Re: Mesh size for 10GHz
Neil Smith G4DBN
There is a loss calculator for mesh reflectors on the W1GHZ site at http://www.w1ghz.org/antbook/conf/Mesh_Reflector_Loss_Calculator.xlsxtoggle quoted messageShow quoted text
There is a lot of useful stuff elsewhere in http://www.w1ghz.org/antbook/preface.htm
There is also a mesh loss calculator on the VK3UM (SK) EMECalc program. I see that the VK3UM site is currently suspended by the ISP, I thought it had been adopted by WIA to preserve it for posterity? Still available in Google cache and on the web archive, but link rot is starting to set in. There is a copy at https://www.vk5dj.com/doug.html
If the mesh is not welded, there are additional losses, but the mathematical treatment of those is very tough indeed.
Bigger issue is if the surface is not an accurate parabola, with flats and creases. Again, the maths are horrible on the research papers I found.
The mesh loss is bidirectional, so you start to see leakage from behind the dish as the reflectivity drops. Probably not important if the dish is up on a pole pointing at the horizon, but not good for EME, as the ground is rather hot compared with cold sky.
Main point is that a mesh dish up in the air works 100% better than a solid one in a crumpled heap on the ground, although above 40mph or so, a mesh dish has almost the same wind load as a solid one the same size.