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Amplifiers (Continued)


Instrumentation Amplifier

The RF Depot 8895 and 8896 series of power amplifiers consist of a solid state microwave amplifier module mounted with a power supply and appropriate accessories in an aluminum chassis. The chassis includes a cooling fan that is DC powered to provide universal AC mains input capability.

Available options include continuously variable attenuators (0-20 dB) on the input or the output, or at both the input and the output. Other options include a rack mount kit and cover, slides, and a circular threaded power line connector.

Since the emphasis of the 8895 and 8896 series is to provide maximum linear RF power, the output of the microwave amplifier is connected as directly as possible to the output of the unit. In units below 2 GHz, the amplifier output connector is directly available at the output of units without output attenuators.

The chassis is fully welded aluminum enclosure that accepts rack slides and rack mounting "ears" or a bench cover and feet. Rack mounting can be accomplished without the use of sides through the use of rack mounting "ears." These mounting angles are stored within the chassis when delivered as a bench mounted unit. The bench cover is removed and discarded. The rack cover (supplied within all bench mounted units) is removed and the mounting angles are removed from within and mounted on the outside of the chassis. The rack cover should be reinstalled to provide maximum protection to the equipment. Since these items add 3.6 lbs to the weight of a bench unit and are sometimes discarded by field personnel, spare or additional rack covers and rack mounting hardware are separately available. Option 21 deletes these items on the original order.

Mounting points for rack slides with captive hardware are provided as standard items on all units. The rack mounting angles also mount using captive hardware.

Access to the components is obtained by removing the top cover in a rack mounted configuration, and by removing the bench cover in a bench configuration. The rack cover uses captive turn fasteners. The bench mount cover uses standard stainless steel fasteners.

The equipment enclosure provides protection from mechanical shock and falling water particles in both the bench and rack mounted configuration. Ventilation openings are on the sides and rear of the chassis. This design and construction meets the requirements of MIL-T-28800C for style E enclosures in both configurations. MIL-T-28800C style T transit cases are available on special order.

The power supplies are contained on a separate subassembly chassis and are field replaceable using standard electronic tools.

The RF DEPOT series 8895 and 8896 amplifiers are all mounted within a six sided welded aluminum chassis. One side of the chassis consists of a mounting flange with captive hardware that accepts a cover. The chassis normally includes a 28 volt DC fan, a power switch, a standby switch, two fuses (both sides of the utility power main are fused), two pilot lights (1 for full operation and 1 for standby fan operation), coaxial cables, and a power supply. Amplifiers that require DC voltages other than 28 VDC, or require dual voltages are equipped with two power supplies.

The power supplies use linear series regulators and are contained in a separate sub-assembly for easy field replacement and maintenance.

Below 2 GHz, the microwave amplifiers use hermetically sealed semiconductors enclosed within a well shielded case. The DC feed for the amplifier is filtered at the amplifier case. Most frequency ranges above 2 GHz use a welded hermetically sealed amplifier case. The amplifier cases are aluminum or stainless steel to provide maximum corrosion protection. Epoxy adhesives are not used as hermetic seals due to their preponderance to "breathe" during the temperature cycling that takes place in normal transit. Transistors used are of domestic US manufacture and use gold metalization to provide long and reliable service life.

These amplifier assemblies are constructed in a welded aluminum chassis, with a chromate conversion (iridite) finish using stainless steel fasteners. Internal coaxial cables are 0.141 inch diameter tin plated semi-rigid with SMA connectors to provide good RF shielding. Units can be provided with EMI power line filters and closure gaskets on special order. Such measures are not necessary however since the power supply provides approximately 50 dB of decoupling between the DC output and the AC input, and the RF filtering on the amplifier case provides another 50 dB of decoupling between the DC output and the AC input, and the RF filtering on the amplifier case provides another 50 dB or more isolation at 1 GHz and above.

Standard units have a DC fan to provide forced air cooling. All units have a "standby" mode that allows the fan to operate without the microwave amplifier module to provide a "cool down" mode when used in an extremely hot environment. This power switch also allows the "turn off" of the RF signal by turning off the amplifier module only. The DC fan minimizes generation of any possible EMI, and allows universal utility mains input. Waveguide vents can be supplied on special order and are normally installed on each side and on the rear panel. Waveguide vents should be included with EMI closure gaskets if high level RF shielding is desired.

Type N coaxial connectors are standard. Type SMA can be provided at no additional cost. Add suffix M/M to the unit part number for SMA connectors.

A detachable power cordset with a standard IEC receptacle is standard. A four position voltage selector card (100, 110, 220, 240 volts) is contained within the IEC 320/CEE-22 power entry module on the rear panel. For operator safety, the fuses and voltage selector card cannot be accessed when the cordset is secured in the IEC connector. A fixed circular connector (option 24) is available when desired. Power supplies are sized for operation from 50 Hz to 400 Hz.

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