Although Guglielmo Marconi was the first to put the theory of radio waves into practice, the groundwork for his feat was laid in the 19th century by James Clerk Maxwell, Heinrich Hertz, and Nikola Tesla. Maxwell theorized and Hertz confirmed the feasibility of transmitting electromagnetic signals.
VLF Transmission The transition from the international Morse code keying transmission system to the automatic teleprinter system came about much later on the very-low-frequency circuits than on those in the high-frequency band, This was primarily due to the extremely low bandwidth characteristic of the huge shore station antennas at the very-low frequencies, which imposed a limit on the speed of transmission 20 words per minute, continuous wave, international Morse code keying to about one-half that required for teleprinter operation at its lowest speed.
In overcoming this limitation, NRL devised the first teleprinter system providing effective operation on the very-low-frequencies This system was self synchronizing and provided the encoding of a standard teleprinter signal into a four level signal having one half the keying rate of the original, The transmitter was shifted through the four frequency levels by the encoded signal which, as modified, could then be accommodated by the bandwidth of the antenna, At the receiver, a decoding device converted the received four level signal back into its original form for operation of the teleprinter.
A novel, stable, regenerative circuit provided a much higher degree of selectivity in the frequency-shift receiver than had previously been attained 25 Hz bandwidthA specially designed discriminator permitted segregation of the signals on the four frequency levels, which were separated by a very small difference in frequency 4 Hz.
In responding to this situation, NRL developed a VLF facsimile transmission system which was first to provide reliable command and control communication from a single high power transmitting station in the United States to continuously submerged submarines when operating in any critical world area The system was installed on all Polaris submarines and provided highly reliable command-control communications during the critical period that followed, This system became known as "Bedrock".
The frequency-shift receiver utilized the novel techniques for high selectivity and discrimination previously devised for the VLF teleprinter system, Transmitter components were provided for installation at shore stations: In the trials of the system made with this submarine in the Mediterranean Sea area, excellent submerged reception results were obtained on transmissions from the station at Annapolis, Maryland.
The system utilized two frequency levels for keying with provision to avoid the large voltage and current transients previously experienced when the large quantity of oscillatory energy in the antenna system was abruptly changed in frequency.
These transients had, at times, caused a flashover of "horn-gaps" and other protective devices followed by objectionable shutdown of transmitters due to overload. In certain instances, critical damage occurred, such as the burnout of antenna loading inductance cable, rendering the station inoperative for a considerable period.
The transients were avoided by beginning each successive "mark" and "space" frequency shirt at the zero-crossing points of the "mark" and "space" frequencies, when these points were coincident in phase, and arranging the rate of change of frequency to be linear during the transition process.
The transition period was of such length as to hold the sideband energy generated during transition within the frequency bandwidth of the antenna, Maximum utilization of the antenna bandwidth was obtained by very precisely maintaining the "mark" and "space" frequencies; this was possible with NRL-devised techniques.
Full utilization of the antenna bandwidth and confinement of the sideband energy to within its limits are major factors in maximizing the rate of transmission, The system permitted changes in the transmitter frequency to be made quickly and easily.WYNG [Evansville IN] Now: Eric says (4/08), "I'm traveling the country, working as a commercial artist with several large home builders; I'm also looking for another opportunity to continue my radio career.".
A Brief History of Radio*. Though the discovery of electricity and the beginnings of radio can be traced back to Thales of Miletus (static electricity charge via amber,) the first deliberately sent electromagnetic "signal" was the result of experiments performed in by a Virginia dentist named Malon Loomis.
Equipment Nomenclature - good Electric Radio article by Ray Mote Shipboard Electronic Equipments: NAVPERS NAVPERS A NAVPERS B NAVPERS C: *** , *.
Telephone tapping (also wire tapping or wiretapping in American English) is the monitoring of telephone and Internet conversations by a third party, often by covert means. The wire tap received its name because, historically, the monitoring connection was an actual electrical tap on the telephone line.
Excerpt from "Evolution of Naval Radio-Electronics and Contributions of the Naval Research Laboratory" - Louis A, Gebhard, GPO VLF Transmission. In any case, it all started with the discovery of radio waves—electromagnetic waves that have the capacity to transmit music, speech, pictures, and other data invisibly through the air.
Many devices work by using electromagnetic waves, including radios, microwaves, cordless phones, remote controlled toys, televisions, and more.