MIL-DTL-25879G
3.2 Design and construction. The RF transmission switch SA-521A/A shall be designed to operate as a
single-pole double-throw coaxial switch. When the switch is de-energized, the internal RF connection shall return to
a normally closed condition with the common terminal connected to terminal number 2. Separate functions shall be
provided to permit both outputs to be connected to the common terminal at once and for both outputs to be
disconnected at once when specially energized. The switch shall employ make-before-break contact arrangements
for switching from position 1 to position 2, and from position 2 to position 1.
3.2.1 Drawings and procedures. The original design and construction drawings and production procedures as
approved by first article testing shall remain available for the inspection by the cognizant government inspector. No
changes or waivers shall be allowed without approval of the acquiring activity (see 6.3).
3.2.2 General. Any military specification, standard, or handbook referred to in this specification may be replaced
by an equivalent commercial standard as determined by the acquiring activity (see 6.3).
3.2.3 Frequency. The RF switch shall be designed to operate at any frequency up to and including 1.250 GHz.
3.2.4 Nominal impedance. Nominal impedance of the switch shall be 50 Ω.
3.2.5 Mounting provisions. The RF switch shall mate with mounting MT-1995/A (see MIL-DTL-32054). Positive
electrical continuity between the switch unit and the individual fasteners shall be assured.
3.2.6 Connectors.
3.2.6.1 Power connector. The power connector shall be sealed, and shall mate with connector MS3456L10SL3S.
The pin arrangement shall be as follows:
a.
When pins A and C are connected to a 28 V dc source, the switch shall present a parallel connection of
both outputs to the input.
b.
When pins B and C are connected to a 28 V dc source, the switch shall present an open circuit between
both outputs and the input.
c.
When pins A and B are parallel and connected with pin C to a 28 V dc source, the switch shall change over
from antenna number 2 position to antenna number 1 position.
d.
When the switch is de-energized, the input shall be connected to antenna 2.
e.
Pin C shall be considered to be the common terminal and shall not be grounded internally.
3.2.6.2 RF connectors. The RF switch shall be equipped with a receptacle connector meeting the mating
dimensions of MIL-PRF-39012/2 to mate with "N" series connector (M39012/01-0002 or M39012/01-0005) in
accordance with MIL-PRF-39012/1. The input shall be labeled "IN"; the outputs shall be labeled as shown on figure
1.
3.2.6.3 Connector caps. All connectors shall be supplied with push-on caps to prevent connector damage and the
entrance of moisture and foreign material during storage.
3.2.7 RF contact construction. The RF contacts of the switch shall be constructed to provide a wiping action
during operation.
3.2.9 Retention devices. All screws and other hardware shall be adequately equipped with retaining devices to
prevent loosening from vibration or shock over the life of the switch.
3.2.10 RF interference. RF interference control requirements shall be in accordance with MIL-STD-461.
3.2.11 Weight. The weight of the switch shall not exceed 1 pound.
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