Background Data Military Communication and The Radio Game Randy H Katz CS Division EECS Dept University of California Berkeley Spring 2010 Quick History Electricity and Magnetism in the 19th Century Alessandro Volta 1745 1827 Volt the unit of electrical potential electromotive force Metals are movers of electricity arrange metals in an electromotive series based on ability to gain or lose positive charges by contact Voltaic pile dissimilar metals separated by membranes moistened by acid the electric battery E M History Andre Marie Ampere 1775 1836 Amp unit of electrical current velocity of electrical flow Demoed that magnetic effects between two current carrying wires are the same as those between a wire and magnet Electrodynamics mechanical forces between current carrying conductors critical for the design of telegraph apparatus telephone receivers and loud speakers E M History Georg Simon Ohm 1789 1854 Ohm the unit of electrical resistance Ohm s Law I V R fundamental relationship between voltage aka electromotive force current and resistance E M History Hans Christian Oersted 1777 1851 Forces of nature light electricity magnetism gravity variations on one source Magnetic field exists around a current carrying conductor A deflecting force such as magnetism was something completely new Connection between electricity and magnetism Demonstrated this effect with the deflection of a magnetic compass needle E M History Michael Faraday 1791 1867 Farad electrical unit of capacitance stored electrical charge Built on Oersted Demoed electric motor wire carrying current rotated around a fixed electromagnet Wire rotates around magnet Also showed how to make magnet rotate around wire Electrical Telegraph Telegraph Writing at a distance Built on work of Volta Faraday Oersted Signaling by means of electrical current along a conducting wire Basic idea deflect a needle by connecting and disconnecting a battery to a wire By alternating the connection between the and poles of the battery the deflection could be enhanced needle reverses its swing Wheatstone and Cooke 5 magnetic needles deflected in pairs selecting one of 20 letters of the alphabet Original system required 5 wires Later reduced to 2 by using coding techniques 20 km of line installed along railway routes in 1838 Grows to 4000 miles by 1852 Samuel F B Morse 1835 printing telegraph key switches on current to electromagnet Pencil makes mark as long as key is held down drawing a long or short line on a moving strip of paper 1837 Morse code dots and dashes encode alphabet based on frequency of occurrence in English text James Clerk Maxwell 1831 1879 Maxwell s equations described fundamental relationship between electricity magnetism wave propagation Underlies all radio and cable communications Light and radio waves are the same phenomena Provides theoretical explanation for why radio waves can be focused and reflected just like light Electromagnetic Radiation Electromagnetic Radiation Heinrich Hertz 1857 1894 Hertz unit of frequency cycles per second Demoed experimentally wave character of electrical transmission in space Developed apparatus that could transmit high frequency meter length waves Radio Communications 1895 Guglielmo Marconi demoed electromagnetic radiation created by spark gap could be detected long distance Main Cable Lines 1911 Radio Communications in WWI Wireless plays key role Within hours of hostilities British Navy cut Germany s overseas telegraphic cables systematically attack German overseas radio stations and shut them down Germans similarly cut Britain s overland cables Marconi completes several radio stations under contract from the British government to reestablish comms with overseas possessions Techniques of communications intelligence comint message interception cryptoanalysis direction finding jamming and intelligence gathering developed rapidly Airborne Radio Communications in WW I It became clear as we made our preparations was not going to be anywhere near as simple as it had sounded The first problem was the shear weight of the wireless apparatus The guts of the system was a marvelously archaic contraption called a sparkgenerator This worked by creating an arch through the teeth of a brass cog wheel spinning against an electrode Every time a tooth passed the electrode a spark jumped across the gap and in this way when connected to the aerial it would produce a hideous rasping crackle barbed wire made audible The principle of signaling was that the operator worked a Morse key to turn this excruciating noise into a signal a crackle for a dash and a short one for a dot Airborne Radio Communications in WW I That part of the wireless alone weighed about thirty kilograms But there were all the other accoutrements that went with it Power was provided by a dynamo fixed on to a bracket under the aeroplane s nose and driven by a leather belt from a pulley wheel on the propeller shaft that weighed about seven kilograms Then there was the aerial twenty meters of wire with a lead weight at one end to trail behind us in flight plus a cable reel to wind it in when not in use about ten kilograms worth in all Other accessories comprised a signal amplifier a tuning coil an emergency battery an ammeter a set of signal rockets plus pistol and a repair kit Altogether the wireless apparatus weighed about 110 kilograms Or to put it another way the weight of a very fat man as a third crew member Portable Radio circa WW I Radio Communications WW II Command and control in lightening warfare blitzkrieg Mechanized warfare demands leading from the front radios in tanks let to quantitative edge Rapid pace of operations does not allow for laying of wires by pass hard points to infiltrate behind the enemy Combined arms coordination Bring to bear infantry tanks artillery air power even naval power Man pack radios Planes and ships don t have wires A Bridge Too Far A Bridge Too Far A Bridge Too Far Insurgency Study See Class Web Page http www cs berkeley edu randy Courses CS39K S10 insurgentessayreq html Due 10 March 2010 The Radio Game Two teams Blue and Gold Objective be first team to collect the complete set of message segments and return with them to 310 Soda Hall Messages spread around Soda Hall and adjacent buildings You must retrieve them in the correct order Report to me your current message segment and I will provide you with the location of the next segment The Radio Game I tell you where the next message segment is located You