【14MHzと18MHzの２バンド・ホイップ・アンテナ】 abstract I built a duo-band antenna for 14 MHz and 18 MHz. But the performance of that antenna was poor. The RF Power radiation efficiency was not good.　The reason was the stainless steel antenna element.　The antenna was a shortened version with a loading coil. The presence of stainless steel in the magnetic field of the coil caused a loss of RF power.　I was able to