What is fire or flame made of

“The original carrier signal from the radio station can be modified by the lightning strike. This carrier signal when demodulated by the radio to retrieve the audio signal, produces the undesired noise”

 

A radio set works on the principle of electromagnetic induction. Briefly, electromagnetic induction is the phenomenon in which, time varying electromagnetic field in the neighborhood of a conducting loop induces a similarly time varying electric current in the loop. And as a result, a magnetic field is produced in the conductor’s vicinity.

A carrier signal is generated by the radio station, which is effectively a electromagnetic signal which has frequency in the radio frequency range. Each radio station has a fixed and specific carrier frequency. Now, employing either amplitude or frequency modulation, the signal is modulated with the audio signal. Modulation is the method of addition of information to a carrier signal, which in this case is the electromagnetic signal produced by the radio station.

The antenna of the receiving radio set picks up the electromagnetic signal transmitted from the radio station. Even though all the signals from different radio stations are present in the atmosphere, the radio set has electronic components capable of picking up the desired signal from the atmosphere. The audio signal is retrieved from the carrier signal(demodulation) and further processed by the amplifier to improve its strength. Finally the speakers play out this amplified audio signal.

However the demodulated signal can be affected, if the carrier signal is modified by some means during transmission. And when lightning strikes near a radio set, this is what happens. The frequency range of the carrier signal and the lightning has overlapping frequency ranges, which means a lighting strike in the vicinity of the radio set can alter the carrier signal. 

This adds unwanted noise in the original carrier signal, which when processed by the radio set produces the crackle and pop sounds, thus degarading the quality of the audio.

References


[1] https://en.wikipedia.org/wiki/Modulation

[2] http://www.thehindu.com/todays-paper/tp-features/tp-sci-tech-and-agri/lightning-effect/article2225401.ece

[3] https://th.answers.yahoo.com/question/index?qid=20110702233956AAtA2dk

[4] http://searchnetworking.techtarget.com/definition/modulation

[5] https://en.wikipedia.org/wiki/Carrier_wave

[6] https://en.wikipedia.org/wiki/Demodulation

[7] https://en.wikipedia.org/wiki/Electromagnetic_induction