MIL-DTL-28791C
3. REQUIREMENTS
3.1 Specification sheets. The individual item requirements shall be as specified herein and in accordance with the
applicable specification sheet. In the event of any conflict between requirements of this specification and the
specification sheet, the latter shall govern.
3.2 First article inspection. Products furnished under this specification shall be products which have passed the
first article inspection in 4.4.
3.3 Materials. The materials shall be as specified herein; however, when a definite material is not specified, a
material shall be used which will enable the isolators and the circulators to meet the performance requirements of this
specification. Acceptance or approval of any constituent material shall not be construed as a guaranty of the
acceptance of the finished product.
3.3.1 Copper alloy. Copper alloy used in the fabrication of waveguide-type isolators and circulators shall conform
to commercial bronze, 90 percent, of ASTM-B372. Copper alloy used in the fabrication of coaxial-type isolators shall
conform to the material requirements of ASTM-B372, 99.90 percent purity.
3.3.2 Aluminum alloy. Aluminum alloy shall conform to the requirements for 6061 or 6063 of ASTM-B210. The
finished waveguide shall have an "F" temper and after heat treatment and aging, shall meet the mechanical
properties of the T6 temper of ASTM-B210.
3.3.3 Rubber. Rubber shall conform to the requirements in A-A-59588.
3.3.4 Pure tin. The use of pure tin, as an underplate or final finish, is prohibited both internally and externally. Tin
content of radio-frequency isolator and circulator components and solder shall not exceed 97 percent, by mass. Tin
shall be alloyed with a minimum of 3 percent lead, by mass (see 6.6).
3.4 Design and construction. Isolators and circulators shall be designed and constructed to conform to the
requirements specified (see 3.1), in a manner entirely suitable for their intended use. They shall be of the lightest
practicable weight consistent with the strength required for sturdiness, safety, and reliability. Isolators and circulators
shall be fully shielded to external magnetic fields.
3.4.1 Waveguide isolators and circulators. The mating face of the isolators or of the circulators shall be so
designed and manufactured as to provide the mating characteristics of the flange specified (see 3.1) in accordance
with MIL-DTL-3922.
3.4.2 Coaxial isolators and circulators. Connectors shall be as specified (see 3.1). The material and gauging for
receptacle connectors shall conform to the requirements of MIL-PRF-39012.
3.4.3 Dimensions. The dimensions shall be as specified (see 3.1).
3.4.4 External finish. External finish shall be applied to the isolators and to the circulators regardless of plating or
chemical treatment, except that the mating surfaces shall not be coated. The primer coat shall be zinc chromate
conforming to TT-P-645. Two finish coats of enamel, conforming to type III, class 2, of MIL-DTL-15090, shall be
applied. External coatings shall be applied as continuous films.
3.4.5 Dissimilar metals. Dissimilar metals between which an electromotive couple may exist shall not be placed in
contact with each other. Refer to MIL-DTL-14072 for the definition of dissimilar metals.
3.4.6 Screw threads. Screw threads shall be in accordance with FED-STD-H28. If used, helical inserts shall be
selected (for information refer to MIL-HDBK-454, Guideline 12).
3.4.7 Engineering parameters. The parameters of nominal impedance, voltage rating, frequency range,
temperature range, and power rating shall be as specified (see 3.1).
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