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News Briefs
July 1967 Radio-Electronics

July 1967 Radio-Electronics

July 1967 Radio-Electronics Cover - RF Cafe[Table of Contents]

Wax nostalgic about and learn from the history of early electronics. See articles from Radio-Electronics, published 1930-1988. All copyrights hereby acknowledged.

With as much ink as was used in reporting on this "Major Antenna Breakthrough?" item in the July 1967 issue of Radio-Electronics magazine, it could have qualified as a feature story. The breakthrough is an active antenna, dubbed a Subminiature Integrated Antenna (SIA), with amplifying transistors in series with the radial elements. This hookup makes practical, it is claimed, to reduce antenna length from 1/4 to 1/50 wavelength and still have reasonable signal pickup. A TV or FM receiver version could be 2 or 3 inches long. Half a year later the magazine had an SIA article entitled "Build a Mini-Tenna," which operated in the 88-108 MHz FM radio band. There does not seem to have been a widespread adoption of active antennas for most applications; however, they are found today significantly in GPS units and the satellite radio antennas on top of your vehicle. At this point, they are useful mostly for receivers due to power handling limitations. 

News Briefs: 11/57 | 8/58 | 11/59 | 2/60 | 4/60 | 8/60 | 9/60 | 10/60 | 12/60 | 1/61 | 3/61 | 5/61 | 6/61 | 7/61 | 8/61 | 9/61 | 10/61 | 11/61 | 12/61 | 1/62 | 2/62 | 3/62 | 4/62 | 5/62 | 7/62 | 8/62 | 9/62 | 10/62 | 11/62 | 3/63 | 4/63 | 6/63 | 8/63 | 9/63 | 11/63 | 2/64 | 3/64 | 7/64 | 8/64 | 12/64 | 8/64 | 9/64 | 1/66 | 3/66 | 8/66 | 9/66 | 1/67 | 3/67 | 4/67 | 5/67 | 6/67 | 7/67 | 9/67 | 3/68 | 4/68 | 5/68 | 8/68 | 9/68 | 1/69 | 11/69

News Briefs

News Briefs, September 1966 Radio-Electronics - RF CafeMajor Antenna Breakthrough?

Ever since Marconi stretched a longwire and copied history's first DX, the problem of antenna size versus available space has given engineers and technicians headaches. An antenna which is physically small (compared to wavelength) simply doesn't capture very much signal. Hence its gain is low and it doesn't respond very well to weak signals. For convenience, however, most people prefer small antennas; TV rabbit ears are a good example. Yet such antennas are inefficient.

Major Antenna Breakthrough? - RF CafeThree recent developments could mean a really efficient yet small antenna. Putting an rf preamp at the antenna terminals has been done for some time for a greatly improved signal/noise ratio. But the relatively recent development of inexpensive high-gain rf transistors has made possible a type of antenna which is a combination of active and passive elements. The idea they seem to share is to "marry" transistors to individual antenna elements.

New Type of Small Antenna - RF CafeLate in April the US Air Force revealed what was called a Subminiature Integrated Antenna (SIA). As shown in the drawing, transistors are connected between the antenna elements and the coaxial lead-in. A top hat of capacitance is also connected to a common junction. This hookup makes it practical, it is claimed, to reduce antenna length from 1/4 to 1/50 wavelength and still have reasonable signal pickup. A TV or FM receiver version could be 2 or 3 inches long. Because of the transistor's beta, the SIA has a lower resonant frequency than a passive element alone. Characteristic impedance is close to that of standard coaxial cables, and can be matched by adjusting the transistor transconductance. Bandwidth of the solid-state antenna is greater than that of a passive version. The new antenna can be made in horizontal or vertical configurations, bidirectional or omni-directional.

SIA was developed during a 4-year program by the Air Force. Inventor is Edwin M. Turner of the Air Force Avionics Lab, Wright-Patterson Air Force Base, Dayton, Ohio. He estimates an SIA for TV reception could be about the size of a penlight battery, and could be manufactured for $2 to $3.

An antenna that seems similar was demonstrated at the October 1966 convention of the Audio Engineering Society in New York City. Described as an "omnipolar high-gain vertically polarized antenna of small dimension" it appeared to be a plastic tube about 14 inches long and 1 inch in diameter. Its developer - William S. Halstead, of Multiplex Development Corp. - said that inside the tube was a spiral of wire which formed a monopole antenna element. At the base of the tube (shown at the right in the photo) Halstead stated there was an FET preamp driving the coax back to the receiver.

The Halstead antenna was devised for mobile reception of SCA subchannels from FM stations. It was claimed to have a gain of 4 dB over a reference dipole, with equal response to both horizontally and vertically polarized transmissions. It has maximum response when in a vertical position, and minimum when 45° away from vertical.

In January 1967 the antenna was placed in service on the Eastern Air Lines Air Shuttle run between Washington, New York and Boston. It became part of a system operated by Newsrad, Inc., which furnishes news and weather reports to airline passengers. Tape cartridges containing the newscasts are played in the studios of New York's WOR-FM and transmitted via their SCA subchannel. Signals are then picked up by the Halstead antenna and the Newsrad receiver in a plane just before it lands at LaGuardia Airport in New York City.

In September 1966 several demonstrations of a new antenna were held in the small Ohio town of Lewisburg (near Dayton). The antenna- known as the Americus SkyProbe - was developed by John M. Eagle of UniScience Laboratories, Inc. at Lewisburg. As shown in the photo, the antenna is built inside a plastic tube. In one demonstration, it was connected to a TV receiver with 300-ohm twin-lead and then dropped into the bottom of a metal water well 139 feet deep. Observers reported good reception of vhf TV stations 20 miles away, and fair reception of vhf stations 50 miles away and a uhf station at 20 miles.

Eagle states that his antenna is "not a diapole" [sic], but can receive both color and uhf beneath the earth's surface. He claims that classic theories of TV and radar reception are "incorrect or incomplete"; that the earth's magnetic field carries "video and audio"; and that neither antenna size nor height is a "controlling factor" in reception.

The SkyProbe antenna has been advertised and sold in stores in Ohio. Ads claim it is solid-state, but no further details were available from UniScience.

None of the above cases have shown protection from multipath or ghosting. Each seems to use semiconductor gain to compensate for antenna inefficiency.

Time Signals

Standard frequency and time stations WWV (Fort Collins, Colo.) and WWVH (Maui, Hawaii) are now making voice announcements in Greenwich Mean Time (also known as Universal Time, or UT). The National Bureau of Standards stations thus have joined time and frequency stations in other countries which have been making announcements in GMT for some time.

Low-frequency WWVB (which does not make time announcements in voice) is one of only two stations currently transmitting the internationally recognized unit of time - the atomic second - in a coordinated system. DCF77, at Mainflingen, West Germany, transmits pulses which are synchronized to within 1 msec of those from WWVB. Both stations use the Stepped Atomic Time System; time pulses are one atomic second apart, and carrier frequencies remain constant at their nominal values.

More on Walkie-Talkie Rule Change

As reported in this column in our April 1967 issue, the Federal Communications Commission has proposed to change its regulations governing 100-mW Part 15 transmitters operating in the 27-MHz Citizens band. Chief provision is to move license-free walkie-talkie operation to 5 channels in a band from 49.9 to 50.0 MHz.

If adopted, the new rules would also require the following: frequency tolerance of 0.01 %; total dc power input under any modulation condition not to exceed 100 mW; superregenerative detector in associated receiver prohibited; transmitter must be type approved; certain limitations on spurious emissions.

Present 100-m W operation in the 27-MHz band would be permitted for 7 years following adoption of the new regulations.

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