Amplifiers

HOWEVER much engineering development the manufacturer of an audio-frequency amplifier expends on its design, there remains the problem of comparing the performance of the quantity-produced unit with that of the laboratory model. Without rigorous inspection some defective units are likely to reach the user, which makes necessary expensive replacements and breeds ruinous ill will. Some manufacturers check the component parts before assembly and follow this with a supplementary...

Service Laboratory

Trade Show in Chicago early this month and in its advertising, the General Radio Company announced that several new items of test equipment for the radio service man were being developed. So many requests for information have been received that the following descriptions are being published, even though all three instruments are still in our laboratory undergoing their final tests. These specifications must, therefore, be regarded as preliminary and subject to...

Units of Electrical Transmission

The communication engineer, although he deals generally with very small amounts of energy, is frequently concerned with ratios of energy having enormous magnitudes. The ratios between the rates of energy flow in different parts of a communication system, if expressed numerically, may be quite as impressive as the figures used by the power engineer. As an example the power delivered by an ordinary telephone transmitter is of the order of 0.01 watt. This may be used to control the output of a...

A Rectifier Type Meter for Power output Measurements at audio frequencies

IN the course of routine experimental work in the laboratory there often occurs the need for a convenient means of measuring the power delivered by a device at frequencies for which the ordinary dynamometer-type of wattmeter fails. This problem might, for instance, appear when testing the audio-frequency amplifiers of a public-address system or when making the standard fidelity, sensitivity, and selectivity tests upon radio receivers. In each instance the power output of the tested device is...

Frequency Determination

ONE need be only a casual reader of current radio literature to know that the precision determination of frequency is a most important engineering problem. The growing economic, political, and social significance of all radio channels is requiring an increasingly precise distribution of services over the useful frequencies of the spectrum. Already the Federal liadio Commission requires that the broadcasting station's carrier frequency at the high-fre-quency end of the band be maintained within...

C o m m unica t ion circui t s

Determining the transmission characteristics of communications apparatus is, like all other problems in measurement, nothing more than the judicious application of certain standardized definitions. A possible difference may be claimed in the fact that these quantities are defined, for convenience, as the logarithm of a ratio where almost every one else would be content to talk about the simple arithmetical ratio. But to claim special privilege on that score would be a most puerile form of...

Notes on power Measurement in communication Circuits

ANOTHER communication meas-j urement problem makes its appearance when it is desired to determine experimentally how much power a given power source is capable of delivering to a specified load or sink. So long as the source itself is available for test, it is merely necessary to set up the equipment and make the measurements. If, however, the source is not available, some means must be found of simulating it. At least two methods for doing the job are available, and we propose to describe...

How and Why the Talkies

LAMSON, Engineering Department In the December issue of the EX-I'EHIMENTER we outlined the general problems of the talking movies and discussed in some detail the wax disc method of recording and reproducing synchronized sound. We now propose to consider the optical method whereby a photographic record, corresponding to the fluctuating sound impulses, is obtained upon a film in the studio and subsequently reproduced as sound in the theater. There are two fundamental forms which...

Miscellany

WI TH this number, the first of Volume IV, the General Radio Experimenter appears in a new format. The new page is only one-half as large as the old one 6 inches by 9 inches instead of 9 inches by 12 inches , but doubling the number of pages makes it possible to include as much Besides making it easier to handle, the smaller size brings the Experimenter more nearly into uniformity with other publications which the reader keeps for reference. No other radical changes either in the editorial or...

Experimenter

The General Radio EXPERIMENTER is published each month for the purpose of supplying information of particular interest pertaining to radio apparatus design and application not commonly found in the popular style of radio magazine. liiere is no subscription fee connected with the General Radio EXPERIMENTER. To have your name included in our mailing list to receive future copies, simply address a request to the THE TWO-STAGE MULTIVIBRATOR AND TIMING AMPLIFIER FOR THE NEW FREQUENCY. DETF.R MI....

New Frequency Standard

THE TWO-STAGE MULTIVIBRATOR AND TIMING AMPLIFIER FOR THE NEW FREQUENCY. DETF.R MI. NATION EQUIPMENT I FREQUENCY, like other physical quantities, is i measured by comparing the unknown with a standard whose value has been established either absolutely or arbitrarily by general agreement. We measure length with a yardstick, which has been compared by means of many intermediate measurements with the length of a certain bar recognized as the international standard. Similarly, we may measure...

Improving the Precision of setting in a Tuned Circuit Wave m ete r

THE difficulty in observing accurately the true resonance setting of the variable condenser in a tuned-circuit wavemeter is known to any one who has attempted to make precision measurements by looking for the current maximum. The peak of the resonance curve is so flat that the precision of setting the condenser is often far less than the inherent accuracy of a high-grade tuned-circuit wavemeter. These difficulties have led to the development of the incremental capacity method for indicating...

Y Low Frequency Oscillator

RECENTLY the increased attention paid to the operation of - broadcast circuits at the lowest audible frequencies has created a demand for measuring equipment to cover this range. With this in view the General Radio Company has extended the frequency range of its Type 377 Low-Frequency Oscillator to include all frequencies lying between 25 cycles and 70,000 cycles. At the same time that this change was contemplated it was thought desirable to design the new oscillator for use with one particular...

PiezoElectric oscillators

Piezoelectric Oscillators

OUARTZ plates for use as standards of frequency in piezoelectric oscillators must be kept under temperature control if constancy of frequency is to be expected. It is impossible to make a general statement about the frequency of such an oscillator as a function of the temperature of the plate, because the frequency-temperature coefficient varies considerably with the way the plate is cut. Even among plates of the same cut taken from the same mother crystal, the coefficients are not alike. It...