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Carry your compass
On Mon, 05 Jan 2009 18:39:51 -0500, Tom Francis - SWSports
wrote: We did that too. As a large geographic area that is almost completely rural in nature, it was very important as some driveways can be a 1/4 mile long. The drive is only a hundred feet, but there are trees and a massive hedge. My place needs at the street numbers, the next door neighbor doesn't. Casady |
Carry your compass
On Tue, 06 Jan 2009 00:34:07 GMT, (Richard
Casady) wrote: On Mon, 05 Jan 2009 17:01:19 -0500, Tom Francis - SWSports wrote: On Mon, 05 Jan 2009 18:04:26 GMT, (Richard Casady) wrote: On Mon, 05 Jan 2009 09:40:21 -0500, Dave Brown wrote: Does anyone have any experience with working the GPS from the centre of a moving vehicle? Does it need to be near glass to receive signals? Metal blocks all radio. As a strict statement, that is true, however radio signals can bend around objects (demonstrated by radar's ability to see behind objects). As such a car presents the opportunity to receive signals inside by virtue of the physics of radio wave propogation and the ability to move along the surface of metal. The only way to completely restrict the reception of radio signals is to build a grounded solid metal box of some sort or use a grounded fine wire mesh in which the gaps are less than 1/100th of the base line wavelength. That is true enough, but you generally need to have a view of the sky unblocked by solid metal. The closer to the glass, the more signal you get. No problem in an open boat, or inside a fiberglass pilot house. Now tell how me the cell phone worked inside a steel ship a thousand miles from land. Magic, obviously. Nothing on the bill from either the ship or the phoneco, so it must have been magic. Repeaters. Scientific Atlanta builds them into the TV cable systems onboard cruise ships. Same for two way radio systems in hospitals, industrial plants and maintenance for large office buildings. Being digital it's pretty simple to do - spread spectrum receivers and digital routers out to the transmitter. I would assume that the cost is built into the price of your cruise ticket. Or if you prefer, FM. As in F*ckin' Magic. :) I saw the coolest thing the other day in the new town ambulance. They can take a cardiogram and transmit it direct to the ER via secure encrypted radio link giving real time data for evaluation. The attending can order drug intervention at that time to the Paramedic. Everything is recorded on mini-disc - blood O2, saturation, BP - really neat stuff. My understanding is that even defib can be controlled from the hospital if there isn't a Paramedic onboard. Kewl. Bay State's Hospital Pedi unit has a new ambulance that is completely state of the art for patient transfer - monitors everything enroute in real time back to the hospital with an attending on immediate call if something goes south - like a neo-natal transfer. Far cry from the old days when it was a wing and a prayer and all analog communications. Neat stuff. |
Carry your compass
On Mon, 05 Jan 2009 20:58:15 -0500, D K
wrote: In a 25hp rowboat? When is the last time you were out of sight from shore, dummy? Ahem - it's not a rowboat. -- "Every normal man must be tempted at times to spit on his hands, hoist the black flag, and begin to slit throats." H. L. Mencken |
Carry your compass
On Mon, 05 Jan 2009 18:18:34 -0600, Vic Smith
wrote: On Mon, 05 Jan 2009 17:01:19 -0500, Tom Francis - SWSports wrote: The only way to completely restrict the reception of radio signals is to build a grounded solid metal box of some sort or use a grounded fine wire mesh in which the gaps are less than 1/100th of the base line wavelength. Tin-foil hats don't work? http://www.stopabductions.com/ Oh wait, that's "different" waves. http://www.lessemf.com/personal.html I thought Maxwell Smart had this stuff figured out with the cone of silence. http://www.osha.gov/SLTC/radiofreque...theffects.html -- "Far better it is to dare mighty things, to win glorious triumphs even though checkered by failure, than to rank with those poor spirits who neither enjoy nor suffer much because they live in the gray twilight that knows neither victory nor defeat." Theodore Roosevelt |
Carry your compass
On Mon, 05 Jan 2009 21:14:15 -0500, wrote:
I was always curious why cell phones etc work so well in airplanes, even at altitude. My wife was surfing on her Blackberry all the way to Pennsylvania. Same deal. -- "An idealist is one who, on noticing that a rose smells better than a cabbage, concludes that it will also make better soup." H.L. Mencken |
Carry your compass
"Tom Francis - SWSports" wrote in message ... On Mon, 05 Jan 2009 09:40:21 -0500, Dave Brown wrote: Does anyone have any experience with working the GPS from the centre of a moving vehicle? Does it need to be near glass to receive signals? As a general rule, yes. You can receive signals away from windows depending on where the constellation is at any one given time, but that can be a hit or miss situation. If it's located near the floor, probably not. If it was sitting on your lap though, it will work, but not with the same accuracy - it all depends on the location of the constellation at the time, where the GPS is located, etc. There are situations where even situated near glass it will struggle with finding satellites - something about how the glass is coated or the composition of the substrate film used to make safety glass. Some RFI devices (like Easy Pass transponders) don't work on certian cars for that reason. I can receive GPS signal in the middle of my house - then again, I'm located fairly high and it's a one story ranch. Problem is the very low power of the signals. I can receive the signals in the one story part of the house, but not the front 2 story part. Son in law works on the GPS sats and they are looking at new system in 10 years or so. But that is good as good job security for SIL. As to shielding rooms, other son in law is a contractor building MRI rooms. A contruction segment that is still going strong. Special leaded windows as well as very expensive screening in the wall. |
Carry your compass
"Tom Francis - SWSports" wrote in message ... On Mon, 05 Jan 2009 13:47:13 -0500, wrote: On Mon, 05 Jan 2009 06:12:16 -0500, Tom Francis - SWSports wrote: I've heard that before and I find it an interesting comment. We have some fairly dense woods around my house - 100 plus acres of woods in fact mostly swamp oak, pine, hemlock, birch and sugar/swamp/rock maple. Most trees are in the 40/45 foot category and in the summer there is a dense canopy. Back when I was still an active hunter, I used my GPS all the time over in the Natchaug Forest and up along the Mass border where there are more pine trees in the swamps than you can shake a stick at. Never had a problem getting three satellites to obtain a fix. Maybe it is just the shape/composition of the mountains, the latitude or something but neither GPS worked worth a damn in Alaska, Idaho or the Dakotas. They were OK in Arizona and New Mexico. I have no problems in my boat either but I am never lost enough to need one poking around in the mangroves. I can't say anything other than it's worked for me. Much to my embarrassement, I was talking to a friend who is a big time deer hunter and he was telling me, unsolicited I might add, that his GPS gave him fits this weekend during bow season for deer. He was hunting my property so it wasn't a location thing. And, strangely, I've had problems with the RC400 even on open water with the receiver losing lock although that was fixed with a firmware update. I've had this opinion, based on nothing other than observation and a very megar understanding of GPS satellite communications (which is nothing like other satellite communications) that folks in the northern latitudes don't get as strong a signal as folks further south. Just this past week, I got instant locks on my car's GPS - a full spectrum of 12 satellites even time I turned it on and that was in South Carolina. Up here, it takes a good 30 seconds for it to get a 5 satelite lock to start working and the constellation is generally clustered around the satellite that traverses the North Pole at the time which limits the amount of sky available. Compared to the constellation aquired in SC which was a fairly broad spectrum of sky. Dunno. -- "Every normal man must be tempted at times to spit on his hands, hoist the black flag, and begin to slit throats." H. L. Mencken I can get lost in the Sacramento Delta without the gps. And during low waters some of the higher levies will cause lock loss. But most of the time good reception everywhere. Both the Garmin 162 and 76cx. |
Carry your compass
"D K" wrote in message ... Don White wrote: "Calif Bill" wrote in message ... "Tom Francis - SWSports" wrote in message ... On Sun, 04 Jan 2009 20:35:50 -0500, wrote: On Sun, 04 Jan 2009 19:59:03 -0500, Tom Francis - SWSports wrote: On Sun, 04 Jan 2009 19:27:49 -0500, wrote: On Sun, 4 Jan 2009 08:57:23 -0800 (PST), Frogwatch wrote: Took my daughter kayaking yesterday with my wife and I in the canoe and Katie in her kayak. Went in the salt marshes on the Gulf coast here (N. FL). We got out into an area maybe 1/4 mile wide when fog started coming in and I decided to hug shore justb in case. Sure enough, very quickly you could barely see 50'. We easily got back by following the shore but if we had been out in the middle, it would have been a problem. I did not have my compass that I normally carry in my sailing bag. From now on, compass goes with me on all trips. I keep an old boy scout style compass with me wherever I am on the water. In the boat it is handy for tracking storms. Shoot a real bearing on the edge of the cloud you are concerned about and check it again a few minutes later. That will tell you which way it is moving, relative to your course. In a "bail out" situation, a compass will help me navigate through the mangroves so I can walk home. In a bail out situation, a portable GPS is going to be a hell of a lot more informative than a compass. Although I do carry a compass, I also carry a small portable GPS - Magellan Triton 200. http://www.magellangps.com/products/....asp?segID=425 Never had a dead battery in my compass ;-) True enough, but you don't need to keep the GPS up and running the whole time either. A good set of batteries and a set of spares can last you a couple of weeks if you use the GPS properly in an emergency situation. But your point is well taken - a compass doesn't require a lot of skill. Although, just to make a point, a lot of people don't understand the difference between True and Magnetic North and that can lead to diaster in and of itself. -- Happy Holidays and Merry Whatever It Is That ****es Liberals Off. We were kayaking at Point Arena late September. Fog came in and was hard to see the shore. Couple of friends doing some filming on MLPA's come across a guy on a sort of pontoon kayak, paddling out to sea. He thought he was paddling towards the bluffs. Just a fog bluff. No radio, no GPS, no compass. Next stop Hawaii of lucky, or Asia if not. I carry a handheld GPS, a compass and a VHF when I boat. Fog is very common around here from June through July and sometimes September. In a 25hp rowboat? When is the last time you were out of sight from shore, dummy? In my 15 hp tin boat I was out of sight of the shore at 1/4 mile. fog was nasty. |
Carry your compass
On Mon, 5 Jan 2009 23:32:40 -0800, "CalifBill"
wrote: In my 15 hp tin boat I was out of sight of the shore at 1/4 mile. fog was nasty. Hey - what do you get when you smoke a cigar in the fog? SMOG!!!! BBBBAAWWWAAAHHHHHAAAAAAA!!!!! Erm.... On second thought... Never mind. -- "Far better it is to dare mighty things, to win glorious triumphs even though checkered by failure, than to rank with those poor spirits who neither enjoy nor suffer much because they live in the gray twilight that knows neither victory nor defeat." Theodore Roosevelt |
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