Search results
An 80-10 end-fed half-wave antenna can be a very good performing part of an HF station. But its performance depends heavily on a well-designed and carefully constructed 49:1 unun, which matches the long wire impedance to within tuning range of operation. But the perfor-mance of an end-fed antenna is also very dependent on height above ground.
This project assembles a 49:1 ferrite-core (“FT”) type #43 transformer that matches 50 ohm input to 2500 ohm end fed antenna. It is optimized for 3.5/7/10/14 MHz but will work reasonably well on all amateur bands from 80 meters thru 10 meters with a 135 foot length of wire and a short connection to ground.
Detailed Build Instructions for the 80-10 end-fed half-wave antenna with 49:1 unun: Noji-Article-80-10-EF-HW.pdf Source: https://noji.com/hamradio/pdf-ppt/noji/Noji-Article-80-10-EF-HW.pdf
Figure 2 shows the complete schematic view of a typical EFHW antenna system. Briefly, the 100pf/2kv cap across the primary of the impedance matching transformer is there to allow better tuning in the 10 meter band. The transformer is a step-up with an impedance ratio of 49:1, and wound on a type 43 toroid core.
The design used here is taken from Tom Rauch W8JI, a very respected authority on amateur antennas. This G5RV design is intended to support the 80-, 40-, 20-, and 15-meter bands, but requires a tuner, due to excessively low DC resistances at resonance.
Download The Mini 49:1 UNUN Instruction manual here. Antenna wire lenghts. The End Fed Half Wave antenna requires to cut one of halfwave lenghts.
This antenna, which works on 10, 15, 20, and 40 meters, has a very high impedance of around 2,500 Ohms. The kit includes the parts needed to construct a 49:1 impedance matching network, which will transform the impedance to 50 Ohms, which will suit most transceivers.
