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This is a Tracking, Signal, or Sweep Generator for use with the Spectrum Analyser 8554B (500kHz to 1,250MHz) and 8555A (10MHz to 1.3GHz) RF Sections.  The Generator converts the 1st and 3rd Local Oscillator outputs from the RF Sections and mixes them with a 1.55GHz Oscillator to provide an output that tracks the tuning frequency of the Spectrum Analyser.
This cost $3,500 in 1977.  I have both the paper and downloaded Manuals.
Front view
The front panel has:
1) RF Output N-type, for connection to the equipment under test, or direct to the Spectrum Analyser for calibration.
2) 3rd Local Oscillator Input BNC, 500MHz for connection to the 8554B.
3) 1st Local Oscillator Input BNC, for connection to the 8554B (2.05GHz to 3.3GHz) or the 8555A (2.05GHz to 4.1GHz).
4) Scan Output BNC, manual tune voltage 0V to +10V to 8552B.
Rear view
The rear panel has:
1) Aux RF Output BNC, same frequency as the front panel RF output, for use with a frequency counter when in manual scan mode.
2) 3rd Local Oscillator Input BNC, paralleled with front panel BNC, 500MHz for connection to 8555A via the special cable and rear D-type connector on the 141T.
Top and bottom views with the covers removed.
The connections required to the Spectrum Analyser are:
For the 8444A to 8554B, 3 BNC coaxial cables are required (HP Part No 08444-60018): 1st L.O. Input to 1st L.O. Output; 3rd L.O. Input to 3rd L.O. Output; Scan Output to 8552B Scan In/Out.
For the 8444A to 8555A, 2 BNC coaxial cables are required: 1st L.O. Input to 1st L.O. Output; Scan Output to 8552B Scan In/Out.  A special cable (HP Part No 08444-60017 available from GLK Instruments) is also required: 3rd L.O. Input BNC on rear panel to Aux A Output D-type on 141T rear panel.  This is because the 8555A does not have a 3rd L.O. Output on its front panel.  For details see HP 141T External Connections.
This applies to serial numbers above 1147A.
2 Options were also later available:
Option 058 is for use with the HP 180 and HP 8558B Spectrum Analyser.  It adds a 500MHz 3rd Local Oscillator circuit to the Tracking Generator as this is not available from the 8558B.  The frequency range is unchanged at 500kHz to 1.3GHz.  An extra BNC connector is available on the rear panel for the 3rd L.O. Output.  This is connected via a short BNC cable to the rear panel 3rd L.O. Input.
Option 059 includes 058 and extends the frequency range to 1.5GHz with >90dB dynamic range.  The output is calibrated at 0dBm and variable to -10dBm.  This cost
$4,425 in 1980.
August 2008
Some work was required to the 8444A, apart from the usual label removing and good clean up.  The left hand side handle was bent in transit.  This required the side extrusion removing, the handle straightened and the crack re-welding.  The power switch had been replaced at some time, this required rewiring and insulating the live connections.  The output 'level' control had no effect, which is apparently a common problem.  This required carrying out all the adjustment procedures which include calibrating the 0dBm and -10dBm output level limits.  Luckily this was not a fault condition as the amplifier is a LSI circuit (shown in the bottom view) which is probably not repairable, or easily replaceable any more.  The 8444A now works ok with the Spectrum Analyser.  Progress!