2:1 (100:50) Baluns are useful between 50 ohm coax and 100 ohm balanced lines for loops, cubical quads, log periodics and other antennas where the impedance at the end of the feedline is 100 ohms (1/2 wavelength feedline).
Model CU-2.25:1-4-9-1200 is a 2.25:1, 4:1 and a 9:1 voltage unun housed in a NEMA enclosure box (4" x 4" x 2") with one stud for 2.25:1 (112.5 ohms), one stud for 4:1 (200 ohm load) and another stud for 9:1 (450 ohm load) outputs, each capable of input power levels up to 1200 watts PEP when used with a matched load. (You can only have 1 load connected).
The 2.25:1 ratio takes 50 ohm input and matches it to a 112.5 ohm load (useful for 100-150 ohm antenna load). The 4:1 ratio takes 50 ohms input and matches to 200 ohms output and the 9:1 ratio takes 50 ohm input and matches to 450 ohms output between 1-31 MHz under 1.5 SWR under matched load conditions.
A great multi-purpose unun for 31 or 43 foot fiberglass verticals, end fed non-resonant antennas, traveling wave verticals, etc. Quad core, Ruthroff style unun with side ground terminal for adding a counterpoise or radials as an option. Now you don’t need to buy three separate ununs – just buy the CU-2.25:1-4-9-1200 and pick the output ratio that provides the best match for your antenna tuner!
Impedance transformations from 3-30 MHz are shown below:
The Unun provides multiple taps for impedance conversions of: