CA1283458C

CA1283458C - Cordless guitar transmitter

Info

Publication number: CA1283458C
Application number: CA000581425A
Authority: CA
Inventors: Richard L. Davis
Original assignee: Airjack Wireless Systems Inc
Current assignee: Airjack Wireless Systems Inc
Priority date: 1988-10-27
Filing date: 1988-10-27
Publication date: 1991-04-23
Anticipated expiration: 2008-10-27
Also published as: EP0366442A2; EP0366442A3

Abstract

ABSTRACT

An electronic device is provided which, when connected to an electric guitar, or other similar stringed instrument, will effect wireless transmission over a selectable frequency of the FM broadcast band.
The unit is compact as it uses the metal strings of the guitar as a partial antenna. The unit remains stationary after being plugged into the guitar's input receptacle, and no transmitting portion of the device has to be attached to the musician's belt or guitar strap, or to the musician's person in any fashion. Furthermore, no large unsightly, cumbersome antenna extends from the device itself. The device is automatically turned on when plugged in.

Description

12834~;8 CORDLESS GUITAR TRANSMITTER

3ackaround of the Invention Electric guitars in common use must ~e connected into special amplifiers by wire. ~s such amplifiers usually requlre household AC current, they cannot be readily taken to places where AC current is not available such as beaches, parks or roadside rest stops, for example. Even if a guitar amplifier could operate by battery power, it would be inconvenient to carry it to a beach or park as well as a portable radio (a radio is standard equipment for beach-goers). A guitar adapted to transmit over FM would reduce the need to carry special guitar amplifiers. Portable FM radios are generally more convenient to transport than guitar amps, and are, in many cases, installed in automobiles.
Although some prior art guitars have built-in amplifiers and speakers, such as the guitar of U.S. Patent 3,781,451, these are special devices as opposed to an add-on component which can be used with a favorite old guitar.
While the prlor art provides cordless electrical guitar systems, there are problems associated with these designs which the present invention overcomes. For example, prior art devlces such as those described in U.S. Patents 3,080,785; 3,085,460; 3,296,916; 3,743,751;
3,825,666 and 3,901,118 require a wire or inconveniently long antenna be attached either to the guitar or to the musician to act as an antenna for the transmitter.
Instability i8 often a problem in these devices as the antenna, which is sub~ected to constant movement while in use, can be affected by external elements such as the musician's body, or other nearby ob~ects of a conductive nature. Further, these external antennae are unsightly 1~83458 and can restrict or impede the musician's choreographic performance.
Another dl B advantage of prior art wireless transmitter systems for guitars is that they usually requlre modlflcation to a guitar, i.e. either the entire system, or a portion thereof must be screwed or taped onto the guitar, for example, generally becoming a rather permanent component of the guitar.
Some prior art wireless transmitter systems for guitars require a special receiver which must, itself, be plugged into a standard gultar amplifier. This, of course, does not solve the problem of the guitarist who wants to ampllfy his music at a park or beach where AC
is not available.
S~mmary of the Invention Accordingly, a transmitter unit for usa with a strlnged musical instrument having a transducer electrically connected to an output jack is provided, said unit comprising transmitter circuitry; a coil of wire or other conductive means connected to said circuitry and adapted to induce a RF pattern with the strings of ~aia muslcal lnstrument, the combinatlon of saia coil or other conductive means and sald strlngs acting as an antenna when the unit is in use; a phono plug adapted to be inserted into said output ~ack, to provlde an lnput to said circuitry from said transducer and to connect said strings to a ground of said clrcultry, sald plug extending from said housing, said housing being adapted to be held in place on sald instrument by said plug; power supply means for providing power to sald circuitry.

Brief Descrlption of the Drawings FIG. 1 is a cross sectional view of a preferred lX834~;8 embodiment of the cordless gultar transmitter device.
FIG. 2 is an electrical schematic diagram of the circuit of the transmltter device shown in FIG. 1.

e~L~ o~ of the Preferred Embodiment The preferred embodiment of the present invention is designed to allow musicians to play an electric guitar or other stringed instrument having a transducer and an output jack, and have it received by any nearby FM radio or FM stereo receiver, without any electrical cord being required to connect the guitar to the radio or receiver.
A wireless system is provided that is fully tunable over the entire FM broadcast band.
The device is a compact transmitter which does not incorporate or require any cumbersome external antenna.
The device of the preferred embodiment is also a structurally self-supporting tran~mitter which is readily detachable from and easily attachable to any standard unmodified electric gultar or other similar ~trlnged lnstrument having a transucer electrically connected to an output jack.
Referring to FIG. 1, the physical layout of the preferred embodlment can be seen.
The complete unlt i8 very compact, being about the si2e of an egg, and remalns generally stationary on the gultar, when inserted, as it plugs directly into the electric guitar's lnput receptacle. It is therefore not necessary to have the transmltting portion of the device attached to the musician's belt or guitar strap; or to have it attached to the musician' 9 person in any fashion.
The power switch means for the unit is somewhat uni~ue in that it has been incorporated in the modified ~" phono plug 19. The plug 19 comprises an upper base portion 14, a first insulating 6pacer 16, a lower base portion 18, a second lnsulatlng spacer 20, and a lower plug segment 22. When the plug 19 is inserted into the guitar' s input receptacle, the batteries 30 are electrically connected to the circuitry 32, which is then energized as will later be explained in more detail.
Removal of the unit from the guitar will effectively turn off the power to the circuit 32 for increased battery life.
The threads 42 of the device allow for the removal of the non-conductive upper casing 10, for easy replacement of batteries 30 which are of the small coin lithium type. Upper circuit board 32 and associated components are physically attached to non-conductive upper casing 10. Plug 19 and associated components are physically attached to non-conductive lower casing 12.
When the upper caslng 10 18 6crewed onto lower casing 12, via threads 42, electrical connection is made between upper circuit board 32 and plug 19 and associated components by way of two small spring connector pins 38 and 39.
Modiflcation of the ~" phono plug 19 for use as a switch has been accomplished by splitting the base portion of plug 19 into two separate portions 14 and 18, and electrically separating them by an insulating spacer 16. The spacer 16 is oonstructed of a non-conductive materlal such as plastlc. Upper base portlon 14 is electrically connected to the negatlve terminal of batteries 30 placed in serles, while the lower base portlon 18 is connected to one of the small spring connector pins 38. The other spring connector pln 39 is connected to lower plug segment 22, which allows the pick-up of the guitar to be connected to the circuit, thus provldlng audio lnput to the device. These connections to plug segments are made via internal plug connectors 24. The plug base portions 14 and 18 have been separated by first insulating spacer 16 at an angle, as seen in FIG. 1, 80 that the unlt will work effectively in different types of guitars, some of which have input receptacles dlffering from standard depth, to provide proper connection of the two segments when the device is in use.
The positive terminal of batteries 30 placed in series is connected to the unit~s circuitry via upper battery connector 36. The batteries 30 are insulated from spring connector pins 38 and 39 by way of a plastic sleeve (not shown) which can be attached to the upper surface of lower cirouit board 26, or to the lower surface of upper circuit board 32.
The transmitting frequency of the device can be ad~usted to any frequency in the FM broadcast band (88 to 108 MHz) by adjusting a small ferrite core in tuning inductor 34, which forms a part of the circuit of upper circult board 32, via tuning aperture 30 located at the top of upper caslng lO.
Most electronic components of the transmitter are surface mounted on the upper surface of upper circuit board 32. A small input capacitor Cl (see FIG. 2) is located interior to lower casing 12 (FIG. 1). Referring to FIG. 1, when the unit is manufactured areas surrounding internal plug connectors 24 and tuning inductor 34 are filled with a non-conductive resinous material for stabllity and durability.
Referring now to FIG. 2, a circuit diagram of the transmitter can be seen. The electronic circuit of the unit is based on a modified version of a Colpitts oscillator.
By including a length of wire 50 in the circuit, separate from, but electrically connected to the tank circuit 45, and wrapping it around the components of the upper circult board 32 (see FIG. 1), R.F. radiation can be induced between the strings of the guitar and the lZ83458 length of wlre S0, when the device is in use. There is no movement of the colled length of wlre 50 as its posltion ls fixed ln the unlt~s houslng, resulting in excellent freguency stablllty. As the strings of the guitar are normally connected to ground, they act as a ground plane, or an element of the device' 9 antenna to greatly increase the effectlve range of the unit when it i8 ln use. No external antenna is requlred, resultlng in compactness of the unit. The resultant transmltting range of the devlce 18 very high, in the order of 100 feet, and the signal is remarkably strong and stable. As there are no movable cords, wires or external antennas emanatlng from the device or attachlng lt to the guitar, the effectlve antenna remalns stationary relatlve to the gultar for stabillty of slgnal, whlch could be affected by movement or changes ln statlc capacltance or lnductance between a movable cord, wire or external antenna and a musician, lf a cord, wire or external antenna were used.
The clrcuitry does not re~uire any audlo pre-amplification stages as the change ln current produced by the change of impedance of the guitar~s own transducer adequately modulates, by lmpedance, the baslc RF carrler of the osclllator.
The upper and lower casings 10 and 12 of the unit, as shown in FIG. 1, are produced from plastic or any appropriate materlal. It 18 ln this housing that all components of the circuit, clrcuit boards 26 and 32, batterles 30 and connectors 24, 28, 36, 38, 39 and wlre coll S0 (see FIG. 2) whlch acts ln co-relation wlth the guitar strlngs are contained. The only part external to the casings is the modified ~" phono ~ac~ 19 (see FIG. 1) which emanate6 from the base of the lower casing 12 and which plugs dlrectly into the gultar when the unlt is to be used.

lX834~8 Referring to FIG. 1, an appropriate voltage for series batteries 30 would be 6 volts DC.
Referring to FIG. 2, appropriate values for R1 and R2 would be 47K ohms and 470 ohms, recpectively; these values have been determined to be of an appropriate ratio to properly bias the partlcular transistor used, and to allow low power consumption. Appropriate values for C2, C3 and C4 would be 0.001 Mfd, 4.7 pf, and 4.7 pf, respectively; an approprlate value of filter capacitor C
would be found in the range of 1 to 10 Mfd; an appropriate tuning inductor 34 would be adjustable to lOmH; and an appropriate transistor Q1 would be a Sylvania type ECG 107, npn Si VHF, IF, RF, Amp, OFC
transistor.
Several possible modifications of the preferred embodiment will be apparent to those skilled in the art.
For example, the values of resistors R1 and R2 could be varied, and the transistor used could be changed, as long as the resistor values are chosen to properly bias the particular transistor used. The values of C3 and C4 could be varied; however, this may result ln the unit being tunable over only part of the FM band. A Hartley oscillator could be substltuted for the Colpitts osolllator, ln fact any appropriate RF oscillator could be used. Further, the colled length of wire 50 (see FIG.

2) could be replaced wlth a metallic coating of the interior or exterior of the upper or lower casing 10 or 12. Although stabillty 18 maintained when such a coating is used, range is significantly reduced.
While the preferred embodlment has been dlsclosed with certain given parameters, obvious modifications to the circuit or to the given parameters will become apparent to those skilled in the art, and the protection sought should be llmlted only by the spirit and scope of the appended claims.

Claims

1. A transmitter unit for use with a stringed musical instrument having a transducer electrically connected to an output jack said unit comprising a housing containing transmitt-er circuitry;
a coil of wire or other conductive means connected to said circuitry and adapted to induce a RF pattern with the strings of said musical instrument, the combination of said coil or other conductive means and said strings acting as an antenna when the unit is in use;
a phono plug projecting from said housing and adapted to be inserted into said output jack, to provide an electrical input to said circuitry from said transducer and to connect said strings to a ground of said circuitry, said housing being adapted to be held in place on said instrument by said plug;
power supply means for providing power to said circuitry.

2. The unit of claim 1 wherein said transmitter is adapted to transmit at a radio frequency.

3. The unit of claim 1 wherein said transmitter is adapted to transmit at a user adjustable frequency within the FM
band.

4. The unit of claim 1 wherein a portion of said plug comprises two electrically separate parts which when connected by insertion of said plug into said jack completes a circuit to turn on said circuitry.

5. A transmitter unit for use with a stringed musical instrument having a transducer electrically connected to an output jack, said unit comprising:
a lower housing containing a lower circuit board;
a phono plug extending from said lower housing;
an upper housing detachably mounted to said lower housing, said upper housing including an upper circuit board;

said upper circuit board being adapted to be electrically connected to said lower circuit board by connector pins when said upper housing is mounted to said lower housing.
power supply means;
said upper and lower circuit boards being electrically connected to said power supply means and to said phono plug to comprise said transmitter circuitry for said transmitter, an output of said circuitry leading to a conductive radiator means.

6. The unit of claim 5 wherein said upper housing is threadedly mounted to said lower housing.

7. The unit of claim 5 wherein said power supply means comprises at least one battery.

8. The unit of claim 5 wherein said plug comprises an upper base portion, a lower base portion and a lower plug portion, said lower plug portion being adapted for electrical connection to a portion of a jack of said guitar that can provide a musical signal from said guitar to said transmitter circuitry.

9. The transmitter of claim 8 wherein said upper base portion and said lower base portion are adapted for electrical connection to a portion of said jack that can provide a ground for said transmitter circuitry.

10. The unit of claim 8 wherein said upper base portion is electrically connected to said lower base portion when said plug is inserted into said jack, to electrically complete said circuitry for said transmitter.

11. The transmitter of claim 5 wherein said electrical connections between said phono plug and the remainder of said circuitry for said transmitter are made interior to said lower and upper housings.

12. The transmitter of claim 5 wherein said circuitry of said transmitter leads to a coil of wire.

13. The transmitter of claim 12 wherein said circuitry of said transmitter comprises an appropriately adapted RF, frequency modulated, oscillator.

14. The transmitter of claim 12 wherein said circuitry of said transmitter comprises an appropriately adapted Colpitts oscillator.

15. A transmitter for an electric guitar comprising:
transmitter circuitry comprising an appropriately adapted Colpitts oscillator, said circuitry being adapted to transmit at a user selectable frequency within the FM band;
housing surrounding said circuitry;
a coil of wire connected to the output of said circuitry;
a phono plug for use with a standard electric guitar jack, said plug extending from said housing, said housing being adapted to be held in place on said guitar by said plug;
said phono plug comprising a base portion and a lower plug portion, said lower plug portion being adapted for electrical connection to a portion of said guitar jack that is electrically connected to a transducer of said guitar to provide an electric-al input to said circuitry, and said base portion being adapted for electrical connection to a portion of said guitar jack that is electrically connected to said strings of said guitar to provide a ground for said circuitry;
said strings being electrically connected to ground when said guitar is in use.

16. A transmitter unit for use with a stringed musical instrument having a transducer electrically connected to an output jack, said unit comprising:
a housing containing transmitter circuitry and a coil of wire or other conductive means connected to said circuitry and adapted to induce a RF pattern with the strings of said musical instrument, the combination of said coil or other conductive means and said strings acting as an antenna when the unit is in use;
a phono plug projecting from said housing and adapted to be inserted into said output jack to provide an electrical input to said circuitry from said transducer and to connect said strings to a ground of said circuitry, said housing being adapted to be held in place on said instrument by said plug;
power supply means contained in said housing for providing power to said circuitry.

17. The unit of claim 16 wherein said transmitter is adapted to transmit at a user adjustable frequency within the FM
band.

18. The unit of claim 17 wherein said transmitter circuitry comprises an appropriately adapted RF oscillator.

19. The unit of claim 17 wherein said transmitter circuitry comprises an appropriately adapted Colpitts oscillator.