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The HP 8445B Automatic Preselector is a YIG tuned filter for use with the Spectrum Analyser HP 8555A RF Section (10MHz to 18GHz). The Preselector can be tuned exactly to the Analyser's reception frequency and eliminates harmonic mixing image and multiple responses from 1.8GHz to 18GHz. Below 1.8GHz the image and multiple responses are eliminated by a low-pass filter.

The basic cost was $2,825 in 1977. Option 002 added manual controls for $80 and option 003 added a digital frequency readout for $670. With these 2 options, this unit cost $3,575. The Manual was available for download.
Front view with Options 002 and 003
The front panel has N-type connectors for input and output. Option 002 added Auto, Manual, Low-Pass & Remote modes with Coarse & Fine manual tuning over the entire frequency range. Option 003 added a 5 digit frequency display.

Rear view
The rear panel has a BNC connector for remote operation and a special D-type connector for inter-connection to the HP 141T Display Section. For details see HP 141T External Connections.

Top view with the cover removed
Bottom view with the cover removed
2 special cables are required to connect the 8445B to the 141T & 8555A.

A rigid N-type coaxial cable is required to connect the 8445B output to the 8555A input (HP 08445-20022).

A special D-type cable is required to connect the 8445B automatic control input to the 141T Aux B output (HP 08445-60007).

April 2008

The 8445B arrived in very good condition and little work was required.

March 2009

Most of the performance tests completed.