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`Radar and LORAN
`July 1959 Popular Electronics
`
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`Mostly just old farts like me remember anything about LORAN (LOng RAnge
`Navigation). My familiarity with it came not from boat navigation, but from
`airplane navigation. Before LORAN became totally obsolete due to GPS (phased
`out in U.S. and Canada in 2010), the transmitter stations were commonly
`tuned in in order to obtain positional fixes via triangulation . Whilst taking flying
`lessons at Lee Airgort, in Edgewater, Maryland, the ground instructor included
`it in the lessons, and even the FAA Private Pilot exams had a question or two
`on LORAN. The el cheapo Piper Colts that I flew were lucky to have a YQB
`(VHF omnidirectional range ) receiver in it, so I never actually used LORAN.
`They did have direction finders (DF), which could tune in, among other things,
`VHF television station channels to get a bearing (but not distance) to the
`stations. This article touches on the principles of both radar (radio detection
`and ranging) and LORAN .
`BTW, why do we still capital ize all of the acronym "LORAN" but not "RADAR?" Variations of LORAN, like Loran-C, are
`not fully capitalized . Just wondering ...
`
`July 1959 Popular Electronics
`Table of Contents
`UEWioNICS " Wax nostalgic about
`and learn from the
`,,,=-- history of early
`electronics. See
`articles from f!Ql2J.!.@L
`Electronics, published
`October 1954 - April 1985. All
`copyrights are hereby
`acknowledged.
`
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`For more than a decade, the navigator has had electronic eyes
`which penetrate fog and darkness, seek out hidden dangers, and
`chart the surroundings for him. Radar (Radio Detection and
`Ranging) was a secret word during the early part of World War II
`and has been credited by many as having been most instrumental in
`bringing victory to the Allies in Europe and the Pacific. Loran (Long
`Range Navigation) was also developed during World War II as a
`rapid and simple way of getting accurate navigational fixes. Today
`more and more standard navigational charts have loran lines,
`making it possible to transform a loran receiver reading directly into
`a graphic navigational fix.
`RADAR
`A crude form of "radar" was in use before electronic radar came into
`being. From the beginning of time, navigators have used audio
`signals to determine their distance off steep shores hidden in fog ,
`by sounding a short blast with a whistle or horn and then listening
`for the echo. Knowing the speed of sound to be approximately 1100
`feet per second, if it took five seconds for an echo to return , the
`shore or cliff was known to be about a mile away.
`A radar unit transmits short bursts of microwave radio energy (between 1000 and 30,000 megacycles) which are
`reflected by solid objects. Distance is determined by the length of time it takes a radar pulse to hit a target and return .
`Since radio waves travel at the speed of light - 186,000 miles per second-the time from the instant a radar pulse is
`transmitted to the instant the echo returns is' measured in microseconds (millionths of a second).
`In a typical radar unit, more than a thousand pulses per second are transmitted in rapid succession as if fired from a
`machine gun . The pulses are spaced far enough apart in time to allow an echo to return before the next pulse is
`transmitted . The time required for a pulse to travel to a target and return as an echo is measured on a cathode-ray
`tube, similar in many respects to a TV picture tube. The echoes appear on the round screen as glowing "blips."
`Antenna Requirements. Radar pulses should travel in a narrow beam in order to allow the detection of small objects
`and the determination of direction as well as distance. A modified form of parabolic reflector, the so-called "dish"
`antenna, is used to focus microwave signals into a narrow beam. The antenna is rotated 3600 horizontally so it can
`scan in all directions, and the antenna rotator motor is synchronized with another motor at the radar screen .
`As the antenna rotates, the trace line on the radar screen sweeps around with it. This is done by rotating the magnetic
`sweep coils around the neck of the cathode-ray tube. The sweep starts at the center of the round tube face and
`rotates in step with the antenna. It looks something like a windshield wiper. Blips appear along the trace whenever a
`radar echo is received .
`A long-persistence picture tube is used, so that the echoes remain on the screen until the sweep has rotated a full
`revolution and sometimes longer. As the radar beam rotates, a map of the surrounding area is "painted" on the
`screen. Large areas, such as the shoreline and islands, appear as large lighted masses. Boats and other small objects
`appear as small blips. Lighter hash or clutter may appear near the center of "home" point on the screen due to "sea
`return," a mass of echoes from the surface of the water.
`Although marine radar equipment some-times has a range up to 40 miles, maximum range is limited by the height of
`the antenna above water. Radar is a line-of-sight device, and as the antenna height is decreased, the effective range is
`reduced . While it might be interesting to see objects 20 miles away, objects within a range of eight miles are generally
`of more concern to the navigator.
`
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`About RF Cafe
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`Exhibit 1021
`IPR2022-00426
`Page 1 of 2
`
`

`

`Copyright: 1996 - 2024
`Webmaster:
`Kirt Blattenberggr,
`BSEE - KB3UON
`RF Cafe began life in 1996
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`Typical Installation. A marine radar installation consists of a
`transmitter, receiver, antenna, monitor, and power supply. One
`antenna serves both transmitter and receiver since the
`transmitter is turned on for only a microsecond or so and then
`pauses to allow the receiver to intercept the echo. The antenna is
`automatically switched from the transmitter to the receiver
`electronically.
`Use of radar on pleasure craft is limited by space, the capacity of
`the electric power source, and the owner's pocketbook. Prices for
`radar units start at about $1500. Power requirements are heavy,
`running from 300 watts to more than 1500 watts, which means
`that small boats equipped with 12- volt batteries may not have
`enough reserve electrical power for radar equipment. An auxiliary
`generator driven by a small engine can be used if a boat does not
`have 32- or 115-volt batteries.
`An FCC radio station license is required and the radar equipment
`must qualify for FCC type acceptance. It must be installed and
`serviced under the supervision of a person holding a suitable FCC
`operator's license endorsed for radar. The master of a vessel,
`however, may use a licensed radar set without being required to
`have an operator's license. No one else may use the radar except
`under his personal supervision.
`LORAN
`Conventional navigational devices such as radio direction finders
`are being supplemented on military and commercial vessels by
`loran, with its longer range than a conventional radio direction
`finder, no loop to rotate, and greater accuracy. Like radar, loran
`employs pulses, but operates at much lower frequencies (1750-
`1950 kc.). Loran, however, does not require a transmitter on
`board ship.
`Sometimes called an "electronic stop watch," loran measures the
`difference in the time required for radio signals to arrive from
`different synchronized radio stations. Since radio waves travel at
`constant velocity, the traveling time of a signal is proportional to
`the distance between transmitter and receiver.
`Chain of Operation . A loran chain consists of two or three radio
`stations, a "master" and one or two "slaves. 11 These transmitters
`are located from 200 and 400 miles apart and transmit short
`pulses simultaneously or offset by a precise time interval. The
`pulses are repeated between 25 and 35 times per second.
`The difference in arrival time of signals from a group of loran
`stations is measured by a loran unit aboard ship. To get a "fix," it
`is necessary to take readings on two pairs of loran stations or a
`single three-station loran chain. The ship is located at the point
`where the hyperbolic curves or distance lines on the loran chart
`intersect.
`Daytime range of loran is around 700 miles over water and about
`450 miles at night, using the direct ground wave from the loran
`stations. At night, the reflected sky wave permits use at distances
`up to 1400 miles, but the results are less accurate. Error in line
`position of up to ±3 nautical miles and in fixing of up to ± 10
`nautical miles is apt to occur in using night sky waves at extreme
`distances.
`Power requirements for loran are more modest than for radar (as
`little as 135 watts), but the cost of the equipment is about the
`same, starting at around $1500. For reliable fixes in all kinds of
`weather, loran is of great importance to the boat-man who
`ventures offshore beyond the range of radar or direction finders.
`
`Posted July 9,
`
`Ceiling radar installation saves space and allows
`shorter lead-in cables to antenna atop
`wheelhouse, (RCA photo)
`
`Lightweight. low-cost radar equipment can be
`installed on a 28-footer without placing too much
`of a burden on the ship's battery. (Bendix-Pacific
`photo)
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`Loran equipment, excellent for long range
`navigation. (Edo Corp. photo)
`
`(original 10/ 2/2011)
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`Exhibit 1021
`IPR2022-00426
`Page 2 of 2
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