Stacked Rhombics at TF4M.

I have finished the task of building a lower Rhombic towards the US.   The lower Rhombic is a two wire design at approximately 50 feet.   It has a fixed termination, whereas the three wire upper rhombic is switchable.

Due to my accident, the task has taken me approximately one year to finish.

The two Rhombics can be phased together with an ArraySolutions StackMatch located near the shack and by switching the upper rhombic it is possible to beam in opposite directions simultaneously.

The total amount of wire in the Stacked Rhombics is 24,300 feet (8100 meters).   This includes the amount of wire consumed by the two 3,000′ long open feeders going out to the site.

Depending on how the stacking works out, I may elect to feed the two rhombics with a 4 wire open feedline (already in place) and a 300 ohm Balun, rather than with two 600 ohm open feeders as is currently the case.  This should give me a few additional dBs in signal strength due to reduced feeder losses.

According to LaPort, the effect of stacking the rhombics is mainly to reduce the number of sidelobes with a more powerful main lobe.  The effect might therefore be a reduction in signal strength for stations off the main beam.

Initial testing is very gratifying, the lower rhombic is even quieter than the upper rhombic,  but I suspect the new antenna will mostly find it’s use in contests where it can be operated independently of the other antenna using bandpass filters, of course.