8 May 2014

Small 2m beam or a pair of stacked big wheels?

At the moment I am enjoying 2m and 70cm horizontal using a small yagi with 3 elements on 2m and 5 elements on 70cm. Both sets of elements are on the same boom and fed with a single 17m length of Westflex low-loss coax. Last Tuesday was the first chance to try the beam in a 2m contest. Although I have still to try the beam in a 70cm contest, I am wondering about 2 stacked big-wheels just for 2m.

A pair of big wheels are reported to have a horizontal gain of around 5dBd, which is comparable to the gain of my 3el beam, but without the necessity to rotate the antenna. In a 2m UKAC contest this arrangement may well be better? With the beam I was constantly wanting to adjust the beam direction. On my little halo (and big-wheel) I'd  have no choice.

For now, I shall stick with the dual-band beam, but I would be interested to hear your views on big wheels as gainy 2m horizontal antennas. I could probably mount the big-wheels slightly higher too.

Unlike many, I am not so keen that I want huge beams and high power. My interests are beacon hunting and casual contesting. In the last UKAC 2m contest I ran 5W.

1 comment:

Anonymous said...

Big wheels are tricky, the active part is the three arcs, the six spokes are overcoupled and interact strongly. Although you do get gain it is not an easy matter to obtain the potential.
There are more stable ways of getting the performance, three center fed dipoles at 120 degrees will do it without the stability issues of the big wheel which is a pig to optimize. (the difficulty of getting wheels to work WELL - as opposed to just look big-is perhaps the reason why so few are in use after all the years they have been around.)

There are quite a few other omni options, a Vee or M shaped dipole can be quite circular and will stack easily. Good subject for antenna modeling software! weeks of fun!

Alan G8LCO