7.7 GHz dual mode feed

thingiverse

Version 1.0 ! This is a low noise dual mode feed for X band weather satellite reception. It's a lower tuned version of the 8 GHz version published here with small edits: https://www.thingiverse.com/thing:4793665 Theoretically, best f/D is ~0.4 when lowest NF LNA are used, but max efficiency is at f/D~=0.6 so it might be suitable for offset dishes as well. The 3D print consists of the base, the waveguide and the dual mode section which are connected with screws. This work has been based on the W2IMU/N2UO 23cm design found here: http://ok1dfc.com/EME/technic/septum/N2UO%20opt.pdf. After printing, it has to be painted with a conductive paint and then electroplated in a bath. It is absolutely important the resulting surface to be as smooth as possible. Roughness will result in losses so patience when sanding/smoothing will pay off ! I used PLA and smoothed it with sandpaper starting from grit 500 up to 2000. Conductive paint and plating solution used were bought from https://www.tifoo.de/ Painting has to be carefully done paying attention not to leave any blank areas. If ABS/ASA are used I guess the smoothing process can be expedited in acetone vapors or the like. The final efficiency of the feed depends on surface roughness and the presence of any non-plated gaps. More info about weather/earth observation satellite reception can be found here: https://sv1cal.com/x-band-wx-satellite-reception/