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In order to build the antenna I bought copper pipes with an outer diameter of 12 mm, 4 copper T-pieces, RG58 cable, SMA connectors as well as some 3D-printed parts and a plastic rod but you can also use a self build wooden fixture.
Therefore, the optimized crossed dipole antenna with crossed dipole reflector is going to be build in the following: Prototyping However, the copper pipes used for the crossed dipole reflector are much cheaper, more handy and easier to mount outside (little contact surface for wind). The antennas gain characteristic for RHCP is seen below:īy comparing the two antennas with their different reflectors (conductive plane, crossed dipole) it is seen, that the crossed dipole reflector has nearly the same 3dB onpening angle and a maximum gain difference of 1.7 dB. The antennas maximum gain is 5.6 dBi with an 3dB opening angle of 94 degrees. An optimized Sonnet Model employing a crossed dipole with crossed dipole reflector is downloadable here.
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The signal that is reflected by the passive reflector, has a phase difference of a full wavelength resulting in constructive interference towards space. An image of a RHCP antenna is seen below: Again it is placed a quarter wavelength below the crossed dipole.
The simulation model is configured for the use of 1cm thick copper tubes used for water installation.Īnother and cheaper way of enhancing the antennas gain towars space is using a passive crossed dipole as a reflector. The antennas gain characteristic for RHCP is depicted below: The maximum simulated RHCP gain is 7.3 dBi and it’s opening angle is about 100 degree. An image within Sonnet of this Right Hand Circular Polarized (RHCP) setup is depected below:Ī 137 MHz optimized crossed dipole Sonnet model with reflector is downloadable here. In order to increase the antennas directive gain, there are several techniques that are usable.įirst, a conducting reflector placed a quarter wavelength beneath the cross dipole enhances the antennas gain directed to space. It depends on the signal transmission lines length attached to the antenna.
By using a second dipole perpendicular to the first one and connecting two arms respectively, it is possible to make a righthand or lefthand circular- polarized antenna. By shortening the dipole by about 3% a cancellation of the imaginary impedance is possible.
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It is a standing wave antenna which has in free space an input impedance of 73+j43 Ohm. We start with a simple one-half wavelongth dipole antenna. If you are like me and want to design and build the antenna yourself continue reading. In principle for my setup i am using a parallel fed turnstile antenna. Introduction to Antenna Analysis Using EM Simulators If you also want to start building your antennas using Sonnet, the following book is a very good start: (fully operational only NOAA18 and 19) Simulation and Designįor the simulation of the Antenna i am using the IE-MOM electromagnetic simulation Tool Sonnet Software. Antenna Simulation, Design and Prototyping Operating Frequencyįollowing operating frequencies and bandwidth are needed for the three NOAA satellites: NOAA #
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Further i am going to introduce you to the needed Software SDR sharp, Orbitron as well as WX2IMG and provide download links. We are starting with the design of the antenna including simulations, some theory and a build prototype.
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If you also want to receive such images, i am going to show you how to do it. Typical images from my setup are seen below:
With a quite easy and low-cost setup, it is possible to receive and decode signals from the NOAA satellites. The cool thing about this satellites is, that they use an analog image transmission system called Automatic Picture Transfer (APT). Since then several launches occured and nowadays () only NOAA18 and 19 are fully operational. The National Oceanic and Atmospheric Administration (NOAA) did launch its first satellite Trios 1 in 1960.