La valoración del PIT en la perspectiva de los jóvenes

• The Radio Proximity Fuzes are also called Variable Time (VT) Fuze as the operation time varies with the range of the target. The proximity fuze is a self- contained radio controlled fuze capable of

transmitting waves of radio frequency, and of

receiving a portion of these waves, which may be reflected by the target. The fuze fires when the

returning signal is of sufficient strength, due to

4.4.1 Radio Proximity (PRX) Fuze

• Essentially, the fuze is an extremely rugged radio transmitting and receiving station, which fits into

the nose of a projectile. The Radio PRX fuze may be defined as “A fuze wherein primary initiation

occurs by remotely sensing the presence, distance, and/or direction of a target or its associated

environment by means of a signal generated by the fuze or emitted by the target, or by detecting a

disturbance of a natural field surrounding the target.”

4.4.1 Radio Proximity (PRX) Fuze

• The proximity fuzes are particularly very useful in ground to air and air to ground applications where the probability of hitting the target is less. Using proximity fuze increases the probability of target destruction as now we need to only bring the

ammunition in the vicinity of target and fuze does the rest.

4.4.1 Radio Proximity (PRX) Fuze

(i) Fundamental make-up: The radio proximity fuze

basically consists of an antenna, oscillator/detector, audio frequency amplifier, electronic safety circuit, Power supply, firing circuit and other mechanical safety and arming sub-assemblies. The block

4.4.1 Radio Proximity (PRX) Fuze

(ii) Working principle: Proximity fuzes functions on the

principle of Doppler effect. The Doppler effect states that, if there is a relative motion between two objects then the

frequency of reflected waves would be different from that of transmitted waves. If the two objects approach each other

than the frequency of reflected waves is greater than that of transmitted waves and if they move in apposite direction than frequency of reflected waves is less than that of

transmitted waves. The difference in frequency can be utilized to sense the target.

4.4.1 Radio Proximity (PRX) Fuze

• The working principle of the PRX fuze shown in block diagram is as follows. The power supply is activated only after firing the

ammunition by utilizing setback force. The rest of the circuitry gets the power through safety switch and starts functioning.

4.4.1 Radio Proximity (PRX) Fuze

• The proximity sensor unit (RF oscillator/detector) gets power after a delay as set in ‘Time delay unit’. This is to ensure that proximity sensor gets activated only in the later part of trajectory of projectile and hence reducing any possibility of jamming or influence from other electro-magnetic signals.

4.4.1 Radio Proximity (PRX) Fuze

• The RF oscillator/detector generates the RF waves of required frequency, which are then transmitted by antenna. The radio waves travel at the speed of light in space. These waves will be reflected back to the oscillator by any target that gives a radio reflection, such as metal objects, water, or earth.

4.4.1 Radio Proximity (PRX) Fuze

• The detector receives some of the RF waves reflected from the target. The

transmitted and reflected waves interfere with each other to give a beat frequency. The amplifier circuit amplifies the beat frequency, which is in audio frequency range.

4.4.1 Radio Proximity (PRX) Fuze

• The electronic safety circuit delays the path of power to reach firing circuit and hence delaying the firing condenser to get charged till a certain time is lapsed after firing the ammunition from the gun. This ensures safety during firing of ammunition and avoids any premature functioning of the fuze.

4.4.1 Radio Proximity (PRX) Fuze

• The condenser is charged by power supply voltage before the firing circuit receives signal from audio amplifier, setting safety time in electronic safety circuit much less than the total flight time ensures this. Once the condenser is charged, the projectile is “armed” and ready to detonate when a target influences to do it so.

4.4.1 Radio Proximity (PRX) Fuze

• The output of amplifier is coupled to the electronic switch of firing circuit to trigger the firing mechanism of the fuze. At first the

projectile is so far from the target that the strength of reflected waves and hence output signal of amplifier is too weak to trigger the firing circuit.

4.4.1 Radio Proximity (PRX) Fuze

• As the proximity fuze projectile approaches the target, the amplitude of the beat frequency produced in the detector circuit increases and hence the output of audio amplifier also increases.

4.4.1 Radio Proximity (PRX) Fuze

• When the projectile reaches a specified position relative to the target and hence the output of the audio amplifier reaches a certain level, the electronic switch of firing circuit is closed and the path between firing condenser and electric detonator is completed.

4.4.1 Radio Proximity (PRX) Fuze

• The firing condenser is discharged into the electric detonator dissipating sufficient energy to start the detonation process.