Building A Giant $200 3D Corner Reflector Antenna for GOES, Moon Bounce and Pulsar Detection
A corner reflector antenna is basically a monopole antenna with a metallic 'corner' reflector placed behind it. The reflector helps the monopole collect signals over a wider aperture resulting in signals coming in stronger from the direction that the corner is pointing at. In past posts we've seen a homemade tinfoil corner reflector used to improve reception of the generic stock RTL-SDR monopole antenna, and a larger one was used in a radio astronomy experiment to detect a pulsar with an RTL-SDR.
Recently The Thought Emporium YouTube channel has uploaded a video showing how to build a large 2 meter 3D corner reflector out of readily available metal conduit pipes and chicken wire. While the antenna has not been tested yet, they hope to be able to use it to receive weather satellite images from GOES-16, to receive moon bounce signals, to map the Hydrogen line and to detect pulsars.
I had tried a couple of months ago building a “2D” corner reflector for UHF out of some metal cloth and PVC (as a reflector for an LPDA); I found keeping it stable was a big challenge and that it was really heavy.
Chicken wire might be lighter-weight; although I think to reduce weight further I might try aluminum window screen fabric.
You tried the copper weave cloth? They type that is marketed to block signals?
a great pdf about 3d corner reflector antennas
It’s not just size that brings antenna gain. The max. useable frequency of this design should be just a few 100 MHz, limited by the size of the holes in the mesh, which have to be small in relation to the wavelength to provide any acceptable reflection. Also the surface looks to uneven/rough to achieve much gain.
To get an idea look at 2d Corner reflector antenna designs to give you an idea of reflector requirements. They consists of a dipole driven element mounted in front of two flat rectangular reflecting screens joined at an angle, usually 90°. Here normal tubing with sufficient min. spacing can be used to provide more stable designs see https://en.wikipedia.org/wiki/Corner_reflector_antenna .Therefore I wonder if the real gain is anywhere near the theoretical gain they hope to achieve.
Even with the theoretical gain a corner reflector antenna, they will unlikely be able to receive any reflections from the, at least not with the transmitt power and antenna gains available to HAM operators doing moon bouncing.
The surface roughness is proportional to the desired wavelength of operation. So a surface that is “a bit rough” at 2GHz may be entirely acceptable at 300MHz.
For *3D* corner reflectors, the optimal feed appears to be a 3/4-lambda monopole, spaced about 0.6lambda from the vertex.
These things *do* work, it’s just that their gain reaches a limit somewhere around 2.5 to 2.8lambda for the side dimensions. Above that, and you aren’t adding any more gain, just structural mass. The gain on these doesn’t scale the way it does with parabolic dishes. But they are very easy to make, certainly easier than a dish.
Due to the size twisting or warping (hope that are the correct words) will further reduce the theoretically achieveable antenna gain. Looking at the design I wonder if they have thought of using an elevation/azimuth rotor at all, to focus on the signal source.