What are the reasoms to prefer a half wave dipole antenna over one wavelength antenna?
Hi,
Most important thing about half dipole antenna is radiation analysis. It gives more directive pattern as compared to one dipole antenna.
GAIN is high.
Thanks,
It's length (half of the wavelength) gives you the better performance than other lengths..... It may be gain, efficiency, directivity, return loss, etc.....
I got the following picture from a book.
I think the gain of the half wave dipole is higher than the full wave length antenna.
I also see that the input impedance of the full wave dipole is infinity.
Then for which reasons specifically the half-wave dipole is still preferred over the full wave dipole?
I would say it is due to more practical considerations such as physical size. A quarter wave on CB and VHF is ~102", but full wave would be 34', which is not a very practical whip antenna on vehicle. On spacecraft, a double dipole or quad monopole configuration is often considered due to directivity and polarization loss. Circular polarization is generally used to mitigate this, but sometimes a satellite is launched to receive a signal that has already been implemented for ground-based applications only (e.g. Automatic Dependent Surveillance Broadcast signals from aircraft are vertically plane polarized). A satellite, depending if it is tumbling, only two-axis stable or lagging in terms of its attitude determination (or large errors in pointing accuracy) may be completely mismatched if using only one dipole and will use something like perpendicular double dipole antennas or a quad monopole. The Radio Receiver Instrument (RRI) as part of the Enhanced Polar Outflow Probe (ePOP) payload on the Canadian CASSIOPE small satellite is a digital receiver that operates from 10-18 MHz and connects to 4 tubular monopoles usually configured as two orthogonal 6-m dipoles. I find the best texts for practical considerations are HAM radio related and taking the course to complete my license has been invaluable to my research.
Vikesh, choosing one antenna over requires more than A or B.
What is the problem you are trying to solve?
What is the coverage pattern you need to provide?
What is the required range?
What is the like RF power you intend to use?
Are the radios mobile?
Do you have a ground plane under the antenna?
For many mobile installations you would like to have a ground independent antenna, which is a good reason to chose a half wave dipole, that is end fed. The feed point has a high but not infinite, impedance. You may need a small counterpoise(about 5% lambda) to balance the antenna against, depending on how you feed your antenna and do the impedance transformation between the transmission line and feed point. This can provide a lower take off angle of radio than a quarter wave mono-pole over a ground plane. Again, does depend on your use case.
Thanks for the remarks, it was just a question to gain more knowledge why a half wave anetnna is preferred over a one wvavelenth antenna
Antenna choice is a practical balance between radiation pattern and efficiency. Then there is always the material/cost and mounting/location factors...
The primary lobes in the radiation pattern are orthogonal to the half wave dipole. Where as there are more lobes in less useful directions on a full wave dipole and your feed point impedance is not conveniently close to the impedance of you transmission line. You will have to make a choice between current fed or voltage fed impedance transformers at your antenna feed point, this will affect your efficiency.
Nafati, Its from famous book * Antenna Theory: Analysis and Design 4th Edition * . In chapter 4 , page #180. In this book Prof. Balanis also mentioned your name to the *preface *.
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