ETS-Lindgren 3147 Log Periodic Dipole Array Antenna - Manual (Page 8)

Because the radome is almost RF-invisible, it has very little effect on the
performance of the Model 3147 (see VSWR on page 23).
The base of the Model 3147 accepts an ETS-Lindgren or other tripod mount with
1/4–20 threads. Additionally, the antenna is shipped with a support rod. A variety
of mounting options are available for the Model 3147. For information, see
Mounting Instructions on page 15.
Regarding Calibration of Log Periodic Dipole Antennas
To meet the requirements of two different specifications, this log periodic dipole
antenna was calibrated at two different spacings.
• SAE ARP 958 (Society of Automotive Engineers, Aerospace
Recommended Practice) requires an antenna spacing of one meter,
measured tip to tip.
• ANSI 63.5 requires a spacing of three and ten meters measured from
the projection onto the ground plane of the midpoint of the longitudinal
axis of the antenna.
The ARP and the ANSI requirements disagree because these standards were
written for different purposes. Therefore, when calibrating the log periodic array
antennas per ARP 958, ETS-Lindgren measures from tip to tip and sets the
spacing to one meter. When calibrating the log periodic array antennas per
ANSI C63.5, ETS-Lindgren measures from the midpoint to the midpoint of the log
periodic antennas for 3-meter and 10-meter calibrations.
It is important in compliance demonstration testing to measure the
spacing from the antenna to the Equipment Under Test (EUT) as it
was measured when calibration was performed.
For additional information, contact ETS-Lindgren.
8 | Introduction