This is a new antenna I invented. At the lower frequencies it acts like a fat monopole, and at higher frequencies it’s a tapered slot antenna. it shows a very nice SWR below 2:1 from 150MHz to 10GHz. Of course I didn’t invent either type, but I’m positive I’m the first to combine them into one antenna.
Below are pics of a 12DBi helical. I made the helix support from laser cut lexan. The first 1/4 turn feed transition was the critical part in tuning.
Below are more variations of the tapered slot / fat mono. The one in large blue foam is an extended low frequency model. With the larger ground plane and copper tape “top-hat” it’s now usable to 70MHz.
For my Ham Radio HF station I made my 4:1 balun for my Off-Center-Fed antenna. The core is a 140-77 ferrite, wound with teflon wire. Plots shown with 200 Ohms on output. So far good for a couple hundred watts.