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Azur Electronics

The HP 8407A Network Analyser mainframe operates from 100kHz to 110MHz. With a plug-in Display Unit (8412B, 8413A or 8414A) and a carrier wave or swept frequency source (8601A), this 2 input tracking receiver measures the amplitude and phase ratio of RF signals. The original cost was $5,350 in 1980.

A HP Manual was downloaded from the Web. Very useful reference sources are HP Application Notes 121-1 "Network Analysis With The HP 8407A 0.1 - 110 MHz" and 121-2 "Swept Impedance With The 8407A Network Analyzer 0.1 - 110 MHz".

Front Panel Controls and space for Plug-In units
Rear Panel Connections
External Connections

Front Panel
REF CHANNEL ATTEN (40dB) [BNC] +20dBm to -50dBm
TEST CHANNEL ATTEN (40dB) [BNC] +20dBm to -50dBm
NOTE: Damage level is +26dBm 50Vdc

Rear Panel
POWER [CEE22 Plug]
VTO in [BNC] RF + 200MHz from Generator/ Sweeper to phase-lock system
IF REF [BNC] 278kHz at 1.4Vpp 50Ω *
IF TEST [BNC] 278kHz at 320mVpp 50Ω *

* IF REF & IF TEST are at the same point in the circuit as the inputs to the plug-ins, so these outputs are a useful monitoring point for an oscilloscope to show 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.

November 2007

Bought the 8407A (S/N 1317A) on eBay UK together with a 8412B.

December 2007

The Network Analyser was completely stripped down, cleaned up, a few minor faults repaired and re-assembled.

The Display Reference indicator is unusual as it uses a printed film strip which has become tarnished over the years and is somewhat fragile. This makes it a bit difficult to read but I decided not to attempt cleaning in case it wiped the data.

Testing is held up as it needs a HP 8601A Generator/Sweeper which provides the RF and VTO signals required.

Film Strip Indicator
January 2011

After 3 years delay, the HP 8601A Generator Sweeper has been acquired, repaired and tested. Started testing the 8407A using the 'Transmission Test Setup" and the HP 8413A Phase -  Gain Indicator which is the most basic of the 3 Plug-In's. Alignment Procedures carried out and some adjustments required to get the Generator and Network Analyser in phase-lock.
Testing 8407A & 8413A
Started testing the 8407A using the 'Transmission Test Setup" and the HP 8412B Phase - Magnitude Display.

WARNING: with the covers removed on the 8412B, 3kV high voltage is exposed.

Alignment Procedures carried out and some adjustments required to get the Display operating correctly.

Testing 8407A & 8412B
Completed the 8407A Troubleshooting Tree, Adjustments and Performance Tests. Mostly ok but a few minor issues with the phase-locked loop and adjustments 6 & 7 which will need some more work when I have time, or if they cause any problems.

NOTE: It is essential to ensure that the 8407A is phase-locked to the 8601A. The REF CHAN LEVEL Meter needs to be in the OPERATE zone. Also, it is a good idea to monitor the IF REF & TEST outputs on an Oscilloscope to ensure the 278kHz signals are phase-locked.

February 2011

Tested the 8407A with the HP 8414A Polar Display. One is tested ok, the other is faulty and will be kept as a maintenance spare.

This Network Analyser with the 3 Plug-In Displays is a fairly complex system to operate, see Operating HP 8407A Network Analyser for more information.

Testing 8407A & 8414A
Using the HP 8407A with the HP 8418A Auxiliary Display Holder provides the opportunity to have 2 Display Units working at the same time. To achieve this, the 8407A needs to be modified. This was Option H03 and provided 4 additional BNC outputs: REF; TEST AMPL; TEST PHASE; & BLANK to drive the 8418A.

Option HO3 Modification
These outputs are wired in parallel to the same outputs to the Display Units. See Network Analyser Interconnections for details.

8407A with 8412B and 8418A with 8414A
8407A Network Analyser System
March 2019

After repairing a tricky fault in the 8407A, in a feedback loop affecting several sub-assemblies, re-checked the entire system.

I now have all the equipment on top of a mobile cupboard which makes it easy to wheel up to my bench when required. Plus access to the rear cabling and connectors are facilitated.

August 2019

All the 8407A & 8410C based Network Analyser System has now been Sold.