculated using the standard 468/frequency formula; End Effect describes how high-voltage points at antenna ends create electromagnetic forces that make the antenna appear longer than its physical length, causing center-fed dipoles to resonate at lower frequencies than predicted and creating multi-band operation challenges for off-center fed antennas that require careful consideration of equipment selection (radios with tuners vs. fixed-length antennas).

Velocity factor is the difference between the actual length and electrical length of wire in antennas. For HF antennas using PVC-insulated wire, the velocity factor is approximately 96%, meaning the wire is 4% shorter than its actual physical length. To achieve proper resonance, builders must shorten the antenna by this percentage. The recommended approach is to cut wire to actual calculated size first, then use excess wire from velocity factor calculations for tie-offs or minor adjustments.

EZNEC software offers multiple versions (EasyNEC, EasyNEC Plus, EasyNEC Pro 2, and EasyNEC Pro 4) that utilize different NEC engines; while all versions use NEC2 code for basic straight-wire antennas, the Pro 4 version employs the more accurate NEC4 engine which is essential for modeling complex antenna structures with tapers, bends, and non-straight elements like rectangular loops with trombone ends, as NEC2 lacks sufficient accuracy for these geometries.

EZNEC software has evolved through multiple versions: EZNEC 7 (free, no support), EZNEC Pro 2 (paid, NEC-2 engine), and EZNEC Pro 4 (paid, NEC-4 engine). The original author Roy retired, but the software continues to receive updates. NEC-5 was developed by Jerry Burke for the Lawrence Livermore partnership, with Roy and Dan continuing development to fix bugs. NEC-5 version 13 is now available and is described as 'pretty damn Rock Solid.' NEC-5 fixes almost all bugs that existed in NEC-4, particularly when multiple inherent flaws are present. NEC-5 requires significantly higher segmentation density than NEC-4. NEC-4 could use approximately 7 segments per element, while NEC-5 needs much more segments. NEC-5 uses even segmentation (beginning of segment) while NEC-4 uses odd segmentation (center of segment). NEC-5 version 13 file size is approximately twice that of NEC-4.2, indicating more data and complexity. NEC-5 requires a minimum of approximately 60 segments per half-wave element. If segment size is shorter than element diameter, accuracy problems occur. NEC-5 positions the feed point at the beginning of the segment rather than the center like NEC-4, requiring even segment counts to center the feed point. End sections should have at least 2 segments. NEC-5 provides impedance analysis including real (R) and imaginary (J) components. The ideal is R=50 ohms and J=0.0. A negative J value indicates the driven element is too narrow or the loop is not wide enough. A positive J value indicates the element is too wide and needs reduction. NEC-5 tends to underpredict the size of reflector and first director when they are close-spaced with tapered elements and sharp corners. NEC-5 reveals compounded flaws in antenna models that NEC-4 missed. When multiple issues exist together (tapered elements, sharp corners, close-spaced elements), NEC-5 shows larger errors. NEC-5 SWR sweep analysis shows antenna performance across frequency. NEC-5 finalization involves iterative adjustments to achieve optimal performance. NEC-5 results are closer to real-world performance than NEC-4. NEC-5 can analyze wire loss effects on antenna performance. NEC-5 models built to these specifications will perform better in real-world conditions. NEC-5 accuracy depends on element size relative to wavelength. At 50 MHz, 16mm elements are relatively thin. At 2 meters, the same 16mm element is three times larger relative to wavelength, causing greater errors. NEC-4 uses a thin wire kernel that becomes less accurate at larger element sizes.

Antenna modeling programs like EZNEC use numerical electromagnetic code (NEC2) to simulate antenna performance by describing antennas as collections of straight wires, enabling analysis of patterns, gain, impedance, and interactions with other conductors; however, the accuracy of results depends entirely on how well the model represents the real antenna, as computers execute instructions literally without understanding intent.

Antenna modeling software like EZNEC uses the NEC (Numerical Electromagnetic Code) algorithm, originally developed at Lawrence Livermore Laboratories. NEC2 is free while newer versions require payment. The software breaks the antenna wire into segments (at least 10 per half-wavelength) and simulates electromagnetic behavior. Modeling requires specifying physical dimensions, wire type (copper/aluminum), height above ground, and ground conditions (free space, perfect ground, or typical earth). The software predicts radiation patterns, gain, front-to-back ratio, beam width, takeoff angle, feedpoint impedance, and SWR before physical construction.

SimNEC version 1.5 introduces automatic wire segmentation that places drive points and traps at exact specified locations by dividing wires into segments with a maximum length ratio of 2:1 between adjacent segments, eliminating the sawtooth impedance artifacts that occur when drive points are placed within existing segments in traditional NEC2 implementations.