标签: radar

I’m fascinated with the history of technology. According to Wikipedia, Homo sapiens  emerged 500,000 years ago, and for half a million years pretty much nothing changed. Agriculture showed up 2% of those years ago; moveable type 0.1%, and electronics has been around for just 0.02% of the span of human existence. My late grandmother, who grew up in Manhattan, told me she knew someone “on the other side of the island” who had a phone. The first electronic computers appeared when my parents were in college. In engineering school none of us had calculators; we all used slide rules. But my kids were required to have a computer when they went off to school, and they have never lived in a household without at least several around. It’s rather wondrous how much things have changed.   But some things remain the same. Sailboats existed at least 7000 years ago  and today are still in use both recreationally and commercially. Here in Maryland skipjacks still dredge (the watermen pronounce it “drudge”) the Chesapeake Bay for oysters, and are only allowed to use an engine two days per week. In fact, engines aren’t allowed aboard a skipjack at all; they are in a dingy (called a “yawl boat”) which, on those two days, pushes the bigger boat. There is also still some shipping under sail, albeit somewhat whimsically, in the Caribbean, as well as in other locations around the world.   Recreational sailboats are an odd mix of the latest and ancient technologies. I thought readers might be interested in the use of electronics on such an ancient form of transportation, so here’s a tech tour of Voyager, my current hole in the water into which I throw money.   Voyager under sail in the Bahamas   Voyager is a 32’ fiberglass ketch, which means she has two masts. Built in 1977 she is considered small for a cruising sailboat, but as I get older I appreciate the small sails, anchors and other gear that seems to get heavier each year. As boats go she isn’t really loaded with tech; for instance, we don’t have a chart plotter, now considered essential equipment. I’ve been with friends who turn theirs on before leaving the slip and power along with their eyes glued to the screen, instead of watching the water, oncoming traffic, the birds, and the beautiful Bay. On Voyager we use paper charts. They are almost failure-proof, and there’s something special about leaning over the chart table, plotting your position, and thinking about other destinations. A chart becomes a worn friend. Coffee stains accumulate, blood sometimes, as well as myriad pencil lines showing today’s position as well as courses sailed in the past.   The technology of the sails and rigging has changed a lot in my sailing career. We used to use canvas sails and galvanized wire rigging. Masts (and the boat) were wood. Today the rigging is stainless steel, the sails dacron or nylon, the boat fiberglass and the masts aluminum. Deep-pocketed racers use exotics: carbon fiber masts, sails of Kevlar and other materials. We were looking at the rigging of a modern ocean racer and I had no idea what it was made of – some engineered material no doubt designed with little margin, as weight is everything in the go-fast world.   Electronics, of course, is where most of the change has happened. In the 70s my 1930s-era wood boat had a ham radio, an AM/FM receiver and a cassette deck. That was it. No marine radio. No depth sounder. Though it was possible to buy those, the price was not practical for those on a budget. A decade later, I had a 35 footer (also wood) and navigation was by still by sextant. I installed Loran C, but once more than two or three hundred miles from land it couldn’t get a signal. In 1991 a friend and I sailed her to England. GPS was available, but was fantastically expensive. We borrowed a hand-held unit from friends in the government. It burned through AAs so fast that it had to be off most of the time. Embedded systems were not as powerful then; it took 20 minutes to acquire and compute our position. If the sky was clear I’d race it and get a sextant position plotted before the GPS was finished.   The next year I entered the single-handed transatlantic race from England to Rhode Island. GPS prices had dropped to about $1000 and all of the racers bought units. That was too pricey for me, so I navigated with the sextant (though sank after 29 days at sea). One of the racers, a slight French woman, developed a minor problem with her engine which could have been fixed in minutes, but she didn’t know anything about diesel mechanics. We were allowed to use the engine only to charge the batteries. She also didn’t know how to navigate so, sans engine, elected to use her remaining charge to run the GPS, and hand-steered the final 1500 miles. That was quite a feat of which she was justifiably proud.    Voyager’s main GPS   Today Voyager has a GPS, of course, plus a spare hand-held unit. The main unit draws just 80 mA and is on all of the time. It cost a few hundred dollars and has been in service for 16 years.   And yet.   An old maxim is to never trust a single navigational aid. I generally do at least some sextant navigation at sea, to keep in practice and as a check on the electronics. On one trip to Bermuda we left the GPS off just for fun. Five miles out with the island clearly in sight we turned it back on. The position it gave was off by 20 miles. Turns out the Navy was conducting some experiment that confused navigators island-wide.    My sextant, purchased 40+ years ago. It is on a book of tables used in reducing the sight.   With a sextant one measures the angle between the horizon and a star, planet, moon or sun. You’ll only get that particular angle if you are on a circle a certain distance from where that body is directly overhead on Earth. Walk closer to the body, and the angle increases. Walk away, it decreases. Observe two objects, or the same object at different times (adding in corrections for the boat’s motion) and you are at one of the intersections of the two circles. Accuracy is important; an error of one minute of arc throws your position off by a mile. Since the observation is taken from a small boat in sometimes heavy seas that accuracy can be hard to obtain.   The sextant angle has to be reduced via some simple math and then plotted. The sailor typically does this several times a day, which would make a deep sea chart, which spans thousands of miles, obliterated with plots, so we draw on “universal plotting sheets,” and transfer the noon position once per day to the big chart. Calculators are sold that will do all of this, but somehow using a sextant plus a billion transistors seems an odd mix of technologies, so I prefer to work them out by hand.   A universal plotting sheet with a few days of positions plotted. The math are steps in reducing the sights.   Just about everyone has a marine VHF radio today. They’ve gotten cheap, waterproof, and are filled with functionality. Ours shows barometric readings for no discernable reason. The boat’s main barometer is much more accurate.   Voyager has a small network where the GPS sends position information to other instruments, including the VHF. That has an “Emergency” button that broadcasts a digital HELP which includes our position and a unique number assigned to the boat. It’s also possible to dial in any other vessel’s unique ID, if you know it, which will set off an alarm on their bridge, telling them to take the call. It’s line-of-sight with a range of around 30 or 40 miles.   We also have a waterproof hand-held VHF which is handy when going through bridges, for example on the Intra-Coastal Waterway. While steering it’s easy to use the hand-held to request a bridge opening.   VHF Radio   Ham radio was one of the gateway drugs for me into electronics. Today, the only time I’m on the air is when sailing offshore. We use a ham SSB radio to get phone patches home – hams ashore connect us into the phone system. There are also various weather and informational networks on the air. On long trips we often sail in company with a friend’s boat, but his is faster and he’ll pull hundreds of miles ahead. Every morning and evening we chat and exchange positions for safety and community. On one weeklong trip we each had a son aboard and they played Battleship in the evenings over the SSB.   The SSB can output up to 100 watts into the antenna. Since it tunes from 500 KHz to 30 MHz getting an impedance match is tough. We have a manual tuner with SWR meter to match the radio to the antenna, but this was a poor purchase. I’m the only one in the family who understands it so no one else can tune the radio. One of these days that will be replaced with an automatic tuner.    Yaesu ham radio Antenna Tuner   We do have RADAR but don’t use it a lot. The set takes 4 amps. Were we to run it all the time that’s 100 amp-hours/day which is just about our entire energy budget. The fridge needs 50 Ahr, and I am more interested in cold beer than RADAR. It’s on when a situation demands it, like a difficult landfall at night or when working in fog.   The RADAR uses network data to show the latitude and longitude of any echo selected by a cursor. That’s useful for navigation, and for hailing ships on the VHF. Instead of calling “ship whose lights I see,” we can call “ship at xxx lat and yyy lon.”   They usually don’t answer.   RADAR showing docks in the marina.   One of the best innovations in decades for vessels plying the seas is the Automatic Identification System (AIS). All vessels over 300 gross tons are required to have an AIS transmitter, which broadcasts a lot of information a few times a minute (depending on speed). Position, speed, course, vessel name, that unique ID number, and a lot of other info squirts out over a reserved VHF frequency. We have an AIS receiver that has a RADAR-like display. It, too, listens to the GPS and shows us at the center of the screen. All targets within a selectable range are shown. You can set a guard zone; if a vessel comes within the zone an alarm goes off.   We generally sail very short-handed, just my wife and myself. When you’re at sea, sailing 24/7 for weeks, watch keeping can be a problem. We do sleep at night; I get up every hour or so and look around, but the AIS is always on guard, ready to wake us should a ship get near. Ships usually answer a call when we ring their alarm using their unique ID that the AIS displays. Sometimes a bored second officer will chat for a while as we pass, but usually the calls are very businesslike as we discuss collision avoidance.   I’ve thought about buying an AIS transmitter and programming it to identify us as a 1000 foot-long aircraft carrier. That would certainly keep others away.     The AIS   There’s one critical piece of gear I hope to never use. It’s the EPIRB, the Emergency Position Indicating Radio Beacon. Waterproof, it floats, and when activated sends out a HELP message to orbiting spacecraft on 406 MHz. It lives in our ditch kit. If the boat were sinking we’d deploy the liferaft, a sort of Swiss-army boat that inflates automatically, and grab the ditch kit. Each EPIRB has a unique number so the Coast Guard knows who is signaling. If they pick up a broadcast they call contacts we’ve registered to insure that it wasn’t an accidental message. Otherwise they’ll contact ships in the area to arrange for a rescue. In the ’92 singlehanded transatlantic race I did activate an EPIRB; though 500 miles from land, within four hours a Canadian Navy P3 Orion was overhead and calling on the VHF.     EPIRB   There’s more, of course. Electronics pervades our lives. A depth sounder, knotmeter, anemometer, wind direction indicator and more grace little Voyager. All of this stuff is considered essential today, yet just a couple of decades ago most was either unavailable at any price, or was too expensive for most sailors. No doubt in a decade or two this gear will be obsolete and some new marvels will be considered essential.

Recently, I finished reading Richard J. Aldrich's GCHQ: The uncensored story of Britain's most sensitive intelligence agency . The Government Communication Headquarters (GCHQ), Britain's equivalent of the NSA, is a direct descendant of Bletchley Park, where the British decoded German messages encoded by the Enigma machine and where the world's first programmable electronic digital computer, the Colossus, was built. It was the stomping ground of Alan Turing during the Second World War and -- according to Winston Churchill -- where the war was won. In my not-so-humble opinion, the greatest technical museum for any electrical engineer is Bletchley Park.   Back to the book, which is about how the British monitor telecommunications traffic from around the world and decode it to provide "intelligence" for military and political purposes. It is a fairly weighty tome, long on facts and short on anecdotes. It is also not a particularly easy read. However, on page 400, I was wading through the description of the Falklands War when I came across this sentence: "The Argentinean Air Force's traffic was the hardest to read, since it had recently invested in new encrypted communications made by a subsidiary of the British defence company Racal, based in South Africa."   "Just a minute," I said aloud to myself, "that was one of mine." Actually, this is a bit of an exaggeration. In fact, I had designed the first prototype -- the proof of concept -- for the microprocessor that controlled the digital tuning of a radio to operate as a frequency-hopping device. It was a very early application of a microprocessor. It synchronized the transmission and then controlled the calculation of the next frequency to which the transmission would hop.   The facts presented in the book are a little suspect, since by that time Racal had sold the organization to a South African company, Grinaker Electronics, but perhaps Racal still held some shares or was responsible for international marketing. The book makes the point that, when it comes to arms supplies, there are some very strange bedfellows, so the fact that this system had ended up in Argentina did not surprise me too much. What did surprise me was that this system should come back into my life 38 years later. It felt really surreal, almost like I was looking at the back of my own head. Maybe I have been around long enough to be on my second lap now.   All this reminded me of the British engineer Sir Robert Alexander Watson-Watt, was a significant contributor to the development of radar during the Second World War. He emigrated to Canada in the 1950s and -- later in life -- was caught in a radar speed trap in Ontario. He is reported to have said to the police officer, "Had I known what you were going to do with it, I would never have invented it." He even wrote a poem about it:   Pity Sir Robert Watson-Watt, strange target of this radar plot And thus, with others I can mention, the victim of his own invention. His magical all-seeing eye enabled cloud-bound planes to fly but now by some ironic twist it spots the speeding motorist and bites, no doubt with legal wit, the hand that once created it.   Does any of this strike a chord with you? Have you ever been blindsided by your own design? If so, it would be great if you would share your experiences in the comments below.   Aubrey Kagan Engineering Manager Emphatec

I recently read Richard J. Aldrich's GCHQ: The uncensored story of Britain's most sensitive intelligence agency . The Government Communication Headquarters (GCHQ), Britain's equivalent of the NSA, is a direct descendant of Bletchley Park, where the British decoded German messages encoded by the Enigma machine and where the world's first programmable electronic digital computer, the Colossus, was built. It was the stomping ground of Alan Turing during the Second World War and -- according to Winston Churchill -- where the war was won. In my not-so-humble opinion, the greatest technical museum for any electrical engineer is Bletchley Park.   Back to the book, which is about how the British monitor telecommunications traffic from around the world and decode it to provide "intelligence" for military and political purposes. It is a fairly weighty tome, long on facts and short on anecdotes. It is also not a particularly easy read. However, on page 400, I was wading through the description of the Falklands War when I came across this sentence: "The Argentinean Air Force's traffic was the hardest to read, since it had recently invested in new encrypted communications made by a subsidiary of the British defence company Racal, based in South Africa."   "Just a minute," I said aloud to myself, "that was one of mine." Actually, this is a bit of an exaggeration. In fact, I had designed the first prototype -- the proof of concept -- for the microprocessor that controlled the digital tuning of a radio to operate as a frequency-hopping device. It was a very early application of a microprocessor. It synchronized the transmission and then controlled the calculation of the next frequency to which the transmission would hop.   The facts presented in the book are a little suspect, since by that time Racal had sold the organization to a South African company, Grinaker Electronics, but perhaps Racal still held some shares or was responsible for international marketing. The book makes the point that, when it comes to arms supplies, there are some very strange bedfellows, so the fact that this system had ended up in Argentina did not surprise me too much. What did surprise me was that this system should come back into my life 38 years later. It felt really surreal, almost like I was looking at the back of my own head. Maybe I have been around long enough to be on my second lap now.   All this reminded me of the British engineer Sir Robert Alexander Watson-Watt, was a significant contributor to the development of radar during the Second World War. He emigrated to Canada in the 1950s and -- later in life -- was caught in a radar speed trap in Ontario. He is reported to have said to the police officer, "Had I known what you were going to do with it, I would never have invented it." He even wrote a poem about it:   Pity Sir Robert Watson-Watt, strange target of this radar plot And thus, with others I can mention, the victim of his own invention. His magical all-seeing eye enabled cloud-bound planes to fly but now by some ironic twist it spots the speeding motorist and bites, no doubt with legal wit, the hand that once created it.   Does any of this strike a chord with you? Have you ever been blindsided by your own design? If so, it would be great if you would share your experiences in the comments below.   Aubrey Kagan Engineering Manager Emphatec

In 1992 I participated in OSTAR. It is a single-handed sailboat race from the UK to Newport, Rhode Island organized every four years by the Royal Western Yacht Club of Plymouth, England. At that year, I went with my then 30-year-old wooden 35-footer. And two decades ago this week I abandoned that vessel, climbing onto a German container ship 350 miles from Newport after 29 days alone at sea ( See photo below ). But where, exactly, was Amber II on July 8 of that year? It's hard to say. The previous year a friend and I sailed her to Newfoundland and thence to Plymouth. At the time GPS was hideously expensive. No one really knew where anything was. Bermuda was reported to be three miles SW of its charted position. Newfoundland's sailing directions warned that the island might be as much as 10 miles away from the location plotted on the chart. We had borrowed a GPS, one with military precision (pre-Clinton commercial GPSes had downgraded accuracy) from special friends in the government, but it took 20 minutes to compute a position. We didn't have enough AAs on board to run the thing very often, so navigated by sextant with only the occasional GPS fix. Amber II, just below the ship, poses for the P3 Orion 1992 saw the collapse of the price of GPS – for $1000 ($1600 today) one could buy a unit which would report positions accurate to a couple of hundred meters. In the week prior to the race all but one of the 67 skippers bought a GPS in Plymouth via a special deal offered to the racers. My finances were at the breaking point, and a GPS was out of the question. Celestial navigation has been used for centuries to determine position. The idea is simple: measure the angle between the sun (or star, planet or moon) and the horizon, and, if you know the time it's possible to calculate where you are. Think of it this way: At any given instant the heavenly object is directly above one location on Earth. That means the angle you measure puts you on a circle some distance from the object's ground position. Observe two bodies and your location is at the circles' intersection. ( The circles generally intersect at two points thousands of miles apart; one presumably at least knows what ocean you're in ). The reality is a bit grittier. An observation error of one minute of arc ( one sixtieth of a degree ) induces an error of a mile. Yet at 50 degrees north the ocean is always rough, so the navigator is being tossed about violently while getting soaked in cold spray. It's impossible to sight two objects at the same time, so corrections are needed. Get the time wrong by four seconds and another mile of error creeps in. The sextant has errors, as does the clock, and the bodies in the sky don't move in quite the way predicted by the ephemeris tables, so correction after correction has to be applied, and the results carefully plotted carefully despite heavy seas. Or, today, one merely looks at the screen and records GPS coordinates accurate to a handful of feet. In a single generation the entire history of navigation has been tossed overboard, replaced by cheap electronics with unprecedented accuracy. In 1992 the Canadian P3 Orion located Amber II by homing in on my distress beacon. They found a ship but could not supply them an accurate vector to Amber II as their navigational tools weren't much better than mine. Today, one wouldn't bother to read off all of the digits of latitude and longitude from the electronic box as the precision far outstrips that required. ( In fact, most GPS users are clueless about the units' precision. An app on my iPhone displays coordinates to one-thousandth of a second of arc, which is about an inch, far exceeding the GPS's capabilities. ) The microprocessor has displaced all of traditional navigation techniques. Many sailors today barely know how to read a chart. One acquaintance navigated from below as his boat approached Virgin Gorda, reading data off the instruments. The crew on deck warned about the rocks clearly visible ahead, but they weren't shown on his display. They hit the rocks. Voyager, my current boat, is a 32 foot ketch, which is quite small for ocean sailing. But in that tiny envelope we carry three GPSes. And RADAR. Then there's the AIS which has a RADAR-like screen that displays the position of all ships within 30 miles, using data packets they all transmitted several times a minute on VHF frequencies. The RADAR detector alarms when it picks up a signal. A network connects the GPS to the AIS, the RADAR and the marine radio. A panic button will cause the radio to broadcast the boat's unique identification code and position to any nearby vessel. It's possible to add the autopilot to the network so it will automatically change course as needed, but that seems a silly feature to me. Voyager is not a high-tech boat and does not even have a chart plotter, but she fairly bristles with electronics that sense ocean temperatures, ship positions and much more. None cost much and all are astonishingly reliable. And all are made possible by microprocessors. But we also still carry my sextant, which I clutched while scrambling up the ship's cargo net. Today that Tamaya would cost around $2000, ten times what I paid for it 40 years ago, and the price of about twenty GPSes. It's not particularly accurate, by today's standards, but tradition still has value. So every year I take some sights to stay in practice. There's a certain satisfaction in repairing a diesel engine, fixing the rigging, and figuring position without the aid of millions of transistors. But yesterday, at a West Marine store, my wife lovingly eyed a 12" full-color touch screen chart plotter. I told her we just don't have room for the thing. She suggested making room by getting rid of the sextant.