It might be enlightening to Google the G5RV antenna...
The design by Lou Varney, G5RV first appeared in the RSGB Bulletin
and was designed as a 20M -->ONLY<-- antenna, with a specific combination
of open wire and coax lengths. (I have a copy of the original article.)
As I often say … There's nothing new in antennas since the '30's ... only
the names, usually for "marketing" reasons. Even the common "J-pole" is a
"Zep", only (usually) mounted vertically.