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Old 02-08-2014, 02:36   #181
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Re: What will Happen to you when GPS goes Down

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Originally Posted by robert sailor View Post
If you are doing short hops or coastal cruising weather is seldom an issue if you do your homework but crossing oceans is a different thing. The really big weather systems like hurricanes will be seen days ahead but many times a low can develop very quickly and an average sailboat does not have the speed to avoid it. I have had several occasions where the actual and forecast weather were not even close so its not uncommon and then you better have some decent skills bendi toy or otherwise.
Don't disagree but there are too many sailors out there IMHO who, with 5 days of warning (they didn't know about or couldn't interpret) spent 5 days sailing 500 miles in the unsafe direction vs. the safe direction.

And I don't think the short passages are bereft of sailors getting into weather trouble. There was just a thread here of a couple plucked off and towed in from 130 miles because they were "tired."

Many folks on that thread were of the, "The should have HTFU (Hardened the Frick Up) and soldiered on." Traditional seamanship BS.

I was thinking - Were the conditions forecast and should they have even been out there?
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Old 02-08-2014, 05:37   #182
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Re: What will Happen to you when GPS goes Down

So I need to work on my weather control ....................... Hey wouldn't that make me some king of god? :-)


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Old 02-08-2014, 07:39   #183
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Re: What will Happen to you when GPS goes Down

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Originally Posted by Jammer Six View Post
You only need to take down one.
Will you explain this more?

According to this: Wired 11.05: START

the system can withstand the loss of several satellites before failure: "GPS can withstand the loss of several satellites before becoming completely dysfunctional, says Owen Wormser, who oversees space communications issues from his post in the Office of the Assistant Secretary of Defense."

Also, GPS satellites are taken off-line regularly for various reasons.

And that is just the US system. One would also need to knock out others.

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Old 02-08-2014, 07:42   #184
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Re: What will Happen to you when GPS goes Down

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You only need to take down one.

That is utter nonsense...unless it was meant as a joke.
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Old 02-08-2014, 07:43   #185
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Re: What will Happen to you when GPS goes Down

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So I need to work on my weather control ....................... Hey wouldn't that make me some king of god? :-)
One possibility. The others appear to be evil mad scientist or mutant freak.

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Old 02-08-2014, 09:14   #186
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Re: What will happen to you when gps goes down

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Originally Posted by Factor View Post
A GPS doesn't track you - you do understand that don't you, its not a transmitter, only a receiver. And the only information it receives is is the time signal from individual satellites.
Yes but you can give it different time signals and almanac data so it thinks it is somewhere else. Given that satellites are in orbit and at least 400 miles away it is easy to overpower their signal with your own.
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Old 02-08-2014, 09:20   #187
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Re: What will Happen to you when GPS goes Down

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Originally Posted by SURV69 View Post
About the am radio and null.

This is new to me, but it makes sense ... to a point.

I would think one would have to know the ferret(I forget how to spell it) antenna's orientation.

What kink of antenna is in those really ... really small am radios?
It is an iron bar (Ferrite) with a conducting wire wrapped around it. The wire is the antenna, it senses the magnetic part of radio waves rather than the electrical part that a whip antenna senses.

Since the transmitting antenna is always oriented vertically and drives the electrical component of the radio wave the magnetic component will always be horizontal. The longer the core is the more sensitive a receiver it is. The speaker always faces horizontally from a radio so you can figure out which way is up on the receiver. And the electronics are on a flat circuit board which tends to make the radio bigger in one direction than the other. So the long horizontal direction of the radio when upright is probably the orientation of the ferrite core. The null will be received when the short direction of the radio is pointing towards the transmitter. Keep in mind that there are 2 nulls or low spots that are in opposite directions.

They are shorter than whip antennae and quite a bet less susceptible to damage.

Bigger is better for sensing direction, better direction resolution, but smaller works OK, the null or quiet spot is wider though.
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Old 02-08-2014, 09:21   #188
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Re: What will happen to you when gps goes down

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Yes but you can give it different time signals and almanac data so it thinks it is somewhere else. Given that satellites are in orbit and at least 400 miles away it is easy to overpower their signal with your own.

It is not "easy". This threat is mainly from nation states and is shouldn't be a concern for cruisers not sailing in disputed areas.
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Old 02-08-2014, 09:34   #189
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Re: What will Happen to you when GPS goes Down

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Originally Posted by colemj View Post
One possibility. The others appear to be evil mad scientist or mutant freak.



Mark

Why chose

How about evil mad mutant freak scientist?

I'll change my avatar later


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Old 02-08-2014, 09:39   #190
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Re: What will happen to you when gps goes down

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It is not "easy". This threat is mainly from nation states and is shouldn't be a concern for cruisers not sailing in disputed areas.
Nation states and bored engineering students. "Easy" is very relative to who you are. Not easy for you and me, yes. Maybe not even easy for a bunch of pointy end of the bell curve types, but not terribly difficult either, especially if they are not being challenged by something else.

$80 million yacht hijacked by students spoofing GPS signals | Naked Security
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Old 02-08-2014, 10:06   #191
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Re: What will happen to you when gps goes down

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Nation states and bored engineering students. "Easy" is very relative to who you are. Not easy for you and me, yes. Maybe not even easy for a bunch of pointy end of the bell curve types, but not terribly difficult either, especially if they are not being challenged by something else.

$80 million yacht hijacked by students spoofing GPS signals | Naked Security
But they had to do it from on board the vessel. Even assuming that it has a range of 30 miles or so, who cares?
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Old 02-08-2014, 10:10   #192
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Re: What will Happen to you when GPS goes Down

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Why chose

How about evil mad mutant freak scientist?

I'll change my avatar later
You don't also want to be a god? Why leave that open for another?

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Old 02-08-2014, 10:35   #193
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Re: What will Happen to you when GPS goes Down

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There are two very unlikely reasons the military will shut down the civilian (C/A signal) GPS or severely degrade its accuracy.

Thousands of civilian agencies use it for law enforcement and emergency purposes. Commercial aircraft use it now, although not dependent on it at this point in time.

It would be pointless to deny GPS to any enemies which also have access to GLONAST.


I do believe that mariners should have multiple ways of obtaining a fix and be proficient at it.
Now there's a scary thought for ya!

Anyway, I believe the right tack is the one put out by the guy who said "worry about the five percent" - cuz the rest is in the hands of Allah. For the super-worry-warts, just throw an inexpensive plastic or aluminum sextant ($200) into a drawer and use your (very) convenient GPS to go sailing. Meantime, if you really do wake up on doomsday - you WILL learn to use the sextant!
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Old 02-08-2014, 10:56   #194
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Re: What will Happen to you when GPS goes Down

Most people use their sextant way too often as it is!
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Old 02-08-2014, 12:30   #195
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Re: What will Happen to you when GPS goes Down

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Now there's a scary thought for ya!



Anyway, I believe the right tack is the one put out by the guy who said "worry about the five percent" - cuz the rest is in the hands of Allah. For the super-worry-warts, just throw an inexpensive plastic or aluminum sextant ($200) into a drawer and use your (very) convenient GPS to go sailing. Meantime, if you really do wake up on doomsday - you WILL learn to use the sextant!


I would venture that if you do wake up on domesday that least of your worries will be determining your position.

Dave
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