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Sep 1940

Volume 11, Issue 9, pp. 273-300

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An Ultra‐High Frequency Superheterodyne Receiver for Direction Finding

Luke C. L. Yuan and Charles E. Miller

Rev. Sci. Instrum. 11, 273 (1940); http://dx.doi.org/10.1063/1.1751708 (4 pages)

Online Publication Date: 27 December 2004

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An ultra‐high frequency superheterodyne receiver, simple in operation, having high sensitivity and stability, was constructed primarily for direction finding on 1.67‐meter waves. The 220‐kilocycle intermediate frequency amplifier using resistance coupled high μ television type tubes has a constant gain of 110,000 over a 110‐kilocycle band. This flat intermediate frequency response allows for any slight variation in the oscillator or signal frequency, due to temperature variations etc., without affecting the output of the receiver. A high gain and a high signal to noise ratio make the receiver well suited for direction finding observations by the null point method.

Baffles for Oil Diffusion Pumps

Richard S. Morse

Rev. Sci. Instrum. 11, 277 (1940); http://dx.doi.org/10.1063/1.1751709 (5 pages) | Cited 5 times

Online Publication Date: 27 December 2004

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Although in the use of oil diffusion pumps for the production of high vacuum, extremely cold traps in the usual sense are not required, some means must be provided to prevent both direct backstreaming and diffusion of the oil vapor. The relative advantages of (1) charcoal traps, (2) cold traps, (3) hot baffles, (4) electrical baffles, (5) mechanical baffles are discussed and specific designs for effective high speed baffles are given.

On the Construction of Very Sensitive Vacuum Thermoelectric Cells

F. T. Rogers

Rev. Sci. Instrum. 11, 281 (1940); http://dx.doi.org/10.1063/1.1751710 (2 pages)

Online Publication Date: 27 December 2004

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A new and reliable technique is described for the construction of thermocouples of high sensitivity, suited especially to astrophysical research. The technique consists essentially of a controlled‐heating soldering process for very small bismuth alloy parts. The mounting of such thermocouples in permanently evacuable glass envelopes is also discussed.

An Electrical Integrator for ``Action Currents''

G. L. Freeman and E. L. Hoffman

Rev. Sci. Instrum. 11, 283 (1940); http://dx.doi.org/10.1063/1.1751711 (2 pages) | Cited 5 times

Online Publication Date: 27 December 2004

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An apparatus is described for integrating bioelectric potentials over various time intervals. This is accomplished by recording the number of times a gas‐filled tube discharges a condenser which stores the rectified potentials.

A Comparative Study of Water Aspirators

E. P. Little and S. E. Pond

Rev. Sci. Instrum. 11, 285 (1940); http://dx.doi.org/10.1063/1.1751712 (2 pages)

Online Publication Date: 27 December 2004

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The relative speed of evacuation, water consumption, air pumping ability, and final vacuum produced by 14 water aspirators have been measured, making possible a more intelligent choice of aspirator for any job.

A Multi‐Channel Delay Unit

Wade H. Marshall and Samuel A. Talbot

Rev. Sci. Instrum. 11, 287 (1940); http://dx.doi.org/10.1063/1.1751713 (3 pages) | Cited 5 times

Online Publication Date: 27 December 2004

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Details are given for the construction of a time delay circuit of particular value for physiological laboratories using oscillographs for studying action potentials of the nervous system. It permits timing separate events at any interval in a cycle of operation determined by a master oscillator. The operation of the circuit depends on the grid extinction of a thyratron operating at low current.

A Multiple Sweep System for Cathode‐Ray Oscillography

Samuel A. Talbot

Rev. Sci. Instrum. 11, 289 (1940); http://dx.doi.org/10.1063/1.1751714 (3 pages) | Cited 3 times

Online Publication Date: 27 December 2004

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The usefulness, efficiency and economy of cathode‐ray oscillography are improved by sweeping the spot across several successive lines on the face of the tube. There is presented a circuit which does this, with flexibility as to speed, delay, spacing and brightness of the individual traces. A modified sweep circuit actuates a trigger unit which shifts each trace and brightens it during the transit.

Design and Performance of an Electron Diffraction Camera

J. E. Ruedy

Rev. Sci. Instrum. 11, 292 (1940); http://dx.doi.org/10.1063/1.1751715 (4 pages) | Cited 2 times

Online Publication Date: 27 December 2004

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An electron diffraction camera has been built for use in the study of photo‐ and secondary electron emissive surfaces. The electron beam is produced by a modified cathode‐ray tube gun having an a.c. heated tungsten wire cathode, for which the focusing voltages are supplied by rectifiers. Beam velocities up to 40 kv are available. The maximum beam current, after reduction by a screening aperture, is about 0.1 μa, which is sufficient to make visible most patterns which can be photographed. The specimen adjustment mechanism and photographic shutter control are of new design and have proved themselves very satisfactory. The pumping system consists of a Megavac fore pump and a four‐inch diameter three‐stage oil diffusion pump.

Crystal‐Structure Models for Close‐Packed Systems

D. B. Langmuir and R. B. Nelson

Rev. Sci. Instrum. 11, 295 (1940); http://dx.doi.org/10.1063/1.1751716 (3 pages) | Cited 2 times

Online Publication Date: 27 December 2004

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Modified Cenco Impulse Counter

A. A. Petrauskas and D. L. Northrup

Rev. Sci. Instrum. 11, 298 (1940); http://dx.doi.org/10.1063/1.1751717 (1 page)

Online Publication Date: 27 December 2004

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A Low Frequency Alternator

Wesley M. Roberds

Rev. Sci. Instrum. 11, 299 (1940); http://dx.doi.org/10.1063/1.1751718 (1 page)

Online Publication Date: 27 December 2004

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Calcium Metaphosphate as a Target for Bombardment of Phosphorus by High Voltage Ion Beams

D. E. Hull and J. H. Williams

Rev. Sci. Instrum. 11, 299 (1940); http://dx.doi.org/10.1063/1.1751719 (1 page)

Online Publication Date: 27 December 2004

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High Current Capillary Mercury Arc Sources for Large Monochromators

Fred M. Uber

Rev. Sci. Instrum. 11, 300 (1940); http://dx.doi.org/10.1063/1.1751720 (1 page)

Online Publication Date: 27 December 2004

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