Appendix E
115
Ferrite absorber specifications
The absorbers described in these installation recommendations are made from a low-grade
ferrite material which has high losses at radio frequencies. They therefore act like a high
impedance in this waveband.
The recommended components are produced by Parker Chomerics (617-935-04850) and are
suitable for use with cable having an outside diameter up to 10—13mm. The specification is
as follows:
Chomerics part number 83-10-M248-1000 83-10-A637-1000
Outside diameter 17.5mm 28.5mm
Inside diameter 10.7mm 13.77mm
Length 28.5mm 28.57mm
Impedance at 25MHz 80Ω 135Ω
Impedance at 100MHz 120Ω 210Ω
Curie temperature 130°C 130°C
(the device should not be operated near this temperature)
Handling and installing the ferrite absorbers
Take care when handling the absorbers - they can shatter if dropped on a hard surface. For this
reason the suggested method of installation is to use a short length of 19mm diameter heat-
shrink sleeving (See figure 1). This gives a degree of physical protection while the cable is
being installed. The sleeving should have a shrink ratio of at least 2.5:1. Cable ties may be
used as an alternative, however they give no physical protection to the absorber.
Ferrite absorber
retained by
heatshrink sleeving
Figure 1 - Ferrite Sleeve Installation
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