Antenna Design
Good antennas tend to be worth what they cost.
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Antenna Design Information & Software

Good antennas rank very high in importance. Find a station with a consistently-strong signal and you probably have found a station with a good antenna.

Good antennas contribute greatly to the communication abilities of both transmitting and receiving stations. A length of wire long enough to load a transmitter against a poor ground easily can require several times as much transmitter power as a simple dipole installed at ideal height. A directional antenna that concentrates radiated power at an optimum vertical angle of radiation in a desired direction can provide many decibels of additional improvement, allowing use of less transmitter power or providing stronger received signals.

You will find a wealth of free antenna design information and software below.

  • Photos Antenna Photo Gallery Photos of antennas, supporting structures, and antenna-related components ...
  • 6-Meter / 17-Meter Multiband K7EFX Multiband "3-Half-Wave 6-Meter," "Half-Wave 17-Meter" Rotatable Antenna The purpose of this build was to replace my 12/6-Meter inverted-vee with a rotatable antenna ...
  • Bifilar-Wound Bifilar-Wound Antenna Traps Two identical plastic-insulated wires are wound together on a former (as with a bifilar RF choke). The two wires are then connected series-aiding. Inductance resonates with distributed turn-to-turn capacitance at the trap frequency which is set to the exact value by adjusting fractional coil turns. A high-voltage, high current, tuning capacitor is not needed. An overall length/diameter ratio of 1.5 to 2.5 is recommended ...
  • Bottom Load Bottom-Loaded Vertical Antennas & Coil Design For given vertical antenna height, diameter and operating frequency, this program calculates base feedpoint impedance, loading inductance or capacitance. For given coil length and diameter the number of coil turns and wire gauge are also calculated ...
  • Cage Dipole Resonant Frequency, Bandwidth and End-Effect of a Wire-Cage Dipole Antenna Each half of the dipole consists of a cylindrical cage of parallel wires, the wires being connected together at their ends. The purpose of the cage is to increase the effective diameter of the antenna. This causes an increase in capacitance and a decrease in inductance per metre of length. The characteristic impedance Zo = Sqrt(L/C) of the antenna and the equivalent L & C series tuned circuit therefore decreases. Inductive reactance is reduced and so is Q ...
  • Cage Inverted-L Antenna for 160-Meters Ron, K4SX, describes results obtained from a Cage Inverted-L antenna that can be installed in much less space than is required for installation of most transmitting antennas that perform well in that part of the spectrum.
  • Coax Trap Design of Antenna Traps Using a Solenoidal Coil of Coaxial Line This program allows a practical designer to do what he normally does - wind some turns on a coil former and then vary number of turns until the resonant frequency with internal self-capacitance is the value required. Predicting accuracy is as good as the accuracy of measuring coil dimensions: 1 or 2 percent ...
  • Coil-Loaded Short, Coil-Loaded, Ground-Mounted, Vertical or Slanting Antennas The feedpoint impedance of a short vertical antenna has a high capacitive reactance. To present a purely resistive load to the transmitter somewhere in the system there must be an inductive reactance to cancel it. All coils have a loss resistance and the question arises - where in the system can a large coil be conveniently located such that power-radiating efficiency is maximised ...
  • Dipole Tuner + Coax Line + Balun + Balanced Line + Dipole A high dipole, centre-fed via a balanced-pair transmission line, is an efficient multi-band radiating system at all frequencies above that at which the end-to-end dipole length is about 0.35 wavelengths. But site topography and accommodation often require a coaxial cable between the balanced line and the transmitter ... (see updated verison below)
  • Dipole (updated) Performance of a Dipole, Feedline and Balun followed by a Tuner A high dipole, centre-fed via a balanced-pair transmission line, is an efficient multi-band radiating system at all frequencies above that at which the end-to-end dipole length is about 0.35 wavelengths. But site topography and accommodation often require a coaxial cable between the balanced line and the transmitter ...
  • Dipole SWR vs. Freq Half-Wave Dipoles - Input Impedance & Feedline VSWR vs. Frequency This program analyses both simple and folded dipoles. Folded dipoles allow a higher impedance and hence lower loss feed line to be used. The operating bandwidth is also marginally higher for a given acceptable feedline VSWR. It is assumed antennas are remote from the ground - heights greater than 0.75 lambda ...
  • End-Fed End-Fed Antennas, Ground Systems, Tuning & Matching This program models a wide range of end-fed antennas used with a ground system of radial wires. For each model the inductance and capacitance values of three alternative impedance matching networks are computed to match to a 50-ohm line. Results include RF power losses in the principal parts of the radiating system and overall radiating efficiency. Input Z of the ground electrode is estimated ...
  • Halfwave Vertical Half-Wavelength Vertical Antenna and Tuner This program analyses the performance of resonant 1/2-wavelength antennas. The antenna may be vertical or sloping. It is matched to a 50-ohm feedline by an L and C parallel tuned circuit which is connected between the base of the antenna and ground. The coax feedline is tapped down the tuning coil. The ground connection can be via plates, rods or buried radial wires which need not be extensive ...
  • Helical Model and Predict Helically Wound Vertical Antennas This program models and predicts the performance of a helically wound vertical antenna, mounted immediately above a ground plane, top-capacitance-loaded with a vertical rod or whip. The antenna is designed to be fed between its base and the ground plane operating at its 1/4-wavelength resonant frequency ...
  • Inverted-L, Vertical & Dipole Input Impedance of Inverted-L, Vertical & Dipole Antennas Amateurs begin and very often remain with simple wire antennas. The most important characteristic of a simple antenna is its input or feedpoint impedance, Zin. Zin may need to be transformed in some way to be connected to the transmitter and/or receiver ...
  • Inverted-V Performance of an Inverted-V 1/2-Wave-Resonant Dipole + Any Feedline Inverted-V antennas are popular because, relative to horizontal dipoles, erection costs are lower, and/or because the size of the site is smaller than the overall length of the full size horizontal dipoles they substitute. Efficiency is less than a horizontal dipole of similar height, but the radiation pattern is more omni-directional which may be considered to be an advantage ...
  • Load Component Location, Type & Value of a Loading Component to Resonate an Antenna Wire It is often required for the input impedance of an antenna wire, open circuit at its other end, to be purely resistive. In general, Zin has a large reactive component but this can always be 'tuned-out' by inserting a loading coil or loading capacitor at some position along the wire from the feedpoint. The type of loading component needed depends on the overall wire length and operating frequency. For lengths shorter than 1/4-wave a coil is necessary. The type of component and value for longer lengths depends on its location along the wire ...
  • Loop 1 Single-Turn, Transmitting Loop Antennas of Various Regular Shapes over a Range of Operating Frequencies For given perimeter, conductor diameter and height above ground this program computes the radiating efficiency and other characteristics of single-turn, transmitting loop antennas of various regular shapes over a range of operating frequencies. The program applies to perimeters of half-wavelength or smaller ...
  • Loop 2 Transmitting Loop Antennas when the Perimeter is Less than 0.75 Wavelengths Long This program assists with the design and estimates the performance of single turn, rectangular, transmitting loop antennas when the perimeter is less than 0.75 wavelengths long at the operating frequency. A 50-ohm feeder is assumed. Any item of input data may be changed on a "What-if" basis ...
  • Loop 3 Multi-Turn, Square, Frame (or Loop) Receiving Aerials Given the length of one side of the frame, number of turns of wire, the wire diameter and ratio of winding pitch to wire diameter, this program computes inductance, wire HF loss resistance, quality-factor Q, and other results of interest. Stray shunt capacitance is computed and for a given resonant frequency, the setting of the variable tuning capacitor is shown ...
  • Loop 4 Large, Horizontal, Loop antennas Fed via Balanced or Coaxial Lines Large loops are multiband and are most useful when the loop perimeter is more than half-wavelength at the lowest frequency of interest. The lowest self-resonant frequency is when the perimeter is 1/2-wavelength. SWR on the feedline is very high when the perimeter is near to an odd-number of 1/2-wavelengths ...
  • Magnetic Loop Single-Turn Transmitting Loop Antennas of Various Regular Shapes Magnetic loop antennas are so named because most of the energy in the near field is contained in the magnetic component and very little in the electric component. This applies to all loops with perimeters less than 1/2-wavelength, i.e., those with a tuning capacitor connected between nearly-touching ends ...
  • MMANA ModelingMMANA Antenna Modeling Program MMANA is an antenna analyzing tool based on the moment method introduced in MININEC (Mini Numerical Electromagnetics Code) Version 3. MININEC should not be confused with NEC, which is a large antenna analysis program written in FORTRAN and designed to run on main-frame computers. Early versions of MININEC were written entirely in BASIC and the computation engine source code was published as a PDS in MININEC Version 3. That BASIC source code was ported to C++ and compiled to provide faster and more memory-efficient computer execution. A graphical user interface also was added that makes MMANA much easier to use than MININEC version it was ported from ...

    • MMANA Images Images of the four most important MMANA screens

  • MMANA Modeling Program Tutorial A step-by-step inverted-coat-hanger antenna MMANA modeling program design example MMANA is a powerful antenna modeling program that is fascinating to experiment with. It can model a wide range of antenna types, calculate radiation patterns, power gains, front-to-back ratios, feed impedances, bandwidths, the effects of loading inductors, capacitors and resistors, the effects of resonant traps, the effects of some types of transmission lines, and other things of interest to anyone interested in antennas. However, there are important issues that can totally invalidate results, there are some annoying software bugs to avoid, many program capabilities are not immediately obvious, and the documentation is limited ...

  • Mid-Load Design & Performance of Compact, Centre-Loaded Dipole Antennas When the overall length of an HF dipole is less than about 1/3rd wavelength radiating efficiency decreases rapidly. Additional loss occurs not in the antenna itself but in the feedline due to high SWR, and also in the tuner ...
  • Mobile Loop Mobile HF Loop Antennas Radio Amateurs most often use inductively-loaded vertical whip antennas in HF mobile applications, but is there a better alternative despite the long popularity of vertical whips? ...

  • Not a Trap A Two-Band Antenna Wire Loaded with an L and C Parallel-Tuned Circuit The LC parallel-tuned circuit is constructed exactly like an antenna trap. It is located in the antenna wire and used as L or C loading at two other resonant frequencies. Parallel-tuned circuits have a reactive impedance on either side of resonance. On the low frequency side there is a +ve inductive reactance. On the high frequency side there is a -ve capacitive reactance ...
  • R, X & SWR Input Impedance and SWR of an Antenna in the Vicinity of Resonance This program models an 80m band vertical and a 1/2-wave dipole. It demonstrates the effects on SWR of changing frequency in the vicinity of antenna resonance. Antenna lengths are approximately 20 and 40 metres respectively ...
  • T-Antenna Performance of a T-Antenna Tuned Against a System of Buried Radial Wires A dipole, centre-fed via a twin feeder, can be used as a "T" antenna at LF and VLF, but a good ground system and a physically large tuning coil are necessary to obtain a useful radiating efficiency. This program assists with design by predicting the power lost in the various parts for a given power input ...
  • T-Antenna 2 The Simple Tee Antenna A vertical or sloping wire is connected to the approximate centre of a straight horizontal top wire. The vertical wire may be curved inwards towards the shack and is fed at its bottom end via a series L or C. The top wire provides a capacitance load on the vertical and increases the vertical's radiation resistance but does not itself contribute much to the radiation ...
  • Top Hat Performance of Short, Vertical, Top-Capacitance-Loaded Antennas Capacitance loading of a short vertical antenna can improve radiating efficiency better than inductance loading. Best possible improvement for a 2/3-height loading coil relative to base loading is typically 3 dB. But a large top hat can improve performance by more than 6 dB. In this program the hat is a number of horizontal radial wires or rods optionally surrounded by a wire circle ...
  • Trapped Dipole Trapped Dipole Radio Antennas A 'trap' is a coil and capacitor in parallel having a very high impedance at its resonant frequency. If a trap is inserted at some point along an antenna conductor, that part of the antenna beyond the trap is isolated from the active part and the feedpoint. When a pair of traps are inserted in a dipole, equidistant from the feedpoint, that part of the antenna between the traps when of correct length becomes a halfwave dipole at F2, the trap resonant frequency ...
  • Tuned Trap Behaviour of a Tuned Trap Inserted in an Antenna Wire A trap is a parallel L and C tuned circuit operating at or near to its resonant frequency. Its function is to isolate the wire beyond the trap from the wire which precedes it. It cannot do this perfectly even at the trap's exact resonant frequency but there is a band of frequencies over which performance can be considered to be satisfactory ...
  • Vertical Loaded Coil-Loaded Vertical Antennas Operating in Quarter-Wave Resonance Antennas are constructed from three contiguous cylindrical sections: mast, coil and rod, the length and diameter of each part being set by the experimenter. For a given resonant frequency the program computes the number of coil turns ...
  • Very Short Very Short, Helically Wound, Monopole Antennas The main reason for using a helically wound antenna is to obtain a low height at a given frequency. Ideally, it should be self-supporting - not too slender ...
  • Whip Received Signal Strength Expectations using a Whip Antenna with an Un-Un An un-un is an unbalanced-to-unbalanced transformer. In this program it is assumed to be 100% efficient. The un-un impedance ratio is selectable, either 1:1 or 9:1 with impedance step-down from antenna to coax line. No other means of matching the antenna to the coax line impedance is used ...
  • Windom The Windom Antenna The Windom is a 1/2-wave horizontal dipole fed off-centre by a single-wire non-resonant transmission line. It is named after L.G.Windom, W8GZ who described it in September 1929 QST ...
  • Wire Selection Antenna Wire Considerations Many types of wire can be used to construct wire antennas. Some of the choices include copper, copper-clad steel, copper-plated steel, aluminum, aluminum-clad steel, aluminum-plated steel, steel, hard-drawn, soft drawn, solid, stranded, bare, and insulated. None of those options ...

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