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WTCN-FM, Minneapolis, goes on the air with most efficient FM Antenna installed anywhere ..... boosts 3kw transmitter to 25kw .... with coverage of 30,000 square miles.
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Federal's 8-Element Square-Loop Antenna made radio history with the opening of the "Twin Cities" FM station, WTCN - the first super-directive antenna of its type and power gain to be installed anywhere.

It gives the 3kw Federal transmitter an effective radiated power of 25kw - providing excellent reception over an area of approximately 30,000 square miles.

This makes WTCN the world's most efficient FM station - and, with an FCC permit for an output of 400kw, it will eventually be one of the country's most powerful stations, too.

With 'Federal's high-gain antenna, this maximum rating of 400kw can be achieved with the installation of only a 50kw transmitter !

WTCN is among the FM stations with permits for the most powerful ratings in the country. Others are KWK, St. Louis, with 369kw - and WTMJ, Milwaukee, with 349kw. These three stations have all selected FM by Federal! And Federal can equip your new FM station, too - from microphone to antenna.

Station: WTCN was officially opened by a gala inaugural program featuring the Minneapolis Symphony Orchestra, Dimitri Mitropoulos conducting. With FM by Federal, listeners at home were enabled to hear this famous orchestra with the same brilliance and tonal color as the studio audience. Insert shows Mr. Mitropoulos and Governor Luther W. Youngdahl of Minnesota, at opening of ceremonies.

"Wonderful! Magnificent! A terrific step of progress." This was the comment of the famed conductor, Dimitri Mitropoulos, when he heard his own orchestra over an FM receiver, during an on-the-air rehearsal.

Write today for complete information. Dept.. B343. Newark 1, New Jersey.
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The world's first permanent super-efficient FM antenna erected by Radio Station WTCN-FM atop the Foshay Tower. Minneapolis, Minn. The eight-element square-loop antenna and FM broadcast transmitter installed by WTCN-FM were manufactured by Federal Telephone and Radio Corporation, associate of the International Telephone and Telegraph Corporation. Radiated power is 400 kw.

According to Federal Telephone and Radio Corporation engineers the 8-element square-loop antenna multiplies the power of the transmitter by over eight times. As a consequence, with a 3kw transmitter now in operation an effective radiation of better than 25kw is recorded. When the power of the transmitter is increased to 50kw, the antenna will provide an effective radiated power of 400kw with resulting advantages to WTCN-FM audiences.

An instrument which may make possible further improvements in the recording of music on magnetized wire was reported recently before the winter meeting of the American Institute of Electrical Engineers (IEE).

The instrument, called a "cathode-ray oscilloscope hysteresis loop tracer," was announced in a paper by D. E. Wiegand and W. W. Hansen, both of the Armour Research Foundation of the Illinois Institute of Technology, Chicago, prepared for presentation before the Convention's Communications Section. Both men have been prominent in research on wire recording.

Designed as a research tool, the instrument continuously pictures on a lighted screen the magnetic properties of the recording wire being tested, thus making possible rapid and detailed analysis of new combinations of alloys. It can test samples much smaller than can be used conveniently with the present ballistic test method, the authors stated, and magnetic readings with a consistent accuracy within five per cent are possible.

Engineers are searching for new types of recording wire because an improved wire means greater fidelity in the recorded program or, where cost is a prime consideration, will allow the present high fidelity characteristics to be maintained with a reduction in wire speed.

The new instrument can also be 11366* to test the magnetic properties of alloys at each stage of their manufacture into wire, thus ensuring uniform wire quality. Some variations exist in the magnetic quality of recording wire now being produced.

These variations do not cause noticeable distortion of tone or volume, but engineers are striving to make magnetic recording more nearly perfect in this respect also.

"The alloys presently used in the manufacture of recording wire depend on cold working for their magnetic properties and by measuring these properties at various stages in the drawing process, it is possible to predict the properties of the wire when drawn to the final size," the authors stated.

"Magnetic measurements on a particular alloy at various diameters in the drawing process, moreover, make possible determining the annealing and drawing schedule required to produce a wire of given magnetic properties."

The instrument consists of a 35-pound exciting coil with pickup coil at its center, an amplifier and integrating circuit, and a cathode ray oscillograph. It operates at power line frequency, making practically unlimited power available without the use of oscillators or motor generator sets, and is described by the authors as "rugged and simple in operation."

The "Institute of Radio Engineers" held its annual "latest-in-electronic developments" Convention, March 3-6 (1947) inclusive. It proved to be one of the most consequential meetings in the historv of the I.R.E.
Over 150 manufacturers exhibited the most recent fruits of radio and electronic research at New York's Grand Central Palace over the four-day period.
For non-members as well as members of the Institute, there was the reading of 124 highly technical papers of vital consequence to the most recent developments in radio and electronic engineering (see program for times and locations).

A new portable three-inch oscilloscope meeting laboratory requirements for accuracy is now in production, it was announced by W.W. Watts, Vice-President in Charge of the RCA Engineering Products Department. The new oscilloscope's frequency range and high-gain characteristics permit close examination of highspeed transients and pulsed voltages for test analysis. This oscilloscope, Type WO-79A, makes possible the accurate measurement and display of frequency components up to 6mc (6 MHz)in transient and pulsed voltages of the order of one microsecond.

The centering controls on the oscilloscope permit expansion of a waveform under test over a distance which is twice the diameter of the screen, without causing visible distortion. This makes it possible to center any portion of a complex wave on the screen for analysis. The voltage amplitude of a signal can be determined by means of a calibrated voltmeter which is built into the front panel of the instrument.

The triggered sweep feature makes the unit particularly suitable for photographic study of transient waveforms, for television signal expansion for checking square-wave time, and for checking irregularly timed pulses. The intensifying amplifier increases the brilliancy of the waveform after the time-base generator is triggered, permitting examination and photography of small, otherwise, faint, and extremely short pulses.

Signal-triggered deflection, line frequency deflection, and blanking are some of the other unusual features of this new RCA oscilloscope.

Some of the applications of the new oscilloscope include square wave testing for frequency response characteristics: adjustment of radio, television, telegraph and telephone channels, and r-f and i-f amplifiers ; observation of common types of waveforms; measuring speed and time intervals ; measuring impedance and power factor in loudspeakers and other devices: timing fine watches; and measuring percentage of modulation.

A new 156-page receiving tube brochure, Recommended Types (ETR-19), for equipment designers and radio set manufacturers, has been published by the Tube Division of General Electric Company's Electronics Department.
Covering the complete G-E and Ken-Rad receiving tube line and its associated circuit, the new publication lists tube types in numerical order by sections. Each section includes a typical circuit, complete ratings, curves, and companion technical data for each tube type.
Practically any receiver circuit is outlined in the new publication. Distribution of the Recommended Types Brochure will be made to receiver manufacturers, designers, and engineers.
Equipment manufacturers and radio set designers may obtain a copy of the new publication by writing W. Hayes Clarke, G-E Electronics Department's Tube Division, Schenectady, N. Y.

A new Unimeter, Type YMW-1A, designed for simplicity of of eration and high accuracy, has been announced by the Specialty Division of General Electric Company's Electronics Department.
Designed for rapid, accurate measurement of volts, ohms, current and decibels, the YMW-1A is especially adapted for service work but also may be used in general laboratory and industrial applications. It is a 20.000 ohms per volt multi-range instrument.
All functions of this nine-pound equipment except the 50 microamps and output meter capacitor jacks, are available without changing the test leads. A single rotary selector switch controls all the operations and ranges.
The YMW-1A specifications include resistance with a total coverage of 1 ohm to 20 megohms; voltage, a-c and d-c, 0-1000 volts; current, 0 to one-half ampere ; decibels, minus 4 to plus 62, all designed in convenient ranges.
Further information on the new Unimeter may be obtained on request to the Wolf Street Plant, G-E Electronics Department's Specialty Division, Syracuse, N. Y.
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1. Allied Radio Corp.
2. Calumet Iron & Supply Co.
3. Concord Radio Corp.
4. Federal Tel. & Radio Corp.
5. Hopp Press, The
6. Measurements Corp.
7. Mid-America Co., Inc.
8. Racon Eleclric Co., Inc.
9. Radio Paris and Electronic Equipment Shows, Inc.
10. Rider, John F. Publisher, Inc.
11. Simpson Electric Co. Coverpage
12. Sylvania Electric Products Inc. Coverpage
13. Tech Laboratories
14. U. S. Treasury Dep't.
15. Wrigley, Win. Jr. Co.

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• Anmerkung : Diese sehr "aufgeräumte" Liste zeigt, sehr ähnlich zu den deutschen Hifi-Magazinen kurz vor Toresschluß, daß sie mit ihren Anzeigen die Ausgaben nicht mehr decken konnten. Die Neuorientierung zur Hifi-Szene war also zwangsläufig.

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