Yesterday I have just built this EFHW antenna for my QDX and in a few weeks my QCX+ 20M band to be built in May: using a HB9ZHK kit and 10 meters of wire (precisely cut for 14.060MHz with a SWR of 1.13:1). I will add a very tiny 150pF SMD C1 capacitor in parallel of the primary to improve ?its efficiency in higher frequencies. This antenna is just spread out of my 4th floor balcony using a 5 meter long telescopic fishing pole.?
Today the 150pF SMD capacitor was soldered (second photo). It was not an easy task for a 80 years old OM with eyesight his age and shaky hands! You can compare the size of C1 with the size of the BNC plug. I had then to cut 10cm of wire then 10cm again and finally 6cm more because the addition of C1 modified the antenna but it works well now giving a SWR of 1.3:1 at 14.066MHz then 1.1:1 at 19.733MHz and 1.9:1 at 27.066MHz. If I want to use it on other bands I will have to add several lengths of wire connected by gold plated banana plugs.
Pierre - FK8IH