ETS Lindgren 3140 User Manual

Model 3140

™

BiConiLog

MANUAL

Antenna

© EMC TEST SYSTEMS, L.P. – MARCH 2002 REV C – PN 399258

MODEL 3140 BICONILOG ™ ANTENNA

EMC Test Systems, L.P. reserves the right to make changes to any product described herein in order to
improve function, design or for any other reason. Nothing contained herein shall constitute EMC Test
Systems, L.P. assuming any liability whatsoever arising out of the application or use of any product or
circuit described herein. EMC Test Systems, L.P. does not convey any license under its patent rights or the
rights of others.

© Copyright 2002 by EMC Test Systems, L.P. All Rights Reserved.

No part of this document may be copied by any means

without written permission from EMC Test Systems, L.P.

E-MAIL & INTERNET

[e-mail]
http://www.ets-lindgren.com

USA

1301 Arrow Point Dr., Cedar Park, TX 78613
P.O. Box 80589, Austin, TX 78708-0589
Tel [phone] Fax [phone]

FINLAND

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Mekannikontie 1
27510, Eura, Finland
Tel [phone]
Fax [phone]

SINGAPORE

Lindgren RF Enclosures Asia-Pacific
87 Beach Road
#06-02 Chye Sing Building
Singapore 189695
Tel [phone] Fax [phone]

© EMC TEST SYSTEMS, L.P. – MARCH 2002
REV C – PN 399258

MODEL 3140 BICONILOG™ ANTENNA

INTRODUCTION............................................................................................................ 1

ASSEMBLY INSTRUCTIONS ......................................................................................4

MOUNTING INSTRUCTIONS ..................................................................................... 8

APPLICATION.............................................................................................................. 12

TYPICAL DATA ...........................................................................................................14

SPECIFICATIONS........................................................................................................ 18

MAINTENANCE........................................................................................................... 19

WARRANTY STATEMENT........................................................................................ 20

Table of Contents

© EMC TEST SYSTEMS, L.P. – MARCH 2002
REV C – PN 399258

MODEL 3140 BICONILOG ™ ANTENNA

© EMC TEST SYSTEMS, L.P. – MARCH 2002
REV C – PN 399258

MODEL 3140 BICONILOG™ ANTENNA Introduction

INTRODUCTION

The ETS-Lindgren EMCO brand Model 3140 is a high­field addition to the popular bow-tie/log periodic
combination BiConiLogTM family, providing the highest
field-to-power ratio at low frequencies of any of the
BiConiLog™ antennas. The Model 3140 is designed
specifically to generate the field levels required for
immunity/susceptibility tests required by standards such as
IEC/EN 61000-4-3 using the lowest amount of input power
possible.

A BiConiLog™ antenna combines a broadband biconical­like 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
MHz. 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 segment
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

© EMC TEST SYSTEMS, L.P. – MARCH 2002 1
REV C – PN 399258

Introduction MODEL 3140 BICONILOG™ ANTENNA

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
bow-tie. A simple wire outline bow-tie antenna is
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
elements. 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 2.8 m

tuned 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 T
end.

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

2 © EMC TEST SYSTEMS, L.P. – MARCH 2002

REV C – PN 399258

MODEL 3140 BICONILOG™ ANTENNA Introduction

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 1
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 is
directional.

The antenna has dual mounting bracket and 1/4x20 UNC
knob for attaching to ETS-Lindgren tripod and tower
adapters. The brackets are spaced to align with the
mounting holes on the Model 7-TR tripod and the ETS­Lindgren towers. Typical antenna factor data is included in
Figure 11.

Note: The Model 3140 is designed only for immunity
testing. The large size of the antenna makes it impractical
for emissions testing where height scanning is required,
and the bow-tie end plates increase the measurement
uncertainty when the antenna is polarized vertically. Thus,
individual calibrations are not provided for the Model

3140.

© EMC TEST SYSTEMS, L.P. – MARCH 2002 3
REV C – PN 399258

Assembly Instructions MODEL 3140 BICONILOG™ ANTENNA

ASSEMBLY INSTRUCTIONS

The Model 3140 Antenna consists of the following
(shipped unassembled):
1 ea. Boom Assembly

2 ea. Bow-tie Elements
2 ea. Long T leg Elements
2 ea. V Elements
4 ea. Diagonal Struts
2 ea. Boom adapters for ETS booms with 7/8” mount holes
2 ea. Thread inserts 7/8” to ¼”

Step 1. Attach a bow-tie element to the antenna balun box (see

Figure 1). The bow-tie should be standing vertical and the
antenna held horizontal and attached to it using the hand
screw knob. Supporting the antenna during the assembly
process will eliminate stress at the connection of the balun
box and prevent damage to the connection.

FIGURE 1 – Assembly Step 1

4 © EMC TEST SYSTEMS, L.P. – MARCH 2002

REV C – PN 399258