I've been thinking of using a 1 foot diameter prime focus dish with the transverter. The Chaparral-type feed has two parts - the one that attaches to the board and the Chaparral feed itself. I was thinking that it might be possible to use a piece of brass tubing with an outside diameter of 5/32 inches (0.156 inches, ~ 4 mm) with an inside diameter of 5/64 inches (0.078 inches - ~2 mm). Brian WA1ZMS told me that the SHF Micro 1 foot diameter dish performs acceptably at 122 GHz. He has even used one at higher frequencies. I am currently using this dish with a piece of brass tubing (circular waveguide) and a reflecting plate on 76 GHz.
The f/D ratio for this dish is 0.6. That gives a focal length of 7.2 inches. I can machine a short section of 5/32 inch diameter brass rod with a center hole 5/64 inches in diameter, but I can only machine a couple inches. I could possibly use another piece of brass tubing with an ID of 5/32 inches to connect to this that would be long enough to use as the feed. I inquired of K & S Metals about the cost of a brass tubing that has an OD of 5/32 inch and 0.04 inch thick walls. This would give an ID of 0.076 inches, which would be acceptable. They told me there is a minimum order for 12-inch sections of this tubing of 24 at $4.17 each. I neither need nor want to purchase 24 of them unless someone wants a group order.
Any discussions or suggestions on this?
73, Zack W9SZ