ETS-Lindgren 3140B Hybrid Log Periodic and Bowtie (BiConiLog) - Manual (Page 34)

Model 3140B Typical Antenna Factors
This graph illustrates the typical horizontal antenna factors for the
Model 3140B in the frequency range 26 MHz to 3000 MHz.
The separation distance for the ANSI C63.5 three and 10 meter
calibrations is measured from the antenna midpoint, while for
SAE/ARP-958 one meter calibrations the distance is measured from
the antenna tip. Midpoint is defined as half the distance between the
small elements and the bow ties, which is about 65 cm from the small
end tip.
34 | Typical Data