Monday, September 8, 2014

A monoband 40M folded dipole

A monoband 40M folded dipole

 ( A single element "vari-loop" to you VHFers, HIHI)

 A borrowed MFJ 259B proved indispensible.


My roof is too small for a conventional 40 dipole or inverted V. Reading about double bazooka, I stumbled upon an article on folded dipole HF antennas (very rare). If I had money I would buy a high power 390 ohm non-inductive resistor and try to make it the more common TTFD dipole (Barker and williamson comes to mind) and make it broadband. But for now monoband fits the bill perfectly and possibly will not "affect" a proposed HF beam. This monoband design prevents half power loss in the resistor, to boot!


IN free space a dipole feedpoint would be about 75 ohms and a folded one about 200 to 300 ohms. My dipole is so heavily affected by its proximity to the roof so a "close to the roof" folded dipole presented about 50 ohms a stroke of luck.