Sorry for not answering sooner... business is taking over ... as well as preparing flying since decent weather is on its way :-)
The idea of the above design is to use the work developed by the authors in the links below.
The simplest form of a collinear is to have stacked vertical half waves that radiates in phase, separated vertically by approx half wave.
The simplest solution to feed (connect) the radiating vertical half waves in phase is to use a very thin wire which is also a half wave. The radiating half waves are large diameter and the phase lines are small diameter.
If the large diameter elements are in phase and the small diameter elements are out of phase with the large diameter elements, radiation from the large diameter elements dominate.
Because the antenna is for receiving only, the phasing lines can use very small diameter without introducing any significant loss.
On the drawing, the lower half wave is center feed which makes matching to 50-75 Ohms more easy.
Using large diameter copper for the radiating elements helps reduce the antenna impedance at resonance and accentuate the ratio between radiating and phasing elements diameters to further minimize radiation from phasing lines.
You can see the lower half wave like the spider antenna which has been described before, at the end of which is connected a half wave phasing line which is connected to a half wave large diameter radiating line.
Adjusting the angle of the "spider legs" allows to adjust the impedance at resonance.
The below antenna should provide around 2-3 dB of gain compared to the spider antenna.
To improve radiation pattern, it might be a good idea to add a second ground plane, a quarter wave below the feed point of the lower half wave (65-70 mm below in our case).
coli jld2.png
Adding 3 radiating half waves above the spider should provide 5-6 dB of gain compared to the spider antenna.
In order to improve further the low angle radiation, it would be worth to try reducing progressively the diameter of the radiating elements (for example 10mm, 8mm, 6mm and 4mm for a 4 half wave vertical)
coli jld3.png
All this is theory and should be validated by experimentation.
The beauty compared to the coaxial version is that it does not depend from coaxial cable VF and it should be easy to construct with repeatable performance.
The idea of the above design is to use the work developed by the authors in the links below.
The simplest form of a collinear is to have stacked vertical half waves that radiates in phase, separated vertically by approx half wave.
The simplest solution to feed (connect) the radiating vertical half waves in phase is to use a very thin wire which is also a half wave. The radiating half waves are large diameter and the phase lines are small diameter.
If the large diameter elements are in phase and the small diameter elements are out of phase with the large diameter elements, radiation from the large diameter elements dominate.
Because the antenna is for receiving only, the phasing lines can use very small diameter without introducing any significant loss.
On the drawing, the lower half wave is center feed which makes matching to 50-75 Ohms more easy.
Using large diameter copper for the radiating elements helps reduce the antenna impedance at resonance and accentuate the ratio between radiating and phasing elements diameters to further minimize radiation from phasing lines.
You can see the lower half wave like the spider antenna which has been described before, at the end of which is connected a half wave phasing line which is connected to a half wave large diameter radiating line.
Adjusting the angle of the "spider legs" allows to adjust the impedance at resonance.
The below antenna should provide around 2-3 dB of gain compared to the spider antenna.
To improve radiation pattern, it might be a good idea to add a second ground plane, a quarter wave below the feed point of the lower half wave (65-70 mm below in our case).
coli jld2.png
Adding 3 radiating half waves above the spider should provide 5-6 dB of gain compared to the spider antenna.
In order to improve further the low angle radiation, it would be worth to try reducing progressively the diameter of the radiating elements (for example 10mm, 8mm, 6mm and 4mm for a 4 half wave vertical)
coli jld3.png
All this is theory and should be validated by experimentation.
The beauty compared to the coaxial version is that it does not depend from coaxial cable VF and it should be easy to construct with repeatable performance.
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