Radio Transceiver Dimmer Switch

This invention relates to means for protecting transceivers from high energy radio signals and, more particularly, to a simple, reliable and economical means to perform the same.

Radio transceivers which operate at frequencies commonly known as "citizens-band" have become very popular in that a mobile unit has been installed in many automobiles, trucks, and other moving vehicles. Most transceivers on today's market have an inherent drawback in that if the incoming signal is very strong, the transceiver may be damaged by the signal. The transceiver then must be repaired. Mobile units are more prone to this mishap than base or stationary units because two mobile units on the same channel could, at times, come very close together. For example, as when one vehicle passes another on a highway. Elementary physics explains that the wattage received by a unit is inversely related to the cube of the distance between the transmitting unit and the receiving unit. Then one can see that when a unit is transmitting more power than allowed by the FCC, another unit that is receiving is very likely to be damaged.

An object of this invention is to provide a means in a coaxial cable leading from a transceiver to an antenna, which means bypasses some of the incoming power from the transceiver.

Another object is to provide a means that also limits transmission while limiting incoming power.

Another object is to provide a light in combination with the above means so that the light is only visible whenever the unit is transmitting, indicating that the means is in the limiting incoming power position.

These and other objects and features of advantage will become more apparent after studying the following description of the preferred embodiment of my invention, together with the appended drawing.

The sole FIGURE is a schematic showing my novel means coupled between two lengths of a coaxial cable.

Referring to the drawing, there is shown a standard radio transceiver 11 connected to a standard aerial 12 by standard coaxial cable 13. My invention consists, primarily, of cutting the coaxial cable 13 at a convenient place and inserting my novel means 14 therebetween. Although the drawing shows means 14 schematically, one skilled in the art could readily package it into a convenient sized box shown by dash lines 16, which box is shorted to the outer conductor of cable 13.

The means 14 consists of a double pole which, having an arm 15, connected to a center conductor 17, which is, in turn, coupled to the transceiver. The switch has two poles, 21 and 22, wherein pole 21 is connected to a center conductor 22 which is, in turn, coupled to the antenna 12 and wherein pole 22 is connected in series with a light bulb 25 and the outer conductor 26 of the coaxial cable. Center conductors 17 and 22 are coupled together by a resistor 28. In the prototype the value of resistor 28 was, for example, between 5000 to 8000 ohms and the light bulb was chosen as a standard 6-watt 12-volts bulb.

In normal operation, the switch is thrown so that arm 15 contacts pole 21 and one, by following the circuit, observes that bulb 25 and resistor 28 are both out of the circuit. In the protection mode of the operation wherein one desires to limit the incoming power and inherently limits to outgoing power, the switch is thrown so that the arm 15 contacts pole 22. By tracing the circuit, one finds that the resistor 28 is in series with both center conductors 17 and 22 and lamp 25 is connected across conductor 17 and 26. Therefore, in transmitting, some of the transmitted power is consumed in the lamp 25 whereby it could glow. Lamp 25 is preferably of the non-inductive type so as not to interfere with antenna matching. The rest of the power is conducted by resistor 28 to conductor 26 and antenna 12. Incoming signals are shunted across series circuit consisting of resistor 28 and lamp 25, which form a voltage divider circuit. The center conductor 17, being connected to arm 15 and pole 22, sees only the divided fraction of the voltage signal and couples it to the transceiver 11. My novel means also has an additional advantage besides protecting the transceiver from high incoming power, i.e., when the unit is in the protective mode, the CB unit can be used in close quarters such as campgrounds. This prevents interference with units that are, for example, more than 1/8 mile from the transmitting unit.

Having described the preferred embodiment of my invention, one skilled in the art, after studying the preferred embodiment, could devise other embodiments without departing from the spirit and scope of my invention. Therefore, my invention is to be considered as limited only by the scope of the appended claims.