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The HP 8412B Phase - Magnitude Display is for use with a HP 8407A Network Analyser or a HP 8410C Network Analyser for displaying the relative phase and magnitude in cartesian form. The original cost was $2,750 in 1980. A HP Manual was downloaded from the Web.

Front view
Rear view
This plug-in unit contains a CRT which displays test signal amplitude and phase on 2 separate traces. Amplitude is displayed in dB/division and phase in degrees/division.

External Connections

Front Panel

Rear Panel
SWP IN [BNC] from Generator/Sweeper to provide x-axis sweep
AMPTD 50mV/dB [BNC] *
PHASE 10mV/Deg [BNC] *
Z-AXIS [BNC] intensifies trace with -5V, blanks trace with +5V
PHASE CONTROL [BNC] connecting to ground causes a 180° offset, only used with automatic network analyser system
NORMALISER INTERCONNECT [Special D-type 5 coax & 17 sockets] to HP 8750A Storage Normaliser

* The rear panel outputs for PHASE and AMPLITUDE are useful for monitoring on an oscilloscope or DMM to provide an indication of the amplitude and phase difference between the signals.

Amphenol Blue 24 way Connector for 8407A, 8410C, 8418A Mainframes and 8412B, 8414A, 8414A Plug-Ins, see Network Analyser Internal Connections for details.

April 2007

Bought the 8412B (S/N 2417A) on eBay DE.

November 2007

Bought a 2nd unit (S/N 2246A) on eBay UK together with a 8407A.

January 2011

Started testing (S/N 2417) with the 8407A, see HP 8407A Network Analyser for details. The Operating and Service Manual for the 8412BA explains how to make: single frequency transmission measurements; single frequency reflection measurements; swept frequency transmission measurements; and swept frequency reflection measurements.

Screen and Graticule
The screen and graticule is a bit difficult to read as there is no internal illumination. It measures 10cm horizontally by 8cm vertically. After various adjustments and performance tests, this unit is ok. Started testing the 2nd unit (S/N 2246A) and this is not working correctly, see Repair HP 8412B Phase - Magnitude Display for details. This unit will be kept as a maintenance spare.

Next task is to work through HP Application Note 121-1 "Network Analysis With The HP 8407A 0.1 - 110MHz" to gain a better understanding of the 8412B. See Operating HP 8407A Network Analyser for more information.