A four element antenna for the 50 MHz Amateur Radio Band
The 4 over 4 Yagi for use on 50 MHz:
A detailed written article on this antenna in a stacked version appeared in the German FUNKAMATEUR magazine from April 1997 page 448+.
After working three years with a homemade DL6WU type 6-element-antenna, I was intended to build something new as the old antenna decided to fall apart. So I came to this one. After some calculations I came to a 4 element yagi. I found an antenna of similar size which is made by 'KONNI-Antennen, Esselbach, Germany' and is prized around DM 120.- or US $ 80.-. The antenna has a balun of RG58 cable and a N-socket fixed already. This antenna already met the calculations almost with the element distances, but the elements had to be modified, which increased gain from 7.6 dBi to 9.2 dBi and gave a F/B-ratio of ca. 15 dB.
A view of the four element against a fantastic aurora on 27 August 1997.
So here is the table of the new element dimensions. The reflector needs to be cut and the 2nd director has to be prolonged. The elements are mounted insulated above the boom
|Element #||Position||center-to-end element length||Diameter|
|1 st Director||1.605||1.33||12|
|2 nd Director||2.682||1.32||12|
I use a folded dipole with coaxial balun on this antenna.
Stacking the antenna
I use two lengths of 75 Ohm coaxial cable of 3/4 wavelength (i.e. around 3.1 meters per length) for stacking. ELNEC® gives a value of 11.9 dBi for the antenna system. The stacking distance is 4.1 meters.
I made a 4 over 4 element antenna system. It outperforms my old homemade 6 element antenna. The narrower beamwidth eliminated some TVI problems I had, because of the smaller vertical beamwidth. This system did a very good job in the last summer of 1996.
Here is a display of the horizontal diagram. The gain indicates that there are 2 antennas.
Here is a display of the vertical diagram of a single antenna.
Here is another view of a single 4 Element antenna.
If you want to have more background knowledge on antennas and how-to make them, you will find an ultimate resource here:
W4RNL L.B.Cebik W4RNL ultimate ANTENNA Site. A must !
Text and All Images are Copyright by Christoph Petermann DF9CY
GO (back) and visit my homepage