What a WASTE OF METAL....he SAYS it's a "DB-4", but Bowtie-Bowtie Separation is only 5.25-in with 7-in Whiskers, which is closer to the U-Tube "DEFECT" 4-Bay. A REAL DB-4 measures out as just under 8-in Separation with just over 6-in Whiskers:
http://imageevent.com/holl_ands/multibay/4bay
http://imageevent.com/holl_ands/multibay/4bayrefl
BOTH of these antennas are ill suited for the NEW UHF BAND, providing very low Gain on lower channels and Excessive SWR.
Note that the suggested design doesn't appear to even use the DB-4's Reflector....thereby throwing away 3 dB of Gain, which letting in Multipath and Noise from the rearward directions...
Since the Impedance is very low on lower channels and very high on higher channels, simply "shorting together" all four Antennas to a common Feedpoint will result in extremely low impedance on lower channels and MAYBE an acceptable SWR on the higher channels....but only modeling will reveal the actual performance... [PS: I'm not volunteering for this fool's errand.....]
HDTVPrimer 16-Bay and 32-Bay Antennas use a 2-Way and a 4-Way RF Splitter/Combiner respectively, thereby avoiding the interconnect Harness Hassle (NOT an easy process). AND they use the larger CM4228 Antennas, which come with a Horizontal Harness between each set of 4-Bays (such as it is). A pair of equal-length transmission lines (parallel wires) could then be used to interconnect the Vertically Stacked 8-Bays, as I have modeled and Optimized for several Vertically Stacked 4-Bays.
However, using an array of antennas actually DESIGNED for the NEW UHF Band, such as M4, FF4 or A-D DB-8e would be even better....