Introduction of Heinrich Hertz Spark Gap

Heinrich Hertz Sparrk Gap is the experiment that was first performed by the German scientist whose name was Heinrich hertz and so the experiment is famous after his name. He has experimentally proved the electromagnetic waves existence in 1888. He was born in Germany. In 1880 he got PHD degree from the Berlin University and after that he become a lecturer of physics in University of Kiel then after this in 1885 he has discovered the electromagnetic waves and in 1888 he has proved the Maxwell theory of electromagnetism through the help of experiment. There are some inventions that have been proposed by this scientist that include the Radar, Dipole antenna, Wireless telegraphy and Radar transmitter. His major contribution was in the field of electromagnetism and also in the field of optics.

Heinrich Hertz Experiment

In 1888 Heinrich Hertz gave the electromagnetic theory through the use of experiment that has been mathematically proved by the famous Physician Maxwell. This experiment was based on electromagnetic phenomenon that is when you isolate the electric charge so this charge radiates the electromagnetic waves. This is because when the electric charges are isolated so these charges exert kinetic energy. This kinetic energy is due to different oscillating charges.

Source: http://www.physics.usyd.edu.au/teach_res/hsp/u7/t7_hertz.pdf

Components and Equipment for the Experiment

The equipment that are used for performing this experiment are as follows

·         Permanent Battery of about 3 volts

·         A switch for turn on and off

·         Induction coil

·         Leyden Jar

·         Receiving Loop

The experiment has been performed through the help of two electromagnetic plates and these plates are at some distance to the other plate means to say that these two plates are at 60 cm apart from each other. These two plates also act as the capacitor with very low capacitance value. These two metal plates are connected through the help of two polished copper metal strips with small diameter. The distance between these two metal strips is so much low that is about 2 to 3 cm. These two copper metal strips can be named as M1 and M2.

Through the use of induction coil when the potential difference is applied on the induction coil and then high potential difference is applied at the two ends of the gap that is at M1 and M2, then after this when there is high potential difference between them the air between these gaps gets ionized and as a result it provides a path for the electrons to move in different direction. Due to the ionization of air high spark is produced between this gap and due to kinetic energy the high frequency electromagnetic waves are produced. Then these waves move from the gap toward the receiving coil and this coil is able to receive high frequency electromagnetic waves.

The electromagnetic waves have the frequency of about . In this experiment the two plates A and B are act as the capacitor plates and these copper metal strips are acting as the inductor with very low inductive value.

Between these two metal plates high oscillation frequency is measured through the help of this formula that is given by

In the above equation L is the inductance of the coil, c is the capacitance of the two metal plates.

History of Spark Gap Transmitter

The German scientist in his experiemnt used the Spark gas transmitter. It is one of the first types of transmitter that has been used today. This transmitter was made through sparking that has been done through the spark gap in the transmitter that why this transmitter is called as the spark gap transmitter. There are many applications of these spark gap transmitter that include board ships that was the first means that is used to communicate at long distance.

Source: https://www.electronics-notes.com/articles/history/spark-gap-transmitters/history.php

Spark gap transmitter developed

The next stage in the historic development of the spark gap transmitter was to make this technology capable for the communication in a practical manner. Although many people believe that the radio is not the invention of Marconi as there were many other people who were involved in the developing process of the radio technology. The German scientist had done a lot to make the radio enable to be used in an applied and useful way. So it has been stated many times that in the developing process of radio technology Marconi was not the only person who struggles to make the spark gap transmitter happen. There were also numerous names from whole world who were involved and willing to make this technology in a practical manner like Ferdinand Braun who was from Germany, Popov in Russia and Tesla in United States [1].

More spark gap transmitter innovation

Furthermore it has been said that Marconi was successful to transfer the message crossway to the Atlantic, Marconi had developed an advance technology but it cannot be considered the peak use of this technology as by more developments it is possible to make spark gap transmitter more innovative which can operate with huge success [2].

The primary issue in the production of spark transmitter was it needs to reoccur after the every spurt of oscillation and the reason behind this issue was its circuit of antenna which feedback the dynamism. Due to this spark the signal perform in a change frequency. So it was essential to have a way for spark quenching [3].

By considering this problem there was several ideas which had implemented:

·         Thomson’s magnetic blowout:  In the era of 1890 Elihu Thomson had introduced an idea that by apply the required timely magnetic field at spark transmitter by right direction problem can sort out.

·         Air blast:  this idea was also introduced in the duration of 1980 according to it spark can blow by smearing a time air blast on it.

·         Rotary spark gap: In the era of 1896 rotary spark gap method was introduced by Nicola Tesla which gives an idea that by using a rotary spark gap that is connected with alternator to empower the transmitter. When the alternate voltage had been on peak it will enable the transmitter be matched with time.

The one another problem in developing the spark gap transmitter was that there was very small number of people which accurately understood the transmitters operations. In the duration of 1906 a paper was published in Danzing Germany by Professor Max Wein in that paper he explained all his findings about the mechanism which are used to generate the signals of radio with the help of spark transmitter [4].

The primary issue which was recognized by Wein explained that the use of long spark was not essential to regulate the powerful signals of radio. He further explained that by using a close coupling among the antenna circuit and the spark circuit it can be possible to produce frequency in signal and to generate a high level of efficiency [5].

Spark gap transmitter is overtaken

While the developing and operating and improving of spark gap transmitter had taken place on very high degree as it cannot be compere and contend with transmitters which use valves to generate frequency signal. Integrally spark gap transmitter is considered a wide band and there are significant improvements which take place in its design but it cannot compare the effectiveness and efficiency to those valves based equipment [6].

As outcome in the period of 1920 their use becomes lesser with the time but they engaged for several years as a use for communication in emergency situations by distress frequencies but gradually their use banned as they create interference [7].

It is of great importance to understand the working phenomenon of the core element before studying the function of the spark gap transmitter. Having an idea about the core element and its function will makes it very easy for us to understand the functional characteristics of the spark gap transmitter. [8]

To properly understand the importance of the function of circuit, it is very important to have good idea about the role of the spark gap. Though the function of the spark gap looks to be very simple, yet it is of high importance. In early years when the technology was newly developing, the engineers spent ages to understand the mechanism of action of spark gap and after this they understand the best of transmitters.  [9]

Basically the spark gap works as a switch in transmitter. Initially the spark provides open circuit with great resistance. But after the increase in the voltage across spark gap at a certain point the spark fires, at that point the spark can easily be seen. And at that specific point spark gap becomes ionized. [6] .

Initially spark gap provides great resistance in the circuit but spark gap needs high voltage to show spark. As the voltage start to increase the resistance start to decrease, and at that point when the spark gap shows the spark the resistance decrease to up to 2 ohms only.

Source: https://www.electronics-notes.com/articles/history/spark-gap-transmitters/operation-how-does-spark-gap-transmitter-work.php

 The actual and foremost function of the spark gap is to provide high voltages without being burn out itself. Earlier then engineers have tried many different materials including the induction coils but these materials failed to survive under the stress of high voltages and burn out. After years of experiments and hard work engineers came to know the use and role of spark gap transmitters.

If we analyze the spark gap, we come to know that it is very difficult to predict about the reaction of the spark, one can only guess the right pattern of the breakdown. And the voltage across the spark is very uncertain and varies too much.

All the experiments and years of experience have come to conclusion that spark provides wide range of radio frequencies which can be use effectively in the spark gap transmitters.

Spark is not that efficient to provide radiating signals. It is due to its highly unpredictable sequence of spark and high but unstable voltages across the spark gap. It is one of the major limitations of the use of spark gap transmitters.

 Spark gap transmitter improvements

In the early days after the development of the phenomenon of spark gap transmitters,

The biggest problem was that, these spark gap transmitters cannot accommodate high voltage across them. It was due to continues fire of the spark when the key was down or depressed. At that time the induction coils were used to produce spark. And induction coil only manages 100 mA across the spark gap. These low voltages mean that the signal which produced due to this spark is very low.

Some engineers at that time manage a different method to increase the voltage across the spark, by increasing the distance between two interacting electrodes. This method helped to increase the voltages across the spark but this method was very dangerous for the operators.

References of Heinrich Hertz Spark Gap