AN-SOF is a simulation software for antenna modeling, analysis, and design.
AN-SOF is a simulation software for antenna modeling, analysis, and design.
At Golden Engineering we are passionate about antenna simulation. On this last day of the year we want to give you our Log-Periodic Christmas Tree made with AN-SOF:
We thank all our clients, users and people who collaborate so that the AN-SOF Antenna Simulator project continues to grow day by day.
Happy New Year!
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This version of AN-SOF has new functions and options:
Tip: double click on table items to instantly display plots.
REQUEST AN-SOF 7.90 TRIAL VERSION >
Enjoy AN-SOF!
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Magnetic loop antennas find extensive application within the realm of amateur radio pursuits. One prevalent design employs a dual loop configuration, wherein a larger loop, equipped with a tuning capacitor at one end, is magnetically linked to a smaller loop positioned inside it. The smaller loop serves as the connection point for the coaxial cable, which feeds the antenna. This antenna’s construction is remarkably straightforward, as it capitalizes on the adaptability of coaxial cable wires for assembly. It is important to emphasize that the interplay between the two loops is rooted in induction rather than physical linkage.
Illustrated in the accompanying image, the simulation delves into an instance where the larger loop, fashioned from RG-8 cable, spans a diameter of 70 cm, while the smaller loop, crafted from RG-6 cable, boasts a 15 cm diameter. Maintaining a separation of 2 cm between the loops at the antenna’s base, the provided diagram outlines the requisite tuning capacitor settings for achieving resonance across five distinct frequencies: 3.5, 7, 14, 21, and 29 MHz.
Sited a meter above a typical ground plane, the antenna showcases a radiation pattern that diverges from the conventional toroidal shape anticipated for a small loop positioned in free space. The color scale displayed on the loops indicates the current intensity corresponding to each resonant frequency.
Facilitating precise simulations of this antenna design, the AN-SOF Antenna Simulator leverages the Conformal Method of Moments featuring curved segments. This enables the meticulous replication of loop contours. A noteworthy attribute of AN-SOF lies in its use of an exact Kernel, which accommodates close proximity of both loops at the antenna’s base.
The simulator further streamlines the calculation process by permitting sequential and automated execution of the antenna’s resonance calculations across the five specified frequencies. This eliminates the need for manual execution of each calculation. To access this feature, navigate to the AN-SOF main menu and select Run Bulk Simulation under the “Run” category. This function allows you to effortlessly run calculations on the five “.nec” files, available for download via the provided button. Importantly, this functionality is available even with the trial version of AN-SOF.
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The Quadrifilar Helix (QFH) antenna, also referred to as the QHA, stands as an excellent choice for signal reception from the satellites of the National Oceanic and Atmospheric Administration (NOAA). This antenna configuration boasts omnidirectional capabilities and is composed of four helically wound wires, intertwining to create a helix—an intricate geometric arrangement that imparts distinctive properties to this antenna.
The design depicted in the image below showcases a configuration with a diameter of approximately 0.14 times the wavelength (λ) and helix lengths of 0.4λ. A resonant frequency of 137.5 MHz ensures its optimal functionality, accompanied by a bandwidth spanning 6%, defined by a standing wave ratio (SWR) below 2. This composition serves a dual purpose: enabling efficient signal reception from NOAA satellites while effectively mitigating external interference.
A noteworthy observation emerges when evaluating the antenna’s radiation pattern under varying conditions. In a vacuum environment, the radiation pattern orients downward when the coaxial cable, simulated as a voltage source in simulations, connects to the antenna’s apex. This phenomenon is depicted in the leftward radiation pattern. However, when the QFH antenna is positioned in real-world scenarios, a substantial transformation occurs. Placing the antenna at an elevation of 5 meters and introducing a real ground plane yields an entirely distinct radiation pattern.
The resultant pattern in this real-world configuration displays omnidirectional properties within the azimuth plane. Notably, this pattern showcases multiple lobes concerning elevation angles. The practical application of this radiation pattern is invaluable for effectively capturing signals from a variety of satellite orientations. AN-SOF allows us to accurately model the behavior of these intricate helices, courtesy of the implementation of the Conformal Method of Moments, which utilizes curved segments to faithfully represent the contour of the helices.
In summary, the Quadrifilar Helix (QFH) antenna stands as an ingeniously designed configuration, adeptly capturing signals from NOAA satellites. The configuration of four helically wound wires offers omnidirectional capabilities and robust interference suppression.
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This Moxon antenna variant resonates at 145 MHz.
Input Impedance: 47 Ohm
Bandwidth: 7% (VSWR < 2)
Gain: 6.3 dBi
F/B: 19 dB
Beamwidth: 130°H / 80°V
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This 4-element biquad array resonates at 434 MHz. The wires that connect the driven element to the reflector work as a two-wire transmission line that allows us to obtain an input impedance of 50 + j0 Ohm.
It may be noticed that the polar plots are on a log scale. ARRL-style log scaling is coming in the December release of AN-SOF!
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This is a 4 element broadband directional antenna. More than 50 MHz of bandwidth (SWR < 1.5) around 285 MHz. Gain 7 to 8 dBi. Length 0.52 m and maximum width 0.6 m.
The driven element is shaped like a double arrow and has a folded parasitic element right in front of it.
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Explore the new AN-SOF User Guide >, where you will find detailed information about its many features, as well as step-by-step examples and tips to help you quickly move forward with your antenna modeling projects.
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From this link > you can download 5 examples of antenna models that have less than 50 segments, so the calculations can be run with the trial version of AN-SOF:
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It is an array of two tightly coupled loops with a bi-directional pattern. Both loops are linked to share a single feed point. This antenna can operate in the 14 to 28 MHz bands with the appropriate impedance matching. It is self-resonant when the perimeter of each loop is around one wavelength. In this example, each loop is 3 x 4.5 m and the resonant frequency is 19.8 MHz.
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A balun can be modeled in AN-SOF using an equivalent generator, as the figure below shows. Since voltage sources admit an internal impedance, we can adjust its resistive part to match the antenna input resistance.
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This design is for 5 bands on a single pole. Each “J” corresponds to a band and therefore the feed point changes depending on the frequency. The resonance frequency is indicated in each case, which can be changed by moving the feed point. The height is about 5 m.
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Enjoy!
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Here is a relatively compact array of 5 square loops for 145 MHz. It does not need a matching network since the input impedance is practically 50 Ohm. Gain 12 dBi. Beamwidth 50 deg. F/B 20 dB.
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These are compact, lightweight antennas that can be used for DX applications. This 2-element array is the simplest we can build to get a directional antenna using delta loops. It is practically resonant with 50 Ohm of input impedance near the band center. This is an example where we need to enable the Exact Kernel option in AN-SOF since we have sharp angles between wires.
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Enjoy this new version!
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In amateur radio satellite communication, the use of directional antennas is a fundamental necessity. Operating on both the VHF and UHF bands with a single antenna can present a considerable challenge. In this article, we introduce a dual-band antenna design that covers both VHF and UHF bands, accomplished by combining two distinct antenna types: the Moxon antenna for VHF frequencies and the Yagi antenna for UHF frequencies. One of the notable advantages of this design is that it utilizes a single feeding point.
The Moxon antenna, also known as the Moxon rectangle, stands as a simple yet mechanically robust antenna configuration composed of two elements: a driven element and a parasitic element. It derives its name from the renowned radio amateur, Les Moxon, with the call sign G6XN. In essence, the Moxon antenna resembles a Yagi-Uda antenna with two folded dipole elements, one serving as the driven element and the other as the reflector element. A tunable gap exists between these two folded dipoles, allowing for adjustments to minimize the VSWR (Voltage Standing Wave Ratio) at VHF frequencies. Consequently, it is a mechanically tunable antenna that eliminates the need for an impedance matching network. In our dual-band design, as illustrated below, the Moxon segment of the antenna serves as the excitation point.
The accompanying figure also depicts the Yagi-Uda portion of the dual antenna. This section adheres to the conventional Yagi array configuration, comprising a reflector element, a driven element, and three directors. However, the driven element in this context does not receive direct excitation; instead, it is powered indirectly through electromagnetic induction from the driven element of the Moxon array. The gap separating the Moxon and Yagi sections of the combined antenna can be mechanically adjusted to minimize the VSWR at UHF frequencies.
In the analyzed frequency ranges, this VHF/UHF dual-band antenna exhibits self-resonance with an input impedance close to 50 Ohms, obviating the requirement for a matching network. To optimize performance in each band, fine-tune the gaps as indicated in the figure below.
Additionally, the figure provides VSWR curves as a function of frequency. In the upper section, it is evident that the antenna resonates at 147 MHz, while in the lower section, it resonates at 442 MHz. The figure also presents radiation patterns for both frequency bands, with gains of 6.3 dBi at VHF and 12 dBi at UHF.
Detailed AN-SOF models, along with antenna dimensions and calculations, are available for download through the buttons located below the figure.
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AN-SOF 7.10 is now available for download!
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2-element quad antennas are very popular due to their compact size and gain similar to a more element Yagi. In addition, they can be designed to obtain an input impedance of 50 Ohm.
This design can operate at 27.5 MHz. We have added a script that allows us to plot the gain and front-to-back ratio as a function of element spacing. See this video >.
We can see that both cannot be maximized at the same time, but it is preferable to choose the maximum F/B since the gain changes relatively little.
To create the Scilab script, we started from a basic design in AN-SOF and then exported it as a *.sce file.
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A half-wave dipole would have a length of 40 meters in this band (3.75 MHz), difficult to install at home due to lack of space. Not to mention the complaints from our neighbors.
A spiral loop is attractive for its small size and relative ease of tuning because it is basically an inductor to which a variable capacitor is connected at the feed point to achieve resonance. However, the radiation resistance is extremely small, on the order of milliohms and therefore the efficiency is very low.
Unfortunately any small loss severely affects the antenna efficiency, such as losses in the capacitor, wires, interconnections, solder joints, surrounding objects, ground plane, to name just a few. In fact, this antenna can be tuned and get a wide bandwidth thanks to all the losses. The maximum radiation occurs upwards when the antenna is installed vertical to the ground plane, so some have suggested installing it horizontally. We should emphasize, however, that it is a popular design due to its ease of installation and small size, but we must be careful because high voltages can be expected, especially in the tuning capacitor.
This AN-SOF model consists of a frame of 50 cm on each side (0.00625 of the wavelength) with 7 turns of wire. This is another example where we need to simulate with very short wire segments, very close to each other and bent at right angles.
In these results we can see the effect on the input resistance of adding losses in the ground plane and surrounding objects, such as a wall,
Perfect ground: 4 milliohm
“Cities industrial poor” ground: 1.3 Ohm
“Cities industrial poor” ground + wall: 49 Ohm
This design can be easily transformed into a multi-band antenna by shorting turns of wire, much like a variable inductor, to make it operate on the 40, 30 and 20 meter bands.
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Small helical antennas for the 433 MHz ISM band are a good example where we need advanced software that has the ability to model:
AN-SOF includes all these features.
In this example, a perfect ground plane is used to get the input impedance: 48 Ohm, very close to the 50 Ohm of the antenna datasheet. We must subtract 3 dBi from the gain to obtain the gain in free space. It is a simple model, but it coincides very well with reality.
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Nathan Cohen in the US fractalized the quad loop based on the Minkowski square and invented an array of two elements. The biggest advantage of fractal antennas is that we get a wide bandwidth with a small size.
This simulation shows that we can almost double the bandwidth with a 3-element array. It has a reflector, a driven element, and a director. These are the results for the 20 m band (~ 14 MHz),
Quad size ~ 290 x 290 cm (0.14 x 0.14 of a wavelength)
Element spacing ~ 280 cm
450 KHz bandwidth (VSWR < 2) around 14.5 MHz
6 dBi gain
10 dB F/B
80° beamwidth
Vertical polarization
It has less gain than could be achieved with a 3-element Yagi, but it has a relatively large bandwidth and is a very compact antenna. It does not need a matching circuit and its impedance is 50 Ohm at resonance, so it could be fed directly through a 50 Ohm coax.
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And last but not least, in this link > you will find the model of a Yagi-Uda antenna with variable element spacing. Follow the instructions therein and run the scripts to get the gain of a 3-element Yagi antenna as a function of the element spacing.
Enjoy!
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