How to turn your boom into an effective antenna for 40 or 30 meters. by K4RO

I have tried several different antennas for the 40 meter amateur band, usually with less-than-optimum results. After trying different dipoles, wire arrays, and verticals, I have found that loading the boom of my high tribander gives me by far the best bang for the buck. For the cost of a feedline and a few capacitors, I have a rotatable dipole at 100' which outperforms all other 40 meter antennas I've tried here.



Matching the boom of a large tribander for 40 meters was not my idea. I got the idea from AA4NU, who got it from N4KG. Tom's description of the theory can be found at the following link: http://lists.contesting.com/archives//html/Towertalk/2002-03/msg00731.html

My first attempt used capacitors which were too small. The enclosure was also not suited to the task.



For the new unit, I chose to stick with air variable capacitors for ease of tuning. Hopefully the new caps and better enclosure will last for a few contest seasons. The bandwidth is about 110 kHz. This is more than enough to cover the 40 meter CW band.



Note that this technique can only be used for antennas which have their end elements grounded to the boom. Force 12 and Skyhawk antennas will probably not work, as there is no end loading on the boom.



Following are a few pictures of my attempts at building an effective

omega match for my top PRO-57A antenna.



Give this a try. I think you'll be impressed with the results!