- G4CQM Homebrew/DIY Antenna Specialist -
VHF/UHF/SHF HAM (AMATEUR) RADIO YAGI AERIAL DESIGNS

4X1UN - SIMPLE 3 ELEMENT 144MHz (2M) YAGI

Breaking News...

Today June 6th 2007 at 16:24 UTC Shalom Cohen 4X1UN (KM72JB) with his 3 Element Yagi had a record breaking contact working CT1HZE (IM57NH). A staggering distance (QRB) of 4008.06KM! To date Shalom has had QSO's with 30 countries: Israel, Egypt, Jordan, Syria, Turkey, Russia, Ukraine, T9, Z3, LZ, HA, I, YO, SP, OK, YU, HV, OE, DL, EA6, CT, SV, SV5, SV9, 5B4, ZC4, 9A, 9H, ER and S5, all worked with this Yagi. Well done to Shalom!

If you're just starting out on 144MHz take note, Shalom's results are testimony to what can be achieved with a simple setup.

73's from Derek G4CQM

Construction

Shalom Cohen 4X1UN asked me to design for him a simple Yagi that could be constructed from materials in his junk box. It is based on 'Direct Feed' also known as 'Direct Connect', the element lengths and spacing delivering a natural 50 ohms feed impedance. It will produce a forward gain of 7.2dBi and better than 20dB F/B.

Use 1/2 inch (13mm) pipe/tubing for the elements. They need to be located above a metal boom and insulated from it. Alternatively, use a non-metallic boom and attach the elements directly or pass them through the boom, drilling large holes to do so.

08/09/2009 - Please note that I have updated the build of this yagi after checking with YO7 PRO, the NEW DIMENSIONS shown below;

Element Position          Element Length

0                                 Reflector = 1040.6mm
417.2mm                    Driven Element = 960.6mm
737mm                       D1 = 842.8mm

The Driven Element dimension is end to end, so cut two pieces 475.3mm long and provide a 10mm gap. Although many text books say you need to include a 1:1 Balun, in reality this Yagi works without. However, if you can find any suitable Ferrite slugs slip one over the feeder at the feedpoint.

The Yagi is what I call a 'Flat Liner', having a broad frequency response, gain and impedance characteristic. Finally, remember that this design is based on FREE-SPACE dimensions, so make sure the elements are either mounted on insulators above the boom or use a non-metallic boom!

Julian Hardstone G3TFR contacted me on the 12th of March 2009, he has constructed the 4X1UN yagi by modifying a commercial Band 2 antenna, the result is stunning! See new section below...

73's from Derek G4CQM

Shalom Cohen 4X1UN and his three element Yagi

Components used by Shalom

Seen here are the components used by Shalom and what he had to say!

"Well, thanks to your kindness I have built the 3 element yagi for 2m. It is wonderful! It is even better than I expected. I get almost always a few S Points more than before and now I can talk to my father 4X6UN clearly."