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HP 8555A RF SECTION
The HP 8555A RF Section is used with the HP 141T Display Section and the HP 8552B IF Section to make a Spectrum Analyser. It cost $7,700 in 1980. I have the paper and various downloaded Manuals and Change Notes.

The 8555A will operate over a bandwidth of 10MHz to 18GHz. With an external mixer the 8555A will operate up to 40GHz, see HP 11517A External Mixer for details.

Front view
If not in use, the External Mixer, First LO Output and Second LO Output should all be terminated in BNC 50Ω Terminations (HP 11593A). The RF Input on the N-type connector is susceptible to burnout if fed an excessively high signal or dc level.

Rear view showing P2, P4 & P5 connectors
Rear Panel connections to the 141T. For details of P2 see HP 141T Internal Connections. P4 connects to the HP 8444A Tracking Generator and P5 connects to the HP 8445B Automatic Preselector, for details see HP 141T External Connections.

Top view with the screen cover removed
Bottom view with the screen cover removed
This is the Mixer which can be damaged by overloading the input. +10dBm 10mW maximum. Apparently it can be repaired but an expensive mistake to damage it in the first place!

Use maximum attenuation when applying input signals of unknown amplitude. The attenuator is in between the input N-type connector and the Mixer. +33dBm 2W maximum. Also maximum voltage is ±20V dc, 0.707V rms, 1.0V peak. With dc on the signal don't change the input attenuation switch.

August 2008

Apart from a good clean, this worked ok on first power-up. In normal use, the 8555A will operate up to 18GHz which is more than high enough for me. Satellite channels operate in the 10 to 12GHz band. So the 11517A Extenal Mixer is not required.

Testing of this RF Section revealed a few minor issues. Setting up the log & linear vertical position and gain was a bit tricky due to an intermittant connection. The 2nd LO at 1,500MHz and 3rd LO at 500MHz are not exactly within specification.

Some of the final performance tests were not done as these needed a Comb Generator. Apart from these issues, which I will resolve later, the RF Section is OK.


November 2014

No vertical display on the Spectrum Analyser. Substituting this 8555A for a 8553B and all ok. See Repair HP 8555A RF Section for details. Now working again.