July Vol Viino

Low-impedance elements are a requirement of high-frequency measuring circuits. These arms are wound on thin mica cards. Both transformer and ratio arms are mounted on plug-in bases so that they may be transposed or new ones inserted. The balance condenser has a capacitance of 1000 ppi and is provided with a slow-motion friction drive. A small .vernier condenser of 15 p. pi allows the adjustment of the total capacitance to 0.01 fx pi. The variable resistance for...

Bridge Methods For Measurements At Radio Frequencies

Under measurement are at first used, and as experience and technique improve, more elaborate but more convenient and flexible methods are developed. The earliest methods of measuring resistance were the voltmeter-ammeter and later the substitution methods. Bridges, which increased the sensitivity of the substitution method by introducing a differential comparison and extended its range by using ratio arms, naturally developed from the substitution method. Bridges are now universally used for...

Wide Impedance Range

Made to deliver 50 milliwatts into that load. The introduction by General Radio of the output meter utilizing a rectifier-type voltmeter in conjunction with a constant-impedance multiplier made such power measurements considerably simpler. The output meter has had a wide acceptance in the field, in spite of The method of using the output power meter can be seen from an inspection of the engraved scales- Full-scale deflection of meter corresponds to 50 milliwatts for a multiplier setting of 1...

The Michelson Velocity Of Light Experiment

Nichols of the Department of Instrument Design at the Mount Wilson Observatory, Pasadena, for the accompanying description of the latest experiment to determine the velocity of light in a vacuum. Editor. HE following is a brief description of the Michelson velocity of light experiment in vacuum. This experiment, made at the Irvine ranch near Santa Ana, California, during the period from May, 1930, to July, 1931, by A. A. Michelson of the University of Chicago, F. G....

Measuring Pentodes With The Mutualconductance Meter

THE Type 443 Mutual-Conductance * Meter, developed several years ago for testing triodes, can he used equally well with four-element tubes. After a minor modification (which every unit in our stock now includes) both heater-type and filament type pentodes can be measured. One of the modified mutual-conductance meters with the batteries connected for measuring a filament-type pentode is shown in Figure 1 and the corresponding circuit in Figure 2. The connecting links to the new bind ing posts,...

Universal Bridge

HERE has been a marked increase in recent years in the use of bridge methods for the measurement of impedances of all kinds. This increase has come from the greater number of quantities to be measured, from the greater range of their numerical values, and from the greater range of frequency at which the measurements must be made. The values of the magnitude range and frequency range over which measurements are desired are impressive resistance from a microhm to a megamegolim, inductance from a...

Amateur Crystal Holder

The Type 560-A Crystal Holder assembled The crystal is held under light pressure The crystal is of course not included in the price of the holder In general, quartz-crystal holders for amateur and experimental-transmission use are constructed with two major considerations in view frequency stability and maximum power output. In amateur operation it is generally advisable to sacrifice some frequency stability to gain in power. The two types of holders commonly in use are the air-gap and...

Oscillograph

HE absence of any appreciable inertia in a beam of fast moving electrons gives the cathode-ray oscillograph an inherent advantage over all other types for the study of waveforms involving a wide range of frequencies. However, linear frequency response does not, in itself, guarantee a useful oscillograph, and it is only recently that tube limitations have been overcome and satisfactory auxiliary equipment developed to make possible exacting study of periodic phenomena up to 50,000 or 100,000...

The Wavemeter Yields

HE tuned-circuit wave-meter was the first accurate radio-frequency -mea -su ring instrument, and it is interesting that even now wre measure frequency with far higher accuracies than any other quantity with which the radio engineer deals. While tuned-circuit wavemeters have been greatly refined, the accuracy of laboratory measurements, and indeed commercial requirements for frequency standards, have outstripped them. So, wdiile the tuned-circuit type of wavemeter will still he used for many...

Miscellaneous Recent Developments

The instruments illustrated on pages 15 and 16 are all recent developments. All except the new Type 654-A Voltage Divider have been described in some of the previous issues of the Experimenter. The Type 654-A Voltage Divider is a combination of two sets of decade resistance units connected in series with the output voltage taken off across one set. When the resistance of the output unit is increased, the resistance of the other unit is simultaneously decreased to maintain constant total series...

Two New Potentiometers

Although the high resistance po-i tentiometers voltage dividers used in the control circuits of vacuum tubes and photo-electric cells are modified versions of the rheostats and potentiometers used in the early days of radio for the control of filament, grid, and plate voltages, present-day needs make many improvements desirable. Since many vacuum-tube circuits are calibrated it is, of course, important that resistors for use with them be fairly stable and be as free as possible from vagaries...

Testing Radio Receivers On The Assembly Line

Standard-Signal Generator lias proved to be a most useful instrument for these tests. Figure 1 on the next page shows them in the final production line at the Roister Radio Corporation's factory in Newark, New Jersey. In order to take care of the peak production from this plant, ten test positions are necessary. Each one has its Type 601-A Standard-Signal Generator mounted upon a cabinet containing two loud-speakers one is a stand-by in case of trouble and an output meter. The completely...

Inexpensive Noisemeasuring Equipment

ORE and more industry is realizing the fatiguing effects upon human beings of the various noises to which they are subjected, and with the realization comes the endeavor to reduce, so far as practical, all unnecessary sounds. In New York City for example, a noise commission has been making an exhaustive survey of the sources of city noise and means of its prevention. The most disturbing noises are frequently those generated by some common piece of mechanical equipment during its normal...

Variable Inductors For Bridge Measurements

IT is a peculiarity of bridge measure- raents practice that, while variable continuously adjustable capacitance standards are almost universally used in preference to fixed standards, a general preference for fixed inductance standards over variable standards has prevailed. There are, as a matter of fact, many cases where measurement methods can be improved by the use of a continuously adjustable inductor or variometer. The use of such an instrument permits the use of equal arm bridges for...