ETS-Lindgren 3140B Hybrid Log Periodic and Bowtie (BiConiLog) - Manual (Page 31)

6.0 Application
After mounting the Model 3140B BiConiLog TM , connect an N-type coaxial cable
from the antenna connector to a signal generator or amplifier. Contact with any
metal or non-metallic structure can capacitively load the antenna, which may
cause unrepeatable results. Therefore, make sure that no part of the dipole
elements or bow ties is in contact with the tripod or tower, particularly in
vertically-polarized tests. Where possible, run the feed cable straight back at
least one meter or more from the Model 3140B before dropping vertically.
Both horizontal and vertical polarizations are easily accomplished when the
Model 3140B is mounted on an ETS-Lindgren tower. The Model 7-TR Tripod
Positioner is designed specifically for T bow tie BiConiLog antennas for easy
changes to polarization, and with the air polarization option can provide
automated polarization using a Model 2090 Multi-Device Controller. See
Mounting Instructions on page 23 for mounting schemes for ETS-Lindgren
towers and the 7-TR Tripod.
For immunity testing, the electric field strength generated at a distance d can be
approximated by:
( )
E
Pg
d
V / m
=
30
d = distance, in meters
g = numeric gain (10
G[dB]/10
)
P = antenna net input power, in watts
An estimate of the power required for any field strength E can be obtained from
the forward power graphs in Typical Data on page 33, which shows forward
power required in watts to generate 1 V/m. While the formula provided previously
is based on the net power (forward minus reflected) transmitted by the antenna,
the gain determined from the antenna factor already contains effects due to
mismatch, so the formula then predicts the required forward power rather than
net power. To determine the power (in watts) required for any other field strength
not shown, multiply the power required for 1 V/m by the desired E-field squared,
or
Application | 31