ETS Lindgren 3140 Antenna
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The ETS-Lindgren Emco
brand Model 3140 is a high-
field addition to the popular bow-tie/log periodic
combination BiConiLog family, providing the highest
field-to-power ratio at low frequencies of any of the
The Model 3140 is designed specifically to generate the
field levels required for immunity/susceptibility tests
required by standards such IEC/EN 61000-4-3 using the lowest
amount of input power possible.
A BiConiLog Antenna
combines a broadband biconical-
like bow-tie Antenna
with a standard LPDA (log periodic
dipole array) to replace the traditional use of two antennas
in the 26-1000 MHz EMC test frequency range. Many
EMC antennas are variations of a standard tuned dipole,
which must be nearly half a wavelength long to transmit or
receive energy most efficiently. Thus, at 26 MHz, a tuned
dipole would have to be approximately 5.3 meters long,
about 4.6 meters long at 30 MHz, and 2.8 meters long at 50
Unfortunately, this is too unwieldy for many
anechoic chambers and test sites. The end plates of the
Model 3140 T bow-ties make the bow-tie Antenna
look like an Antenna
twice as long as its 1.6 meter length.
The result is about a 10-dB improvement in low frequency
transmit gain compared to a same-length regular bow-tie.
Although bow-ties have been used for all of the elements
on some log-periodic Antenna
designs in the past, in EMC
applications the advantage gained is an extension of the
useful low frequency range of the typical LPDA's from
100 MHz down to 26 MHz. At 26 MHz, an efficient single
dipole type Antenna
must be over 5 meters long, whereas
suitable performance is obtained here with a 1.6 meter long
A simple wire outline bow-tie Antenna
narrowband compared to
a sheet bow-tie or biconical, thus
struts are added to the Model 3140 bow-ties to better
simulate the broadband sheet bow-tie.
The unique feature of the Model 3140 is the T bow-tie
A T bow-tie increases the equivalent dipole
electrical length, thereby decreasing resonant frequency
and increasing efficiency in the 20-60 MHz range.
Similarly, a regular bow-tie has a lower resonant frequency
than an equal length single-wire dipole. The T bow-tie has
its first resonance at a frequency where its length is about
0.22λ, a regular bow-tie at a length of 0.3λ, and a tuned
dipole at about a length of 0.48λ. Thus at 50 MHz the 1.4
m long T bow-tie of the Model 3140 behaves like a 2.8tuned
dipole. Cross-polar radiation is minimized because
current flow on one of the T end frames is almost exactly
cancelled by the oppositely-phased current on the other
The standard "self-balun" feed of the log-periodic also
provides a matched balanced feed to the bow-tie elements.
To prevent cable pickup below 100 MHz, and to improve
matching to the bow-tie elements, the Model 3140 contains
a "balun" transformer which acts as a common-mode choke
to keep unbalanced current off the coaxial feed cable outer
shield, as well as adding some additional inductance to
improve impedance matching to the bow-ties. Even though
the Model 3140 is highly balanced (symmetry +/- 0.5 dB),
in vertically polarized measurements cable position can
effect results, so it is recommended that the cable be
suspended horizontally back from the Antenna
at least meter
before any vertical drop. Below 150 MHz, bow-tie
radiation dominates with a dipole-like pattern, while above
150 MHz the radiation in the plane of the elements directional.
has dual mounting bracket and 1/4x20 UNC
knob for attaching to ETS-Lindgren tripod and tower
2.70 Mbytes (2834556 Bytes)
01 March 2002
Electronic document, no scan, very well readable.
25 December 2017
INTRODUCTION ... ASSEMBLY
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