ETS-Lindgren 3127 Magnetic Dipole Antenna - Manual (Page 14)

14 Operation www.ets-lindgren.com
Ferrite loaded RF cables are recommended for use with the Model 3127 to
minimize the interaction with the loop. ETS-Lindgren offers a line of ferrite loaded
cables for this application. Lightweight RF cabling should be used and properly
supported to avoid putting unnecessary load on the SMA connector of the
antenna. Route cabling away from the antenna along the antenna axis as far as
practical to minimize the interaction of the cable with the antenna, and to avoid
distortion of the antenna pattern.
Operational Considerations
For the purpose of ripple test measurements, the loop may normally be used
without any additional considerations. However, should large standing wave
effects be noticed, it is recommended that a 3 to 10 dB pad/attenuator be used at
the input end of the antenna to minimize standing waves on the transmit cable.
The magnetic field of the antenna is polarized perpendicular to the antenna axis.
The specified symmetry is realized along the plane perpendicular to the antenna
axis and centered at the location of the loop element. The location of the loop
(bore sight location) is indicated by the centerline of the plastic radome covering
the antenna, approximately 15 cm (5.9 inches) from the base, connector end, of
the antenna mounting.
It is required that a 10dB pad/attenuator be used at the input end of the antenna
to minimize standing waves on the transmit cable. This is especially important for
frequencies where the input VSWR is greater than 1.2:1.