Microwave Converter

Model 11793A

Service Sheets 1 and 2 (Input Signal Down-Converter)

A single input on the rear panel: the FREQ OFFSET INPUT, has three logic states which control both the switching of the RF two paths, and the insertion of the optional LO Amplifier. The Level Comparator senses the three states and drives the appropriate switches.

Service Sheets 1 and 2 are the schematic diagrams of the RF circuitry of the Microwave Converter. Service Sheet 1 (SS1) documents the standard Microwave Converter (without the LO Amplifier option), and Service Sheet 2 (SS2) documents the Microwave Converter with the LO Amplifier.

The operation of the RF components is discussed in the principles of operation for the Simplified Block Diagram above. Note that the RF switches (SI and S2), shown in the schematic, automatically interrupt the current flowing into the energized solenoid once the plunger switches the RF contacts. The plungers latch via permanent magnets.

Service Sheet 3 (AI Switch Control Assembly)

The Level Comparator (UIA and U1B) and Decoder (U3A, U3B, and U3C) decode a three level input (through the rear-panel FREQ OFFSET INPUT connector) into binary levels that control the RF switches (see SS1 and SS2). The AND gates (U2) are simply open-collector inverters,'which drive the transistors (42, 43, 44, QS) to switch on and energize the solenoids of the RF switches. Table 9 summarizes the decoding.

RF

LO

Level at

U1A

U1B

U3A

U3B

 

 

 

 

 

FREQ

PinU3C8

Q2

Q3

Q4

Q5

Path

Amp

OFFSET

Pin

1

Pin

6

Pin 3

Pin

6

 

 

INPUT

 

 

 

 

 

 

 

 

 

 

 

 

Direct

out

<2.0v

H

 

L

 

H

H

 

L

Off

Off

On

On

Down-Convert

In

2.0 to 3 . w

H

 

H

 

L

L

 

H

On

On

Off

Off

Down-Convert

Out

>3.av

L

 

H

 

H

L

 

L

Off

On

Off

On

The power supplies used are:

mThe unregulated +26V supplies drive current to the RF switch solenoids, and is the input to the +12V Regulator.

8The regulated +12V is the only adjustable supply. It is the current input to the +SV Regulator as well as the reference from which both the Level comparator references are derived, and the RF Amplifiers are powered.

eThe regulated +SV supplies current to most logic devices.

Either the +26 or +12V supply can trigger the Over-Voltage Protection should the respective voltage exceed +42 or +12V. LED DS 1 gives an indication that the supply is nominally operational.

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