In addition to providing a good match to the antenna, the Model 404-UL's Matching Unit has been optimized to match the antenna's specific common-mode-current characteristics, assuring problem-free installations, even in less than optimum locations.

HOW DID WE DO THIS ?

We began with extensive field measurements on several OCFD antennas, charting their common-mode-current problems, by band.

Using knowledge gleaned from K9YC's excellent paper on RF chokes, entitled "RFI-Ham", plus the charts on G3TXQ's web site, we optimized the Matching Unit's choking impedance to match the Model 404-UL's specific common-mode-current trouble area.