Good morning, John.
Yes, we have tried this in several combinations. From the practical side, a
second reflector does not significantly add to the F/B to warrant the extra
mechanical and cost factors. At UHF, maybe it would be worth it. At HF,
it is surely not to be considered in a horizontal Yagi! With the modeling
software, this can be achieved by re-tuning the design, with a focus on F/B.
One other item is that most folks are looking for forward gain and adding an
element to possibly improve F/B is not very attractive. Oh -- if the second
reflector is located on the boom, behind the first reflector, it has very
little value, as the first reflector contains the majority of the current
and the second one has little to work with.
Vertical arrays are another situaiton. We actually make a vertical dipole
array using a single driver and two reflectors in somewhat of a triangle
layout. The array has an exceptional F/B and a very wide front lobe. We are
now experimenting with it using a trio of our ZR-3 20-15-10 mtr 5 1/2' tall
verticals! It seems like it will make a nice, directional array with forward
gain, while being about even with the typical fence line level. We'll ahve
to see.
Please let us know if we can add anything more for you.
Have a good day and 73,
Tom, N6BT
Force 12 Antennas and Systems
(Home Page http://www.QTH.com/force12 )
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