US 3324473 A
Description (OCR text may contain errors)
R. A. FLEMING 3,324,M3
LINE CORD ANTENNA Filed Aug. 24, 1965 RADIO CIRCUITS INVENTOR'. RODNEY A. FLEMING.
3,324,473 LINE CORD ANTENNA Rodney A. Fleming, Frankfort, N.Y., assignor to General Electric Company, a corporation of New York Filed Aug. 24, 1965, Ser. No. 482,084- 2 Clairns. (Cl. 343720) This invention relates to line-cord antennas for radios and the like.
Various ways have been devised for using the power line cord of a radio as an antenna, especially for FM reception. The antenna input terminal is coupled, capacitively or inductively, to one or both wires of the radios power cord. For example, a third wire has been added alongside the two wires of the power cord to provide a capacitive coupling to the power wires, this third wire being connected to the antenna input terminal of the radio. Also, other capacitive couplings have been employed, such as a capacitor connected between a powercord wire and the antenna terminal, or a metal clip or clamp positioned against or around the power cord and connected to the antenna terminal. Any such capacitor must, of course, have a high enough voltage rating for safe use with respect to the power line voltage. All of these prior systems add to the cost of manufacturing radios.
An object of the invention is to provide an improved power-line antenna.
Another object is to provide a low-cost power-line antenna.
A further object is to provide a capacitive-coupled power-line antenna which does not require the use of a high-voltage capacitor.
Additional objects will be apparent from the following description and claims, and from the accompanying drawing.
The line-cord antenna of the invention comprises, briefly and in a preferred embodiment, circuitry having an antenna terminal, a power transformer for providing power to the circuitry from a power source via a line cord and having a core assembly associated with a winding arrangement, and means connecting the core assembly to the antenna terminal, whereby the core assembly provides a capacitive antenna coupling to the line-cord wires. Preferably a capacitor of small capacitance value, and which may have a low voltage rating, is connected between the antenna terminal and the core assembly of the transformer.
The single figure of the drawing shows a preferred embodiment of the invention.
Radio circuits 11, indicated generally in block form and which may comprise conventional radio-frequency circuits, include an antenna terminal 12 and a ground terminal 13. These terminals may, if desired, comprise screws or other means for connecting external antenna and ground wires. The radio circuits 11 may be mounted on a printed-circuit board or on a metal chassis.
A power transformer 14, which may be conventional, comprises a winding arrangement 16 positioned on a metal core 17 which is held in place by a metal frame or housing 18 provided with mounting tabs 19 having openings 21 for accommodating rivets or other means for attachment to a circuit board or cabinet. If the transformer is mounted on an electrically grounded metal chassis, it should be electrically insulated therefrom for the purposes of this invention.
A power cord 22 extends from a primary winding of the transformer 14, and extends externally of the radio and is provided with a plug 23 for attachment to an electrical power outlet. Wires 24 are connected between a secondary Winding of the transformer 14 and power terminals 26 of the radio circuits 11.
The antenna terminal 12 is connected to the transformer frame 18, either directly, or via a capacitor 27 as shown. Since the frame 18 and core 17 are inherently capacitively coupled to the wires of the line cord 22 via the winding arrangement 16, the antenna terminal 12 is capacitively coupled to the line cord wires, thus providing line-cord antenna performance as good as or better than other types of line-cord antennas. Of course, the frame 18 should not be connected to other points in the circuits 11 which would impair the antenna performance.
The capacitance between the core assembly and the line cord of the transformer 14 is usually considerably greater than required for the antenna coupling, and hence the use of a small capacitor 27 is sometimes preferred to a direct connection from the antenna terminal 12 to the transformer frame 18, because it reduces electrical loading by the line cord on the antenna input circuit and thus permits the use of an external long-wire antenna connected to the antenna terminal 12 if desired. Also, the use of the capacitor 27 tends to improve the intermediate-frequency rejection of the radio circuits. The capacitor 27 can be an inexpensive capacitor of low capacitance value (10 micromicrofarads, for example) and very low voltage rating since no appreciable voltage is applied across it. The capacitor 27 may be omitted, and the antenna terminal 12 may be connected directly to the frame 18, if the radio circuits 11 have good intermediate-frequency rejection and it is not desired to provide for the use of an external antenna.
The frame 18 either inherently makes electrical contact with the core 17, or else provides sufficient capacitive coupling thereto, for the purposes of the invention. The same applies to a fully-enclosing type of transformer frame or housing, which also would provide capacitive coupling directly to the winding 16. If desired, the antenna connection can be made from the antenna terminal 12 to the core 17, or to rivets or screws holding the core together. Thus, the term core assembly as used herein means, broadly, not only the core 16 but also includes any frame 18 or other metal support means associated with the core.
From the foregoing it will be clear that the invention provides an effective line-cord antenna for FM radios or the like, without incurring the cost of adding any extra components, or, at most, by adding only an inexpensive low-capacitance, low-voltage capacitor.
While a preferred embodiment of the invention has been shown and described, other embodiments and modifications thereof will be apparent to persons skilled in the art and will fall within the scope of invention as defined in the following claims.
1 2. A line-cord antenna arrangement as clalmed in claim 1, including a capacitor interposed between said conductive means and said antenna terminal.
References Cited UNITED STATES PATENTS Grismore 179-2.5
Reid 343905 Brough 343--856 Spindler 343-856 ELI LIEBERMAN, Primary Examiner.
HERMAN KARL SAALBACH, Examiner.
R. HUNT, Assistant Examiner.