ab cd
Senior Member
EXAMPLES OF FAILURE OF SIMULATION SOFTWARE
Most of Collinears posted on internet are flawed design. These collinears are shown to be high gain by posting the supporting results of simulation. Almost no one posts results of actual measurements of Gain & SWR, or results of comparison with a standard benchmark antenna of known parameters.
It is my experience that these simulation software give results with errors which may be of the order of 5% to 10%, which is too high for accurate optimization of collinears. To highlight this, I optimized wire collinears by simulation, and calculated parameters of these collinears and a 1/4 wavelength (non-collinear) benchmark antenna. I then made prototypes and put on trial run with reference to benchmark antenna.
Results after optimization by simulation software were:
Benchmark antenna - Standard Cantenna: Gain = 1.48 dBi, SWR = 1.28
Antenna Under Test 1 - Coiled Cantenna: Gain = 2.99 dBi, SWR = 1.17
Antenna Under Test 2 - Franklin Cantenna: Gain = 3.13 dBi, SWR = 1.9
The simulation results show that both the Antennas Under Test should give better performance than Benchmark antenna. However when I made the prototypes using optimized dimensions given by simulation, and put on trial, results were opposite. This proved the unreliability of simulation results. I will now try to find the optimum dimension by trimming the prototypes.
I have actually made 2 whips under test only, and simply pulled out the 1/4 wavelength (69mm) whip of existing Standard Cantenna and inserted in its place the Whip under test. This made all other factors identical for the benchmark & under test antennas.
Prototypes (top to bottom):
Standard Cantenna, Coiled Cantenna, Franklin Cantenna
Simultion (top to bottom):
Standard Cantenna, Coiled Cantenna, Franklin Cantenna
Most of Collinears posted on internet are flawed design. These collinears are shown to be high gain by posting the supporting results of simulation. Almost no one posts results of actual measurements of Gain & SWR, or results of comparison with a standard benchmark antenna of known parameters.
It is my experience that these simulation software give results with errors which may be of the order of 5% to 10%, which is too high for accurate optimization of collinears. To highlight this, I optimized wire collinears by simulation, and calculated parameters of these collinears and a 1/4 wavelength (non-collinear) benchmark antenna. I then made prototypes and put on trial run with reference to benchmark antenna.
Results after optimization by simulation software were:
Benchmark antenna - Standard Cantenna: Gain = 1.48 dBi, SWR = 1.28
Antenna Under Test 1 - Coiled Cantenna: Gain = 2.99 dBi, SWR = 1.17
Antenna Under Test 2 - Franklin Cantenna: Gain = 3.13 dBi, SWR = 1.9
The simulation results show that both the Antennas Under Test should give better performance than Benchmark antenna. However when I made the prototypes using optimized dimensions given by simulation, and put on trial, results were opposite. This proved the unreliability of simulation results. I will now try to find the optimum dimension by trimming the prototypes.
I have actually made 2 whips under test only, and simply pulled out the 1/4 wavelength (69mm) whip of existing Standard Cantenna and inserted in its place the Whip under test. This made all other factors identical for the benchmark & under test antennas.
Prototypes (top to bottom):
Standard Cantenna, Coiled Cantenna, Franklin Cantenna
Simultion (top to bottom):
Standard Cantenna, Coiled Cantenna, Franklin Cantenna