ETS-Lindgren 3148B Log Periodic Dipole Array - Manual (Page 24)

24 | Application
Operation
After mounting the Model 3148B onto an ETS-Lindgren tripod or antenna mast
adapter, connect an N-type coaxial cable from the antenna connector to a
generator (immunity) or receiver (emissions). Both horizontal and vertical
polarizations are easily accomplished when the Model 3148B is mounted onto a
tower or tripod. Contact with any metallic or non-metallic structure can
capacitively load the antenna, which may cause inconsistent results. Therefore,
care must be taken to ensure that no part of the dipole elements is in contact with
the tripod or tower, particularly in vertically-polarized tests. Where possible, run
the feed cable straight at least one meter or more back from the Model 3148B
before dropping vertically.
For emissions measurements, electric field strength in db[V/m] is obtained from:
E(dBV/m)=V(dBV)+AF(dB1/m)+ α(dB)
V = the receiver or spectrum analyzer voltage reading
AF = antenna factor
α = cable loss in dB, if cable losses are non-negligible
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