bedea – Rosenberger - Bedea Berkenhoff & Drebes GmbH

edea – Rosenberger
CoMeT – newsletter 01/2003
EMC - Standards
The standard to determine the electromagnetic compatibility on Communication Cables,
EN 50289-1-6 "Communication cables – Specification for test methods Part 1-6: Electrical test
methods – Electromagnetic performance" was published in 2002.
The procedure according to clause 6 of EN 50289-1-6, Transfer impedance, triaxial method as
well as the procedure according to clause 8 of EN 50289-1-6, Screening attenuation, triaxial
method can be achieved with the Test System CoMeT with one set-up in one go with simple
and easy sample preparing.
The procedure to measure the Coupling attenuation of screened balanced pairs which was
prepared by bedea, is accepted from IEC TC 46 and published as IEC/PAS 62338 Ed1.
The procedure is in IEC TC 46/WG5 under further consideration.
A new designed test set-up as accessory to the CoMeT 40 to measure the screening
attenuation of connectors and cable assemblies was introduced at the last meeting of
IEC TC 46 in December 2002 in Copenhagen.
Based on the triaxial method according to IEC 61196-1 AM1 resp. to EN 50289-1-6 the
screening attenuation of connectors and cable assemblies may be measured in the CoMeT
tube. The feeding cable of the connector or cable assembly under test is shielded by an
additional RF-tight tube which enlarges the electrical short device of a connector.
This allows to measure the screening attenuation of electrical short elements like connectors
down to lower frequencies. Further advantage is the simple and easy test set-up.
A report with the theoretical background of this new test procedure was given during the
Wroclaw EMC-symposium 2002. www.bedea.com/aktuell/Normung/emc_wroclaw.htm
Generator
tube
connector
under test
receiver
contact case
tube in tube
connecting
cable
Figure 1 – Screening attenuation of Connectors with the "Tube in Tube" procedure
A draft standard for the "Tube in Tube" procedure to be distributed to IEC SC 46A and
IEC TC 46/WG5 is under consideration.
The hardware for this measurement as complement to the CoMeT 40/2 was developed by
Rosenberger HF-Technik and will be available soon. www.rosenberger.de

New developments and accessories for the CoMeT test set-up
bedea – Rosenberger
CoMeT- newsletter - 01/2003 - S. 2
There are different improvements, complements and accessories to the CoMeT test set-up
about which we want to inform you more detailed.
Due to the modular construction, the different components or complements may be assembled
without any restriction.
1 Stretching device
When measuring the screening attenuation in the tube, the cable under test shall be centred in
the middle of the tube to avoid changes of the characteristic impedance in the second system.
This may be achieved by maintain the measurement with vertical mounted tube but with
incumber handling
With the stretching device, one can keep the sample centred in the horizontal mounted tube.
Care should be taken not to apply to high stretching forces to the screen of the sample because
this will change its characteristics.
The stretching device is equipped with a torque wrench which allows to control the stretching
force.
Figure 2 – Stretching device for the CoMeT test set-up
Supply schedule: Stretching device, 1 set of contact slices, 2,2 to 9,8 mm, torque wrench
An investigation of the influence of stretching forces to the test results of screening
measurements may be ordered from bedea.
2 Extension set for 10mm to 15mm diameter
Measuring the screening attenuation and the transfer impedance up to 15mm diameter over
screen with the CoMeT 40/2 (standard application up to 9,8mm over screen).
The additional reflection due to the enlarged case shall be taken into account when evaluating
the test results.
An investigation of the influence of additional reflections to the test results of screening
measurements may be ordered from bedea.
Supply schedule: Enlarged contact case, contact slices from 9,8mm to 14,8 mm.
bedea Berkenhoff&Drebes GmbH, Postfach 1140, D-35607 Asslar, Germany, bmund@bedea.com

edea – Rosenberger
CoMeT- newsletter - 01/2003 - S. 3
3 Complement set "high screening"
When measuring screening attenuation of > 85 dB, special care shall be taken to contact the
screen of the sample under test in the connecting case. If the contact slices don't fit close to the
screen under test or if a open slot remains in the connecting case, wrong test results may be
obtained.
The complement set "high screening" consists of a separated case which presses the contact
slices close to the screen when screwing it together. Due to the smaller gradation of the contact
slices the fitting to the screen is improved.
Measurements with the complement set "high screening" with a semi rigid cable sample
resulted in ≥ 135 dB screening attenuation up to 1 GHz and ≥ 125 dB up to 3 GHz.
sheath
contact slice
inner conductor
thread
braidt
screening case
contacting resistor
and braid
load resistance
Figure 3 – Contact case of the Complement set "high screening"
Supply schedule: 1 set contact slices with intermediate sizes of 2,55mm to9,55 mm, separated
contact case with pressing device, brass, golden and VA-steel.
4 Additional contact cases
To measure the screening attenuation of connectors and cable assemblies, the connecting case
was modified that one can connect the assembly or the connector direct to the contact case.
The mating part of the connector under test can be mounted direct to the contact case and
matched with its characteristic impedance. Figure 4 shows an example wit a F-connector.
For the measuring of cables with connectors respectively of cable assemblies different cases
with drillings for different connector systems are available, e.g. F-connector, (CATV, 75 Ohm) N-
50-system, BNC etc.
Furthermore, a contact case with feeding hole for other connector systems or threads is
available.
With the same principle also IEC- and BNC-connectors may be applied.
The different contact cases may be used also with the new "Tube in Tube" system.
bedea Berkenhoff&Drebes GmbH, Postfach 1140, D-35607 Asslar, Germany, bmund@bedea.com

edea – Rosenberger
CoMeT- newsletter - 01/2003 - S. 4
F-Connector F-feed through thread
sheath
braid
inner conductor
load resistance
screening cap
Figure 4 – Contact case for connectors.
Furthermore an enlarged contact case (10mm) is available to take in matching resistors,
e.g. the printed boards MKS 2 +2 resp. MKS 8 + 2. to match balanced data cables.
5 Angled head
Measuring the screening attenuation and the transfer impedance of cable assemblies with
angled connectors. Suitable for different connector systems, e.g. those of clause 4.
Figure 5 – Angled head
The angled head may be combined also with the new "Tube in Tube" system.
Suitable for the CoMeT 40/2.
bedea Berkenhoff&Drebes GmbH, Postfach 1140, D-35607 Asslar, Germany, bmund@bedea.com

edea – Rosenberger
CoMeT- newsletter - 01/2003 - S. 5
6 Open test head
Measuring the Coupling attenuation of screened balanced cables.
The procedure to measure the Coupling attenuation with the open head is international
standardised as IEC/PAS 62338 Ed1, Coupling attenuation, triaxial method.
Figure 6 – Open test head
7 Contact case for RJ 45 connectors
Measuring the Screening attenuation and the Coupling attenuation of balanced cable
assemblies, e.g. of Patch cables.
Figure 7 – Connecting case for RJ 45 connector
The matching resistors of the different pairs are already integrated. The mating part of the
RJ 45 connector inside the case may be changed easily.
bedea Berkenhoff&Drebes GmbH, Postfach 1140, D-35607 Asslar, Germany, bmund@bedea.com

8 Printed board MKS 2+2/8+2
bedea – Rosenberger
CoMeT- newsletter - 01/2003 - S. 6
To measure Transfer impedance, Screening attenuation and the Coupling attenuation, the
sample under test shall be matched with its characteristic impedance inside the matching case.
In case of coaxial cable this is done easily with a Mini-Melf or comparable resistor, which is
soldered between inner- and outer conductor. This task is much more difficult in case of
balanced cables with four or more pairs.
To match balanced pairs, the printed board contains two parallel mounted 50 Ohm mini
resistors with one 25 Ohm mini resistor in series. This allows to match the common mode as
well as the differential mode. The printed board is designed to fit into the contact case.
Supply schedule: 100 Boards each.
9 Control software for Windows®
The new Software is a complete rework of the former DOS-Version.
The new Control- and evaluation Software WinCoMeT is completely new designed for
MS-Windows ® NT/Windows ® 2000 respectively Windows ® XP.
bedea Berkenhoff&Drebes GmbH, Postfach 1140, D-35607 Asslar, Germany, bmund@bedea.com

edea – Rosenberger
CoMeT- newsletter - 01/2003 - S. 7
The basic version of the WinCoMeT software includes the measurements of Transfer
impedance, Screening attenuation and Transmission.
With pull down commands different types of networkanalyzers may be chosen and controlled.
With the storage procedure test results may be stored and prepared for further evaluation.
Beside multiple possibilities of the graphic representation, test results may be send to
MS-Excel ® or to MathCad ® by mouse click.
(for now as ß-version available)
Prices for all components on request.
Production of all components:
Rosenberger Hochfrequenztechnik GmbH & Co.
Postfach 1260
D - 84526 Tittmoning
www.rosenberger.de
Sales and Service:
bedea Berkenhoff & Drebes GmbH, Asslar
Contact and further information's:
Bernhard Mund
bedea Berkenhoff & Drebes GmbH
Herbornerstraße 100
D - 35614 Asslar
Germany
Tel.: +49 6441 801 133
Fax.: +49 6441 98 32 30
e-mail: bmund@bedea.com
homepage: www.bedea.com
bedea Berkenhoff&Drebes GmbH, Postfach 1140, D-35607 Asslar, Germany, bmund@bedea.com