Description

Eccosorb® MF

LOSSY, MAGNETICALLY LOADED, MACHINABLE STOCK

Eccosorb MF is a series of rigid magnetically loaded epoxy stock, which can be machined for use as absorbers, attenuators and terminations in waveguides, coaxial or stripline applications. With products such as these, it is necessary to be conversant with the dielectric and magnetic properties of the materials, which are listed in this technical bulletin, the values given are normalized with respect to free space, see Typical Electrical Properties table.

Specific product Characteristics

Features&Benefits
Rigid Machinable
Markets
Commercial Telecom Security and Defense
Typical application
Eccosorb MF is widely used as absorbers, attenuators, and terminations in waveguides and coaxial lines. It has also been successfully used as a high-Q inductor-core material in such devices as slug tuners. It is also useful in many other magnetic components. Simple RF filters can be formed by passing filament leads through small blocks of Eccosorb MF, or by casting appropriate sections of the material around such leads by using one of the electrically equivalent castable absorbers. There are also applications in antenna elements and in certain free-space absorbers. For assistance in termination design, see Termination Design Considerations.
Availability
Eccosorb MF is available in the following standard stock sizes : Sheets 30.5 cm x 30.5 cm (12” x 12”) in thicknesses of 0.32, 0.64, 0.95, 1.27, 1.59, 1.91, 2.54, 3.81, 5.08, 6.35, 7.62 cm (1/8, 1/4, 3/8, 1/2, 5/8, 3/4, 1.0, 1.5, 2.0, 2.5 & 3.0”). Rods 30.5 cm long (12”) in diameters of 0.32, 0.64, 0.95, 1.27, 1.59, 1.91, 2.54, 3.81, 5.08, 6.35, 7.62 cm. (1/8, 1/4, 3/8, 1/2, 5/8, 3/4, 1.0, 1.5, 2.0, 2.5 & 3.0” ) Bars 30.5 cm long (12”) in squares of 0.64, 0.95, 1.27, 1.59, 1.91, 2.54, 3.81, 5.08 cm (1/4, 3/8, 1/2, 5/8, 3/4, 1.0, 1.5 & 2.0”). Other sizes, shapes, thicknesses, and configurations are available on special order. In some cases, depending on which Eccosorb MF series is being used, casting of certain configurations can be done during manufacturing as shown below.
Instructions for use
The most widely used member of the Eccosorb MF series is MF-117. It is an excellent material to start experimentation. Most designs of terminating and attenuating elements depend heavily upon cut-and-try procedures. A preliminary design is established by experience or rough estimates of probably satisfactory dimensions, a piece of Eccosorb MF is machined and tested for VSWR and/or attenuation and the design is then modified as required. In coaxial, waveguide and strip-line terminations, either step-tapered or uniformly tapered configurations can be used. Step-tapered terminations are narrow-banded and highly critical dimensionally. They are recommended only where essentially single frequency operation is anticipated. Increasing the number of steps beyond two can increase the usable band-width and such designs are helpful when limited length is available in the direction of propagation. Reproducibility of the performance of step-tapered terminations may be difficult because of their sensitivity to small changes in magnetic and dielectric properties. Uniformly tapered terminations are generally preferred because of the low VSWR which is possible to achieve over a wide frequency range. Dimensions are reasonably non-critical and performance is reasonably insensitive to magnetic and dielectric properties. In general, the more gradual the taper, the lower the VSWR. A length-to-base-width ratio of 10:1 is highly desirable for VSWR as low as 1.01 over a full waveguide frequency band, particularly with materials having the higher values of M’ and K’. A sufficiently long taper must be used so that very little energy reaches the base mounting plate where it can be reflected back into the line. The one-way attenuation should be at least 25 dB for VSWR as low as 1.01. Wall-type uniform tapers offer maximum heat-transfer efficiency and are recommended for high-power applications.
Related products
For higher temperature applications up to 260 °C, refer to the electrical equivalent Eccosorb® MF500F.

Product properties

Properties	ECCOSORB MF
Frequency Range	>1 GHz
Service Temperature °C (°F)	<180 (<356)
Density g/cc	1.6 – 4.9
Hardness, Shore D	85
Tensile Strength (MPa)	55
Thermal Expansion per °C	~30 x 10^-6
Water Absorption, % 24 hours	<0.3
Thermal Conductivity W/mK	1.44

Data for design engineer guidance only. Observed performance varies in application.
Engineers are reminded to test the material in application.

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