A major advantage of antennas with direct feeding is simple construction and insensitivity to the surrounding environment. The path to increasing gain is in reducing the antenna impedance. However, the matching circuit introduces losses back into the system. In optimal design, the advantages of OWA yagi outweigh other types of antennas. Among OWA yagis are also antennas calculated using Antenna Model and EZNEC 5+. G0KSC.
For vacation use, a light 4 element yagi is excellent. Calculated gain is 8.63dBi in free space and F/B ratio 19.22dB.. The design is very tolerant of manufacturing accuracy. I collected the remains of material from old antennas and waste from the manufacture of others and created a compact, light antenna for 50 MHz.
Compared to the G0KSC design, I used plastic element holders that you can purchase, for example, from Jirka OK5IM.. Since they are for elements with a diameter of 10 mm, I calculated the antenna in MMANA once again. The results and measurements confirmed the good design of G0KSC.
Dimensions of G0KSC yagi
R: 3000mm, diameter 10mm
Z: 2940mm, diameter 14mm, telescopic end 12mm
D1: 2770mm, diameter 10mm
D2: 2614mm, diameter 10mm
Boom: 25 x 25mm, length 2460mm
Placement of elements on the boom
R: 0mm
Z: 967mm
D1: 1270mm
D2: 2402mm
Draft of G0KSC yagi using MMANA
The most effort in manufacturing is taken by the radiator. It is divided into two halves, which is mounted insulated above the boom. I used insulators from an old antenna. It is a nylon cylinder with a drilled hole of 14mm in diameter. A tube is passed through it so that a feeder can be connected to the soldering eyes at the end. Using U-clips, it is attached to an aluminum plate. By tightening the U-clips, a firm attachment of the radiator is achieved. The feeder is connected through balun made of five turns of coaxial cable placed close to the radiator. The balun is fixed with plastic zip ties. The installation of the other components is very simple thanks to the plastic mounts.
Finished G0KSC yagi
Measurement VSWR The meter confirmed the expected flat VSWR curve. According to the measuring instrument, it is even 1:1 in the most commonly used segment of the 50 MHz band. The antenna is quite sharp despite the short boom and needs to be aimed precisely. This indicates that the suppression of signals (and interference) from other directions is excellent.
The net time to build the antenna is about 4 hours. Due to its simplicity and good characteristics, it is an excellent antenna to get acquainted with the 50 MHz band.