Transmitters and receivers with antennas
First Claim
1. In combination a single antenna and a transmitter/receiver, the transmitter/receiver comprising a circuit having terminal means designed to transmit and/or receive signals at a predetermined frequency and wavelength in the VHF band and having input/output terminal means and a casing at least part of which is conductive and in which the circuit is located, the casing having a length dimension greater than its dimensions in other directions, the antenna comprising a straight wire portion and a coiled wire portion connected in series and extending in the direction of the length dimension of the casing, at least a majority of the coiled wire portion being exterior to the conductive part of the casing, and in which the straight wire portion and the coiled portion having a combined length which is no more than a quarter of the predetermined wavelength, one end of the coiled wire portion is connected directly to the transmitter/receiver terminal means without the intermission of a transmission line and so as to be substantially rigid with the casing, the coiled portion and the straight wire portion having predetermined lengths to provide a radiated output/received signal at said wavelength greater than the signal given by a straight wire antenna of length equal to said combined length, and the coiled wire portion is a bifilar wire having two parts, an end of each part of which is connected to the straight wire portion, another end of one part of which is connected to the output terminal means of the transmitter and another end of the other part of which is connected to one of the transitter power supply terminals through a blocking inductance.
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Abstract
The invention concerns a combination of a transmitter/receiver (12, 13) having a predetermined frequency/wavelength and an antenna (15), the antenna comprising a coiled wire portion (16) one end of which is connected to the output (14) of the transmitter/receiver and a straight wire portion (17) one end of which is connected in series to the other end of the coiled wire portion, the combined length of the portions being no more than one quarter wavelength, the inductive reactance of the coiled wire portion (16) being selected to both substantially tune out the capacitive reactance of the transmitter (12, 13) and the capacitive reactance of the straight wire portion so that the overall impedance of the system is predominantly resistive, and at least the majority of the coiled portion (16) being external to the conductive portion (12) of the transmitter so as to effectively add to the electrical length of at least the straight portion (17) and itself act as a radiator. The system is particularly designed to be used with no ground plane or only a partial ground plane and with the antenna length less than quarter wavelength. This is particularly useful in the sport of falconry. The system of the invention gives a higher output than a conventional quarter wavelength straight antenna with no ground plane.
48 Citations
18 Claims
- 1. In combination a single antenna and a transmitter/receiver, the transmitter/receiver comprising a circuit having terminal means designed to transmit and/or receive signals at a predetermined frequency and wavelength in the VHF band and having input/output terminal means and a casing at least part of which is conductive and in which the circuit is located, the casing having a length dimension greater than its dimensions in other directions, the antenna comprising a straight wire portion and a coiled wire portion connected in series and extending in the direction of the length dimension of the casing, at least a majority of the coiled wire portion being exterior to the conductive part of the casing, and in which the straight wire portion and the coiled portion having a combined length which is no more than a quarter of the predetermined wavelength, one end of the coiled wire portion is connected directly to the transmitter/receiver terminal means without the intermission of a transmission line and so as to be substantially rigid with the casing, the coiled portion and the straight wire portion having predetermined lengths to provide a radiated output/received signal at said wavelength greater than the signal given by a straight wire antenna of length equal to said combined length, and the coiled wire portion is a bifilar wire having two parts, an end of each part of which is connected to the straight wire portion, another end of one part of which is connected to the output terminal means of the transmitter and another end of the other part of which is connected to one of the transitter power supply terminals through a blocking inductance.
- 2. In combination a single antenna and a transmitter-receiver, the transmitter/receiver comprising a circuit having terminal means designed to transmit and/or receive signals at a predetermined frequency and wavelength in the VHF band and having input/output terminal means and a casing at least part of which is conductive and in which the circuit is located, the antenna comprising a straight wire portion and a coiled wire portion connected in series, at least a majority of the coiled wire portion being exterior to the conductive part of the casing, and in which the straight wire portion and the coiled portion have a combined length which is no more than a quarter of the predetermined wavelength, one end of the coiled wire portion is connected directly to the transmitter/receiver terminal means without the intermission of a transmission line, and the coiled portion and the straight wire portion having predetermined lengths to provide a radiated output/received signal at said wavelength greater than the signal given by a straight wire antenna of length equal to said combined length in which the coiled wire portion has an inductive reactance, the transmitter/receiver casing and the straight wire portion each have a capacitive reactance and the said reactances are selected to tune each other out so that the overall impedance of the combination is resistive.
Specification