The UHF section is a simple UHF Yagi structure with a parasitic element that is probably there to flatten the bandwidth.
The VHF section, is not a Yagi as the two rear most elements are connected to each other with phasing lines which excludes that section from being a conventional Yagi but is rather a log-periodic design. The two long elements clipped to the underside of the boom are probably there for the same reason as the parasitic element on the UHF side.
I haven't tried modelling the antenna (not my cup of tea) but I did test it on my backyard antenna test range late last summer and compared it to several other antennas. Might have to dig out those spreadsheets and see what things look like.
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