A Cardioid Small Loop
The so-called Loop on Ground (LoG) is a small loop antenna with a cardioid-shaped radiation pattern in the horizontal plane, used for reception.
The loop has a 110 Ohm resistor connected to its top, while the antenna terminals are located at the bottom. One of the terminals is connected to ground by a vertical wire, forming a monopole. This is the secret to getting this antenna, despite being small, to be directional.
The image below shows the radiation patterns obtained with and without grounding.
Frequency: 4.5 MHz
Loop diameter: 1 m
Height above ground: 2 m (average real ground)
The segmentation used in the Conformal Method of Moments is observed over the antenna. Very few segments are needed because it is a small antenna in terms of the wavelength.
Log-Periodic Christmas Tree
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!
145 MHz Moxon Antenna
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
Biquad UHF Antenna Array
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!
Broadband Directional Antenna
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.
An HF Skeleton Slot Antenna
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.
145 MHz 5-Element Array of Square Loops
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.
17 m Band Spider Delta Loop
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.
Moxon-Yagi Dual Band VHF/UHF Satellite Antenna
This model is self-resonant (50 Ohm) in the analyzed frequency range, so it does not need a matching network. Adjust the indicated gaps to minimize the VSWR.
Script for Modeling 2-Element Quad Array
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.
Array of Snowflake Quads
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
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.