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Azur Electronics

I bought this for only £20 as it had the probe tip missing. The original cost was $1,750 in 1980. The 3406A is a very useful and unique item of test equipment as it can measure voltages in high impedance circuits at high frequencies up to 2GHz. A Manual was downloaded.

The 3406A uses a unique "incoherent" sampling technique to translate a high frequency input signal into a low frequency equivalent (a good explanation is provided in the Manual).

This gives it a wide badwidth of 10kHz to 1.2GHz, with useful sensitivity from 1kHz to >2GHz. Full scale sensitivity from 1mV to 3V is selected in 8 steps of 10dB and may be read directly from -62dBm to +23dBm.

The push-button on the probe retains the measurement until released. Various accessory probe tips are available to facilitate different measurements in high impedance and 50Ω circuits.

2 BNC Outputs on the Rear Panel are Sample Hold and Recorder.

The Sample Hold output provides a statistically equivalent signal to the input which gives true rms, peak voltage, amplitude modulation envelopes and pulse height information.

The Recorder output provides a d.c. level proportional to meter deflection.
May 2009

Apart from the missing probe tip, the 3406A was in very good condition and only needed a few labels removing and a good clean up.

2 new probe tips were acquired (with thanks to Steve K) and the 3406A powered up ok and seems to function correctly.

The HP 11064A Accessory Probe Kit includes a number of items of which I have only 3: the 11072A Isolator; the 5060-4991 Ground Lead; and a spare Probe Tip 5020-0457. Other accessories which would be useful are the: 11063A 50Ω Tee; 11061A 10:1 Divider; 10218A Probe to BNC Adaptor.

Performance Testing has been completed, although by substituting more modern test equipment than specified. My requirement is for the 3406A to provide an indication of signal levels at high frequencies and in high impedance circuits, rather than a calibrated measurement.

January 2016

As I only use the 3406A occasionally, some operating notes will save time.

To Calibrate, insert the probe with the Isolator Tip into the receptacle with the CAL switch out. Adjust the ZERO control for '0' on the meter scale. Press the CAL switch in to provide a 1Vrms signal. Adjust the CALIBRATE control with a small slotted screwdriver for 1Vrms on meter scale. Repeat if probe tip is changed.

 Switch   In/Out   Level 
Power Off/On
Range  .001Vrms   -50dBm 
Range .003Vrms -40dBm
Range .01Vrms -30dBm
Range .03Vrms -20dBm
Range .1Vrms -10dBm
Range .3Vrms 0dBm
Range 1Vrms +10dBm
Range 3Vrms +20dBm
 Calibrate  On/Off