ELECTRONIC FREQUENCY MODULATOR The present invention relates to an electronic frequency modulator of the type wherein a lower band frequency is transmitted on a carrier wave being an upper band frequency. The present invention has particular application in its use as an electronic scarecrow, however it will be apparent to those skilled in the art that the present invention is of wider application as a deterrent to animal and insect crop pests, and is not therefore to be li itively construed by the following detailed description of its use as an electronic scarecrow.

In Australia considerable damage is done to crops and in particular orchards by flying foxes (fruit bats) and birds which descend and devour or damage fruit prior to harvest.

In _f an average orchard of ten acres containing between three and four thousand fruit trees it is not uncommon for, from two to three million flying foxes, to descend on the orchard and completely devastate the fruit crop and even to break the secondary growth on the trees all within a time span of half an hour.

In order to prevent such destruction of crops, orchardists and growers presently use nets, electric wires and guns in ^' an effort to at least save some of the crop.

These three presently used methods are only partially effective as both electric wires and guns are activated on a periodic cycle and the birds or bats soon learn when the deterrent is non-activated and netting of large areas of orchards or crops is both labour intensive and inefficient in coping with the extreme numbers of birds or bats that can descend on a crop or orchard. The present invention seeks to substantially overcome or at least ameliorate to a great extent the above disadvantages.

In one broad aspect there is provided an electronic frequency modulator which combines a lower band frequency with an upper band frequency to produce a square wave

output on transmission from a transducer, preferably a peizo ceramic.

In a further aspect of the invention there is provided a method of protecting crops from crop pests using an electronic frequency modulator which combines a lower band frequency with an upper band frequency to produce a square wave output on transmission from a transducer, preferably a peizo ceramic.

The present invention generates acoustically pressurized air waves which affect the muscular and skeletal structure of the bird or bat in flight and the unpleasant sensation causes the bird or bat to divert its flight path to avoid the effect.

Whilst sonic and ultrasonic devices are known and - have been tried in the past as a deterrent against birds and bats, they have proven ineffective because the bird or bat soon realises that it is only a noise and there is nothing physical preventing them from feeding.

Through lengthy trials it was discovered that only a specific modulated frequency corresponding with the bird or bat's wing beat would give an unpleasant effect causing the bird or bat to divert its flight path and avoid the effect. It was found that within certain species not every member of that species would be affected by the one modulated frequency.

The ultrasonic frequency effective in controlling crop pests was found to lie within the following ranges. marsupials 10 - 25 KHz birds 15 - 35 KHz insects 40 - 80 KHz

Models are presently available for the specific applications as set out below.

LOWER BAND UPPER BAND FREQUENCY FREQUENCY MODEL CROP PEST INFRASONIC ULTRASONIC

CPS KHZ

815 Crows, galahs, 1-400 17-30 cockatoos

LOWER BAND UPPER BAND

FREQUENCY FREQUENCY

MODEL CROP PEST INFRASO IC ULTRASONIC CPS KHZ

825 Starlings, 1-200 25-40 leathernecks, parrots (certain varieties only)

835 Sheep, cattle, 1-100 20-25 kangaroos, pigs

845 Flying foxes, 1-350 20-25 cormorants, pelicans, dogs, egrets, night herons, ducks 855 Rabbits, mice, 1-50 18-30 white tail rats, possums, wombats The present invention will now be described by reference to a preferred embodiment which is illustrated in the attached drawings in which Fig. 1 is a schematic view of the preferred embodiment in use as an electronic scarecrow.

Fig. 2 is a circuit diagram of the electronic circuitry of the embodiment of Fig. 1.

The electronic scarecrow shown in Fig. 1 is used in a ten acre paddock and is designed to withstand extremes of weather and the normal handling of orchardists and farmers. The electronic scarecrow can be run either continuously or can be preset with a programmable timer to only operate when the crop pests are most prevalent. For larger operations several devices as shown in Fig. 1 can be spaced throughout the orchard or farm.

In Fig. 1 the commercial electronic scarecrow comprises a plurality of known transducer heads 1, mounted on a support column 2 by means of adjustable

mount 3. The support column 2 is stayed to the ground by conventional stays 4 supported on plate 5 on support column 2.

A power supply in the form of a battery 6 is connected to the power pack 7 containing the electronic timer switch, battery level indicator and circuitry as detailed in Fig. 2.

The components as above listed in Fig. 1 with the exception of the circuitry of Fig. 2 are all known and available components.

In Fig. 2 the circuitry comprises the following known electronic components: COMPONENT LIST R15 10 ohm 1/4 w resistor Rl 10 ohm 1/4 w resistor

R22 10 ohm 1/4 w resistor R28 220 ohm 1/4 w resistor R26 ' 470 ohm.1/4 w resistor • R14,29,5 IK 1/4 w resistor R18 1.2K 1/4 w resistor

R23 from IK to 150K fixed component depending on unit, refer to data sheet Rll 4.7K 1/4 w resistor R6 4.7K 1/4 w resistor R24 220K 1/4 w resistor R10 68K 1/4 w resistor R30 470K 1/4 w resistor R27 470K 1/4 w resistor R9 560K 1/4 w resistor R20 1M w resistor

R3 1.2M 1/4 w resistor

R21 1.5M 1/4 w resistor R2 1.8M 1/4 w resistor

R17 5.6M 1/4 w resistor R4,12 110 ohm 1 w resistor

R25 0-25K depending on data sheet attached R8 0-lOOK depending on data sheet attached R19 0-50K depending on data sheet attached R16 2.7K 1/4 w resistor

R7N Not part of main circuit board 3.3 ohms 5 watt

R13N Not part of main circuit board 3.3 ohms 5 watt

C8 TL .001 Ceramic 50V

C2 TL 470 Ceramic 50V C3 NL .001 G cap 100V

C4 TL .01 Ceramic 50V

C5 TM .1/50 Monobloc X5V low profile

Cl TM .1/50 Monobloc X5V low profile

C6 NL .01 G cap 100V C7 NL .01 G cap 100V

D2 IN 914A-P

Dl IN 914A-P

IC1 555 chips IC2 LM3900 chip IC3 566 chip

TIN 2N3055

T7N 2N3055 T6 2N2907A-M

T9, 3, 2 BSW64 T4 DS 557

T8, 2 GED44C8

The present invention is a combination of two frequencies, an upper and a lower band frequency modulated together to produce an FM effect on transmission from a piece of peizo ceramic.

The lower band frequency, referred to as infrasonic frequency, is produced through a linear ramp in a 555 IC working as an astable operation which when triggered produces a pulse applied to an IC LM 3900 (op-amp) producing a staircase generation system which ramps down from a 12 volts. A zena diode Dl supplies the offset and prevents pin 5 of the 566 chip approaching the 12 volt locking up the ramp output of T5 producing a linear range of sweep voltage. The IC3 roduces a s uare wave out ut in the form

of an FM signal which is applied to T9 via pin 3 of IC3 in the required ultrasonic frequencies. The combination is then applied to a common output amp configuration of known circuitry type. The infrasonic signal is to be at the same pulse length as the bird's wing beat. Any alteration to that frequency will have little effect on controlling of birds.

It will be apparent to those skilled in the art that the combination of an infrasonic pulse frequency modulated with an ultrasonic pulse and used as a deterrent for crop pests is unique; and modifications both to the design of the transmitter and the circuitry may be made without departing from the scope of the present invention.