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  2. Spread spectrum - Wikipedia

    en.wikipedia.org/wiki/Spread_spectrum

    Moreover, for a given noise power spectral density (PSD), spread-spectrum systems require the same amount of energy per bit before spreading as narrowband systems and therefore the same amount of power if the bitrate before spreading is the same, but since the signal power is spread over a large bandwidth, the signal PSD is much lower — often ...

  3. Mortimer Rogoff - Wikipedia

    en.wikipedia.org/wiki/Mortimer_Rogoff

    Mortimer Alan Rogoff (May 2, 1921 – August 1, 2008) was an American inventor, businessman, and author as well as an amateur photographer and radio operator. He is recognized for his work in spread spectrum technology which is the technology that modern cell phones and GPS systems are based on. He is also considered the grandfather of the ...

  4. Science fair - Wikipedia

    en.wikipedia.org/wiki/Science_fair

    A science fair or engineering fair is an event hosted by a school that offers students the opportunity to experience the practices of science and engineering for themselves. In the United States, the Next Generation Science Standards makes experiencing the practices of science and engineering one of the three pillars of science education.

  5. Direct-sequence spread spectrum - Wikipedia

    en.wikipedia.org/.../Direct-sequence_spread_spectrum

    Direct-sequence spread-spectrum transmissions multiply the symbol sequence being transmitted with a spreading sequence that has a higher rate than the original message rate. Usually, sequences are chosen such that the resulting spectrum is spectrally white. Knowledge of the same sequence is used to reconstruct the original data at the receiving ...

  6. Code-division multiple access - Wikipedia

    en.wikipedia.org/wiki/Code-division_multiple_access

    CDMA is a spread-spectrum multiple-access technique. A spread-spectrum technique spreads the bandwidth of the data uniformly for the same transmitted power. A spreading code is a pseudo-random code in the time domain that has a narrow ambiguity function in the frequency domain, unlike other narrow pulse codes. In CDMA a locally generated code ...

  7. History of amateur radio - Wikipedia

    en.wikipedia.org/wiki/History_of_amateur_radio

    Some of the problem came from amateurs using crude spark-transmitters that spread signals across a wide part of the radio spectrum. [1] In 1912 after the RMS Titanic sank, the United States Congress passed the Radio Act of 1912 [ 8 ] which restricted private stations to wavelengths of 200 meters or shorter (1500 kHz or higher). [ 9 ]

  8. Spark-gap transmitter - Wikipedia

    en.wikipedia.org/wiki/Spark-gap_transmitter

    The invention of the radio transmitter resulted from the convergence of two lines of research. One was efforts by inventors to devise a system to transmit telegraph signals without wires. Experiments by a number of inventors had shown that electrical disturbances could be transmitted short distances through the air.

  9. Chirp spread spectrum - Wikipedia

    en.wikipedia.org/wiki/Chirp_spread_spectrum

    In digital communications, chirp spread spectrum (CSS) is a spread spectrum technique that uses wideband linear frequency modulated chirp pulses to encode information. [1] A chirp is a sinusoidal signal whose frequency increases or decreases over time (often with a polynomial expression for the relationship between time and frequency).