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hewlett-pa: 350; Attenuators and Voltage Divider

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Forum » Radios and other type of sets (Physics) etc. » MODELS DISPLAYED » hewlett-pa: 350; Attenuators and Voltage Divider
Pius Steiner
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25.Sep.12 10:11

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"From HP Catalog 18A" Laboratory Instruments", Copyrighted 1945."

Large Power Handling Capacity
Wide Frequency Response
Smooth Operation
Convenient Controls

Attenuate the output of supersonic and audio oscillators
Measure gain and frequency response of amplifiers
Measure transmission loss
Increase usefulness of other laboratory instruments


For measurement work where accuracy, wide frequency response, large power handling capacity, or other special features are desired, -hp- attenuators and voltage dividers are extremely valuable. Typical of these highly specialized instruments is the -hp- Model 350 Attenuator Set.
The schematic diagram above shows the basic bridged-T circuit, two of which make up the -hp- 350 Attenuator Set. One is a 100 db attenuator, calibrated in 10 db steps, and one is a 10 db attenuator, calibrated in 1 db steps.
A special design assures a response that is substantially flat to frequencies as high as 100 kc. See figure 1. Calibration is accurate because the individual resistors are adjusted to ±1/2%.


The -hp-- Model 350 can be used wherever a decade attenuator is required. In conjunction with an -hp-- oscillator and one voltmeter, this -hp- Model 350 Attenuator may be used to make exact measurements of power gain. See figure 2. The 350 may also be used to augment an -hp- audio oscillator and a vacuum tube voltmeter (-hp-- 400A) to form a signal generator. See figure 3.

The 350 is built with a large power handling capacity-5 watts continuous duty. It is particularly adapted to-work in the supersonic field, and for other work in measurements above the range of the conventional a-f attenuator. It may also be used for work down to zero frequency.
The 350, like all -hp- instruments, is held to a minimum size for convenience in use. Actual dimensions are 5" x 8" x 41/2". Input and output binding posts are available on the front panel. The unit is completely shielded from moderate fields.

Figure 1


Attenuators, voltage dividers, matching networks, and precision resistors accurate for frequencies as high as one megacycle can be supplied. Inquiries pertaining to your particular measurement problem will be given prompt and careful attention.



Two models are available:
The -hp- 350A matches a 500 ohm impedance and
the -hp- 350B matches a 600 ohm impedance (one side grounded).

Attenuation: The attenuation is 110 db in 1 db steps.

Accuracy: Each individual resistor is adjusted to ±½%.

Frequency Response: Accumulative error at 100 kc approximately 1 db in 50 db.

Power Capacity: The attenuator will handle 5 watts continuous duty.

Mounting: The attenuator is mounted in a small wooden cabinet 5" x 8" x 4½".

Net Weight: 4 pounds. Shipping Weight: 8 pounds.


Precision multi-tap switches and other hardware for use in equipment for measuring work are also available. Two typical examples of this special-purpose hardware are shown below.


The -hp- flexible, coupler permits the accurate, positive transmission of motion from one shaft to another when the two shafts are not accurately aligned. Misalignments of as much as 1/32" and/or 5° are permissible. At the same time, the two shafts are insulated from each other, each shaft being connected to a different point on the ceramic body of the coupler. The coupler is spring-loaded to prevent backlash.



The -hp- No. 10 binding posts shown, were designed to provide a positive connection that could be changed frequently. The recess for the "Banana" plug is in the main body of the post, a feature which eliminates excessive contact resistance. The cross-hole for permanent connection can be used even when the "Banana" plug is inserted. The screw thread is 10-32 and the tip is undercut so that a soldered connection will not damage the thread. The long, axially-knurled ferrule provides a wide surface for ease of handling and adds to the appearance.

This article was edited 25.Sep.12 12:09 by Pius Steiner .