RDF (radio direction finding) ... do you ?
 

i know everyone uses gps. enough said.

but i also know that a lot of cruisers (most ? all ? all of the smart
ones ?!) use alternate methods of finding their position and navigating
to both keep their skills current in case of emergency, to double check
the gps equipment, etc, etc. some use celestial navigation, everyone
uses piloting skills, and on and on.

but do you still use RDF ?

if so, could you talk a little about what equipment you keep on board
for it ?

most of the RDF equipment i've seen looks really old!

RDF (radio direction finding) ... do you ?
 

On 3 Mar 2006 14:57:52 -0800, "purple_stars"
wrote:

most of the RDF equipment i've seen looks really old!

That's because it has been virtually obsolete for over 20 years, ever
since LORAN-C became widely available and affordable back in the early
'80s. Truth is, RDF was never all that accurate or reliable, it's
just that it was the only affordable electronic aide to navigation for
many years. I still have mine in the garage and I'm not expecting it
to move anytime soon. The best backup for GPS is another GPS, and
some spare batteries.

RDF (radio direction finding) ... do you ?
 

On Fri, 03 Mar 2006 23:11:04 -0500, Wayne.B
wrote:

On 3 Mar 2006 14:57:52 -0800, "purple_stars"
wrote:

most of the RDF equipment i've seen looks really old!

That's because it has been virtually obsolete for over 20 years, ever
since LORAN-C became widely available and affordable back in the early
'80s. Truth is, RDF was never all that accurate or reliable, it's
just that it was the only affordable electronic aide to navigation for
many years. I still have mine in the garage and I'm not expecting it
to move anytime soon. The best backup for GPS is another GPS, and
some spare batteries.

I have an old RDF and have wondered if it could be useful for any
purpose. For example, getting a bearing on a VHF radio transmission
from a boat in distress. Or, perhaps, getting a bearing on an AM or
FM radio tower or a FAA tower. Any conceivable use for it or fun to
be had with it, or is it time to send it to Davy Jones?

Lee Huddleston
s/v Truelove

RDF (radio direction finding) ... do you ?
 

On Sat, 04 Mar 2006 06:00:41 GMT, (Lee
Huddleston) wrote:

Any conceivable use for it or fun to
be had with it, or is it time to send it to Davy Jones?

Think of it as an overgrown AM radio, but who listens to AM radio
anymore? I haven't used my RDF in the last 20 years, and haven't even
kept it on the boat for about that long.

RDF (radio direction finding) ... do you ?
 

RDF is not without use. It saved my life in a tropical storm (or at
least made the ride a lot better) by finding the strongest T-storms for
me so I could go the other way.

But then again, I use a sextant to measure clouds to see how fast they
are rising and in what direction they are traveling :-)

RDF (radio direction finding) ... do you ?
 

purple_stars wrote:
i know everyone uses gps. enough said.

but i also know that a lot of cruisers (most ? all ? all of the smart
ones ?!) use alternate methods of finding their position and
navigating to both keep their skills current in case of emergency, to
double check the gps equipment, etc, etc. some use celestial
navigation, everyone uses piloting skills, and on and on.

but do you still use RDF ?

if so, could you talk a little about what equipment you keep on board
for it ?

most of the RDF equipment i've seen looks really old!

I thought the transmitters were switched off years ago.

RDF (radio direction finding) ... do you ?
 

RDF is nice to have if it covers the MW band, but it is very very nice to
have if it covers the VHF band. This allows you to get a bearing on other
boats, not just shore stations.
Steve

"purple_stars" wrote in message
oups.com...
i know everyone uses gps. enough said.

but i also know that a lot of cruisers (most ? all ? all of the smart
ones ?!) use alternate methods of finding their position and navigating
to both keep their skills current in case of emergency, to double check
the gps equipment, etc, etc. some use celestial navigation, everyone
uses piloting skills, and on and on.

but do you still use RDF ?

if so, could you talk a little about what equipment you keep on board
for it ?

most of the RDF equipment i've seen looks really old!

RDF (radio direction finding) ... do you ?
 

You are right. Any AM radio station can be tracked.

That is all RDF ever did and contrary to what some others have said
here it is very accurate. I use RDF for instrument approaches in
airplanes regularly. The only reason it is not used much anymore is
because it fails to give other information that other equipment can
give these days, like VOR's that can give a bearing to/from as opposed
to just to and DME that is found on most VOR sites. None of that is
really mariner equipment but since aviation is what drove a lot of the
more modern equipment, it is important because it also killed the old
gears popularity.

I mentioned in another post that I tracked lightning with an RDF. The
pulse of electricity that comes from lightning makes the needle of the
RDF jump and point toward the source of the electricity (the lightning)
It is a really great tool should you get caught out in an area of
storms and need to know where the heaviest activity is.

I was out between Swan island, Honduras and Jamaica, right out in the
middle of nowhere, the first week of June one year and sailed right
through the first tropical storm of the year. The RDF I had lead me
away from the strong cells and really did save my life. As for why I
was there, I got stuck going through the Panama Canal and really didn't
have any other choice unless i wanted to spend the summer in Panama and
Colon Panama isn't fun for a day!

RDF (radio direction finding) ... do you ?
 

On that thought, if anyone has one of those that they want to sell, I
would like to buy it.

RDF (radio direction finding) ... do you ?
 

A couple of comments.

While opinions about accuracy vary, no numbers have been posted. Come
Spring, it would be great to see a couple of sailors with RDF's take
them out of hiding and check their accuracy against their GPS.

No RDF is going to provide a position within a few meters except by
accident. but most of us work really hard to avoid needing that kind of
accuracy.

Many portable AM radios (read cheap, garage sale variety) have ferrite
antennas that are often sufficiently directional to be usable for RDF
work. Rotate the whole radio and use with a crude hand-drawn scale. It
might even be fun to use one of these "lower tech" systems. Not quite as
accurate as optical triangulation, but at least as much fun. And then
there's the added bonus of an on-board source of weather, news, "music",
and talk shows!

Good luck!

Chuck

purple_stars wrote:
i know everyone uses gps. enough said.

but i also know that a lot of cruisers (most ? all ? all of the smart
ones ?!) use alternate methods of finding their position and navigating
to both keep their skills current in case of emergency, to double check
the gps equipment, etc, etc. some use celestial navigation, everyone
uses piloting skills, and on and on.

but do you still use RDF ?

if so, could you talk a little about what equipment you keep on board
for it ?

most of the RDF equipment i've seen looks really old!

RDF (radio direction finding) ... do you ?
 

On Sun, 05 Mar 2006 14:15:42 GMT, chuck wrote:

While opinions about accuracy vary, no numbers have been posted. Come
Spring, it would be great to see a couple of sailors with RDF's take
them out of hiding and check their accuracy against their GPS.

I used to rely on an RDF back in the 70s and have a good feel for both
accuracy and the source of errors. I'm not talking about aircraft
type VHF/VOR, but rather the traditional marine HF radio type with
rotatating antenna sensor.

RDF works by providing a bearing to a known object, in this case the
radio tower which is plotted on a chart. The bearing provided by the
RDF was typically relative to the heading of the boat except for the
hand held RDFs with built in bearing compass. Either way, the
accuracy of the bearing was only as accurate as the compass used,
typically plus or minus 2 or 3 degrees.

A single bearing to a radio tower provides only a single line of
position, i.e., your boat is located somewhere along that line but you
don't know exactly where without a second LOP from another radio
station. Ideally the second bearing should cross the first at 90
degrees but in real life that hardly ever happens. The narrower the
crossing angle, the more that any bearing error is magnified, and the
more uncertainty that is introduced in your position plot.

Back to accuracy. An error of plus/minus 3 degrees at 10 nautical
miles translates to an uncertainty of plus/minus 3/10ths of a mile or
about 3600 feet in total. Taken with a 90 degree crossing angle of
the same error magnitude, you now have an uncertainty box about
6/10ths of a mile on each side. With less than ideal crossing angles
the uncertainty box elongates to as much as one or two miles in real
world situations.

Compare that to LORAN-Cs 100 yard accuracy, or GPS/WAAS at 10 feet and
make your own decision regarding RDF accuracy.

RDF (radio direction finding) ... do you ?
 

On 5 Mar 2006 08:11:31 -0800, "Da Kine"
wrote:

If someone goes off shore with the hopes that GPS is going
to do it all for them then sooner or later, they will lose their boat
and maybe their life.

That is nonsense.

There is no viable alternative offshore other than celestial, and even
the Navy has stopped teaching it.

A couple of spare GPS handhelds with some extra batteries and you are
as secure as it gets these days. You DO need to know how to use them
of course.

RDF (radio direction finding) ... do you ?
 

The USCG requires it - today - for higher licensing. It's not
nonsense. A sextant is a great tool used to measure angles and a tool I
don't go off shore without. You can get an extremely accurate fix
with a sextant and a compass with only 1 known point on the horizon.

Just because you don't see a need for something doesn't mean
anything other then you don't know how to use it. Offshore, I can
think of more then a dozen ways to navigate using nothing more then
cloud formation, wind direction and change thereof, wave height and
shape and crossing, Wave interval between crests and OH so many more.

GPS is great right up until you get a lighting strike and everything
blows out. Those that say "that'll never happen to me" have never
been sailing in the tropics. My boat was hit along with 2 other boats
with the same lighting strike. My boat was spared because I was
navigating at the time with NO POWER ON and everything disconnected at
the breakers and I had no water in my bilge. Another boat with me lost
about 20K worth of electronics and was done for the season but suffered
no damage other then electronic and the third boat was unplugged but
somehow got a smoldering spark that later that night burned the boat to
the water line. There is not much you can do about fire but the lazy
ass friend of mine that wouldn't hand steer and thought GPS was the
only answer found himself on a boat that he couldn't do a thing with
after one little strike!

Those that advocate that GPS is the second coming are fooling
themselves. I hope they stay close to some of the not so lazy mariners
so that WHEN they step in it they'll have someone to pull them out.

RDF (radio direction finding) ... do you ?
 

Maybe I am misreading - GPS is not the only tool you need and it seems
that you are saying it is. Also, that little lightning detector that's
being sold is nothing more then an RDF with no other features.

I'm not tryiing to start a brawl here, I just see people thinking to
highly of GPS. The funniest thing is that most of the charts for other
parts of the world are not nearly accurate enough to even think GPS.
There are island groups on Caribbean charts with notes like "last
survey by captain so and so of the English admiralty 1841 - No chart
datum can fix that chart. Este sud Este is about 4 miles off of the
chart position and none of the little islands are in the same place or
the same shape as on the chart. Half moon key (cayo media luna)
isn't even there anymore, there is an atoll where it use to be (but
it is still on the charts.

The point is, if you don't KNOW how to navigate you're likely to
trust the wrong thing or not trust the right thing. If you know how to
really navigate - read waves, understand currents, read clouds, know
weather, do dead reckoning, keep a log, triangulate, use a sextant -
You'll need the old tools to do time honored navigation. GPS is a great
tool as long as it works and as long as the charts are accurate (which
they aren't and which get worse as you get further away from places
people frequent - like where most people like to cruise). GPS is
great if it doesn't run you aground on the reef that was suppose to
be 4 miles away!

As for RDF - I think anyone sailing in a tropical area should have
one for the one time they need to see the direction of a lightning
storm. I also think everyone there needs a sextant and knowledge of how
to do triangulation so they can keep track of a distant storms movement
with bass height (which requires weather knowledge). I think that
anyone stuck in a problem concerning those things that has not learned
what they should know and has left sight of land without the right
tools is asking for trouble.

RDF (radio direction finding) ... do you ?
 

waynes said ...
There is no viable alternative offshore other than celestial,
and even the Navy has stopped teaching it.

waynes i'm guessing that you mean that the navy doesn't teach RDF, not
that they don't teach celestial. only reason i say that is because it
seems like the military would need backups like celestial because i
understood that the EMP from a nuclear weapons blast could take out
electronics such as GPS systems. is that wrong ? i'm surprised that
someone in the navy who was going to navigate such important ships
would be able to get out of their training without knowing absolutely
every way there was in the world to navigate. it seems like a navy
sailor would have to know everything there is to know about navigation
before they could make decisions that affect the ship.

da kine said ...
GPS is great right up until you get a lighting strike and
everything blows out.

thanks da kine and everyone for the great posts. i want to know as
much about navigation as i can and really enjoy learning about all
these alternatives. you mentioned some others including cloud
formation, wind direction, wave intervals, etc, and i hope things like
that get mentioned in the two fat navigation books i'm currently
reading.

i wonder what other situations could lead to GPS not working ? i'm
with everyone else who thinks that GPS with some spares is really
important. i agree relying on just a GPS wired into the boat is a bad
idea because what happens if it stops working, or if your boat
batteries die, or you just forget to bring enough fuses or something,
or your power generation methods fail. i can't really think of much
that would stop a handheld unit from working except for
losing/destroying them, not having batteries, etc. i wonder what
situations outside of a sailors control could make GPS fail ? i mean,
i assume because so many people rely on GPS that the military wouldn't
just shut it off unless there was some really drastic reason for doing
so. i've read that they might make it more inaccurate or shut it off
in the event of war, would they ? and i assume too that they take
really good care of it since they and everyone relies on it so much ...
has it ever failed ?

RDF (radio direction finding) ... do you ?
 

As I understand it, they actually run off of a gyro system that is
better then GPS. Also, I have a good friend that captains a navy sub
that told me celestial navigation was required.

In your reading, pick up a red/orange colored paperback called
“Emergency Navigation�. Its available all over and you should be
able to find it at http://www.amazon.com for cheap. You won’t find
much of the good stuff in most books.

As for something else making GPS not work, there are a few things I
have come across and here they are.

On 9/11 GPS was scrabbled in many areas. For anyone in a critical
position in one of the scrabbled areas, OOPS!

In Mexico (and I love this one) I ran across and “electrical
engineer� that had a broken GPS and his spare didn’t work either.
This was a while back but … Turned out to be a bad antenna that I
fixed for him – the engineer☺

That’s the only way gps failures other then lighting that I know of.

As for a spare GPS, the rumor is that if you wrap a handheld in tinfoil
and get hit by lightning, your spare will still work. I don’t know
anyone that has put it to the test but I keep my spare wrapped just the
same.

GPS signals use to be scrabbled all the time. In about 1991 or so the
military started allowing public access of the gps signal. In times of
heightened defense alerts, the gps signal does get less accurate but
then there is also a differential signal that I don’t know much about
but is used to help the gps become more accurate again. All in all,
I’m more worried about lightning, having been through enough of it,
then anything else.

RDF (radio direction finding) ... do you ?
 

Da Kine wrote:
[snip]
In your reading, pick up a red/orange colored paperback called
"Emergency Navigation". Its available all over and you should be
able to find it at http://www.amazon.com for cheap. You won't find
much of the good stuff in most books.

good stuff, i will check into it ...

As for something else making GPS not work, there are a few things I
have come across and here they are.

i spent a little while reading about this since my last post and found
some interesting things i didn't know, i'll post some of them here
since you are interested too! from some of the things i read it looks
like GPS does/has failed before, i didn't know that before now.
there's a quote in one of these documents that i found interest, the
document says the quote is from "Interagency GPS Executive Board. GPS
policy, applications, modernization, international cooperation.
February 01". here's what it says ...

"GPS provides many benefits to civilian users. It is vulnerable,
however, to interference and other disruptions that can have harmful
consequences. GPS users must ensure that adequate independent backup
systems or procedures can be used when needed."

then later in that same document it is talking about situations where
GPS doesn't work, and apparently it's pretty easy to make it not work!
you can build GPS jammers using plans on the net to jam GPS signals,
and there are even jammers sold for doing the same thing. one paper i
read said that these jammers are sold to militaries that want to be
able to selectively jam areas for security reasons, and to defend
themselves from attack, and that some of these jammers are huge like
radio stations.

this one paper i read had these real world situations where GPS had
failed ...

"Jamming in Mesa, AZ
13 - 18 Dec 01, GPS jammer caused GPS failures within 180nm of Mesa,
AZ
Boeing was preparing for upcoming test
Accidentally left Jammer on L1 frequency radiating at .8mW
Jammer operated continuously for 4.5 days
Impact to ATC operations
A/C lost GPS 45nm from PHX, performed 35° turn toward traffic
NOTAM was not issued until 2nd day
Numerous pilots reported loss of GPS NavAid
Reports of hand-held GPS receivers not working"

"Jamming in Moss Landing Harbor, CA
15 Apr 01 - 22 May 01, VHF/UHF television antenna with pre-amplifier
caused GPS failures to all of Moss Landing Harbor
Boat owner purchased TV antenna, which was equipped with pre-amp
From interior location Amp's emitter jammed all of Moss Harbor and
1km out to sea
No GPS in entire area = 37 days
Impact to Moss Harbor
Research vessels relied heavily on timing from GPS
Extreme difficulty going through harbor in foggy conditions
Notification to all vessels in area that GPS was down
Switched back to radar control for harbor entrances"

the source for those was a document from a search engine with the title
"Civilian GPS Systems and Potential Vulnerabilities"

i also read online that geomagnetic storms can cause GPS to fail,
especially in higher latitudes and during periods of intense solar
activity. it said that storms can introduce errors of 1km and more
depending on location and how active the ionosphere is. and then there
are other kinds of errors too that i read about, ones that seem well
known to people who are really into that kind of thing.

thinking back on it, i also remember another reference to GPS failure,
somewhere in the red sea or east coast of africa there was a harbor
where GPS doesn't work, but now i can't remember where i read it. i
think it may have been in jimmy cornell's "world cruising handbook" but
i glanced through it just now and couldn't find the reference.
apologies to the author if i am wrong about that!

i guess like anything else, GPS is just another aide to navigation.

RDF (radio direction finding) ... do you ?
 

These are great examples of why I keep up on my other nav skills and
why I make a point to bust the chops of the guys that try to preach gps
like they do.

As well intentioned as people are, they are blindly falling into a trap
and leading others with them when they set aside the old world skills
of navigation.

Good for you for being smart!

RDF (radio direction finding) ... do you ?
 

I meant that I really might have misread your post. The way I read it
said to me that you were saying gps is the way, and only way. Sorry
that you thought I was being a jerk - I didn't want to come off like
that.

RDF (radio direction finding) ... do you ?
 

chuck wrote:
A couple of comments.

While opinions about accuracy vary, no numbers have been posted. Come
Spring, it would be great to see a couple of sailors with RDF's take
them out of hiding and check their accuracy against their GPS.

No RDF is going to provide a position within a few meters except by
accident. but most of us work really hard to avoid needing that kind of
accuracy.

i'm going to try it. :)

i'm just going to get some of this RDF equipment and try it out on land
while using my handheld GPS and some maps to check against. or maybe
in the truck, i have an icom radio in the truck i can use with an
antenna, it has a strength meter built into it. i'll have to find a
good directional antenna to use, or make one. i'm going to check
around for some of the actual RDF equipment used in marine navigation
too though, i bet there is tons of this stuff in people's garages just
waiting for someone to find. when i was reading it looks like you can
also find old RDF/ADF equipment out of old airplanes too to play with,
and these have needles that turn to whatever transmitter is using the
frequency you tune too! fun stuff.

RDF (radio direction finding) ... do you ?
 

Take a look in your local library for a copy of the Radio Amateur's
Handbook. You'll find a discussion there on building small loop antennas
that can be pretty effective in RDF work.

Another option is to check Ebay from time to time for used RDF gear.
Heathkit made a lot of marine RDF units over the years and these are
usually priced reasonably.

Good luck!

Chuck

purple_stars wrote:


i'm going to try it. :)

i'm just going to get some of this RDF equipment and try it out on land
while using my handheld GPS and some maps to check against. or maybe
in the truck, i have an icom radio in the truck i can use with an
antenna, it has a strength meter built into it. i'll have to find a
good directional antenna to use, or make one. i'm going to check
around for some of the actual RDF equipment used in marine navigation
too though, i bet there is tons of this stuff in people's garages just
waiting for someone to find. when i was reading it looks like you can
also find old RDF/ADF equipment out of old airplanes too to play with,
and these have needles that turn to whatever transmitter is using the
frequency you tune too! fun stuff.

RDF (radio direction finding) ... do you ?
 

Wayne.B wrote:
On 5 Mar 2006 08:11:31 -0800, "Da Kine"
wrote:


If someone goes off shore with the hopes that GPS is going
to do it all for them then sooner or later, they will lose their boat
and maybe their life.


That is nonsense.

I sort of agree. The vast majority of bozos out there never lose a
boat. But, relying completely on GPS does increase your odds of
misadventure. Those who habitually employ alternatives are safer.


There is no viable alternative offshore

It isn't "offshore" that's important. You can be 50 miles off course
in the middle of the ocean without problem; its only when you approach
land that there is an issue.


other than celestial, and even
the Navy has stopped teaching it.

Urban Myth. Of course they still teach it, and its required for many
majors. I'm sure, however, that they do not spend as much time on it
as they used to.



A couple of spare GPS handhelds with some extra batteries and you are
as secure as it gets these days. You DO need to know how to use them
of course.

On this I think you're dead wrong in piloting situations. I'm not
saying I'd throw away my GPS (or the spare) but only a fool ignores a
depth sounder, compass bearings, log, radar, etc.

RDF (radio direction finding) ... do you ?
 

Da Kine wrote:
The USCG requires it - today - for higher licensing. It's not
nonsense. A sextant is a great tool used to measure angles and a tool I
don't go off shore without. You can get an extremely accurate fix
with a sextant and a compass with only 1 known point on the horizon.

Just because you don't see a need for something doesn't mean
anything other then you don't know how to use it. Offshore, I can
think of more then a dozen ways to navigate using nothing more then
cloud formation, wind direction and change thereof, wave height and
shape and crossing, Wave interval between crests and OH so many more.

GPS is great right up until you get a lighting strike and everything
blows out. Those that say "that'll never happen to me" have never
been sailing in the tropics. My boat was hit along with 2 other boats
with the same lighting strike. My boat was spared because I was
navigating at the time with NO POWER ON and everything disconnected at
the breakers and I had no water in my bilge. Another boat with me lost
about 20K worth of electronics and was done for the season but suffered
no damage other then electronic and the third boat was unplugged but
somehow got a smoldering spark that later that night burned the boat to
the water line. There is not much you can do about fire but the lazy
ass friend of mine that wouldn't hand steer and thought GPS was the
only answer found himself on a boat that he couldn't do a thing with
after one little strike!

Those that advocate that GPS is the second coming are fooling
themselves. I hope they stay close to some of the not so lazy mariners
so that WHEN they step in it they'll have someone to pull them out.

That same bolt of lightening will take out your calculator so you then
have to work stars long hand. It'll also kill your digital watch and
radio so you won't have the correct time. It'll probably short out your
boat so you won't be able to work the stars out until light the next
morning. The lightening excuse to learn astro is BS. Learn it because
you want to or take a couple extra handheld GPS. Practice dead
reckoning. Know where you are all the time.

Gaz

RDF (radio direction finding) ... do you ?
 

Da Kine wrote:
Maybe I am misreading - GPS is not the only tool you need and it seems
that you are saying it is. Also, that little lightning detector that's
being sold is nothing more then an RDF with no other features.

I'm not tryiing to start a brawl here, I just see people thinking to
highly of GPS. The funniest thing is that most of the charts for other
parts of the world are not nearly accurate enough to even think GPS.
There are island groups on Caribbean charts with notes like "last
survey by captain so and so of the English admiralty 1841 - No chart
datum can fix that chart. Este sud Este is about 4 miles off of the
chart position and none of the little islands are in the same place or
the same shape as on the chart. Half moon key (cayo media luna)
isn't even there anymore, there is an atoll where it use to be (but
it is still on the charts.

The point is, if you don't KNOW how to navigate you're likely to
trust the wrong thing or not trust the right thing. If you know how to
really navigate - read waves, understand currents, read clouds, know
weather, do dead reckoning, keep a log, triangulate, use a sextant -
You'll need the old tools to do time honored navigation. GPS is a great
tool as long as it works and as long as the charts are accurate (which
they aren't and which get worse as you get further away from places
people frequent - like where most people like to cruise). GPS is
great if it doesn't run you aground on the reef that was suppose to
be 4 miles away!

As for RDF - I think anyone sailing in a tropical area should have
one for the one time they need to see the direction of a lightning
storm. I also think everyone there needs a sextant and knowledge of how
to do triangulation so they can keep track of a distant storms movement
with bass height (which requires weather knowledge). I think that
anyone stuck in a problem concerning those things that has not learned
what they should know and has left sight of land without the right
tools is asking for trouble.

Tell mw how you fix your position on a chart, surveyed in 1841, without
a known datum, using waves, clouds and a sextant?

RDF (radio direction finding) ... do you ?
 

Da Kine wrote:
As I understand it, they actually run off of a gyro system that is
better then GPS. Also, I have a good friend that captains a navy sub
that told me celestial navigation was required.

In your reading, pick up a red/orange colored paperback called
“Emergency Navigation�. Its available all over and you should be
able to find it at http://www.amazon.com for cheap. You won’t find
much of the good stuff in most books.

As for something else making GPS not work, there are a few things I
have come across and here they are.

On 9/11 GPS was scrabbled in many areas. For anyone in a critical
position in one of the scrabbled areas, OOPS!

In Mexico (and I love this one) I ran across and “electrical
engineer� that had a broken GPS and his spare didn’t work either.
This was a while back but … Turned out to be a bad antenna that I
fixed for him – the engineer☺

That’s the only way gps failures other then lighting that I know of.

As for a spare GPS, the rumor is that if you wrap a handheld in tinfoil
and get hit by lightning, your spare will still work. I don’t know
anyone that has put it to the test but I keep my spare wrapped just the
same.

GPS signals use to be scrabbled all the time. In about 1991 or so the
military started allowing public access of the gps signal. In times of
heightened defense alerts, the gps signal does get less accurate but
then there is also a differential signal that I don’t know much about
but is used to help the gps become more accurate again. All in all,
I’m more worried about lightning, having been through enough of it,
then anything else.

It's scrambled not scrabbled and they never were. The error was called
selective availablity. It made the more accurate signal only available
to military users. It has long since been discontinued because the
commercial sector came up with ways to make GPS very accurate without
SA. (Differential, WAAS etc)

As far as wrapping a GPS up in tinfoil. That is a good idea. It is
also helpfull to line your ball cap with tinfoil so aliens can't see
what you are thinking.

RDF (radio direction finding) ... do you ?
 

purple_stars wrote:
Da Kine wrote:
[snip]

In your reading, pick up a red/orange colored paperback called
"Emergency Navigation". Its available all over and you should be
able to find it at http://www.amazon.com for cheap. You won't find
much of the good stuff in most books.


good stuff, i will check into it ...


As for something else making GPS not work, there are a few things I
have come across and here they are.


i spent a little while reading about this since my last post and found
some interesting things i didn't know, i'll post some of them here
since you are interested too! from some of the things i read it looks
like GPS does/has failed before, i didn't know that before now.
there's a quote in one of these documents that i found interest, the
document says the quote is from "Interagency GPS Executive Board. GPS
policy, applications, modernization, international cooperation.
February 01". here's what it says ...

"GPS provides many benefits to civilian users. It is vulnerable,
however, to interference and other disruptions that can have harmful
consequences. GPS users must ensure that adequate independent backup
systems or procedures can be used when needed."

then later in that same document it is talking about situations where
GPS doesn't work, and apparently it's pretty easy to make it not work!
you can build GPS jammers using plans on the net to jam GPS signals,
and there are even jammers sold for doing the same thing. one paper i
read said that these jammers are sold to militaries that want to be
able to selectively jam areas for security reasons, and to defend
themselves from attack, and that some of these jammers are huge like
radio stations.

this one paper i read had these real world situations where GPS had
failed ...

"Jamming in Mesa, AZ
13 - 18 Dec 01, GPS jammer caused GPS failures within 180nm of Mesa,
AZ
Boeing was preparing for upcoming test
Accidentally left Jammer on L1 frequency radiating at .8mW
Jammer operated continuously for 4.5 days
Impact to ATC operations
A/C lost GPS 45nm from PHX, performed 35° turn toward traffic
NOTAM was not issued until 2nd day
Numerous pilots reported loss of GPS NavAid
Reports of hand-held GPS receivers not working"

"Jamming in Moss Landing Harbor, CA
15 Apr 01 - 22 May 01, VHF/UHF television antenna with pre-amplifier
caused GPS failures to all of Moss Landing Harbor
Boat owner purchased TV antenna, which was equipped with pre-amp
From interior location Amp's emitter jammed all of Moss Harbor and
1km out to sea
No GPS in entire area = 37 days
Impact to Moss Harbor
Research vessels relied heavily on timing from GPS
Extreme difficulty going through harbor in foggy conditions
Notification to all vessels in area that GPS was down
Switched back to radar control for harbor entrances"

The jamming of GPS is possible and used. The challenge is long range
jamming or continuous jamming. It takes a great deal of power to jam a
GPS that is any distance away. It also needs to run continuously to
really screw you up. Once the jamming stops, or you get too far away,
it just locks back on. The jamming will likely be obvious. You just
won't get a signal. The better way of doing it is not jamming but
deceiving the GPS so it looks like it is working but leads you (or a
missile) away from the intended destination or target. This would be
fairly obvious on a yacht at sea.

In other words, don't worry about it. The 90% of the time you are on
your boat sitting at anchor it won't matter. The rest of the time
nobody cares to jam you.

Don't forget that tinfoil in your ball cap.

RDF (radio direction finding) ... do you ?
 

On 5 Mar 2006 10:36:28 -0800, "Da Kine"
wrote:

GPS is great right up until you get a lighting strike and everything
blows out. Those that say "that'll never happen to me" have never
been sailing in the tropics. My boat was hit along with 2 other boats
with the same lighting strike.

Can you envision one or two spare hand heldt GPS units that are
battery operated? They only cost about $100 each these days, and are
at least 100 times more accurate than a celestial fix, and usually
acquire position in less than a minute, any time of day, and in any
weather. With all due respect to celestial, it is a relic at this
point and you are riding a dead horse.

I navigated a 50 ft sloop 300 nautical miles into Bermuda with a hand
held GPS over 10 years ago after taking a lightening strike that
knocked out all installed electronics. No big deal.

RDF (radio direction finding) ... do you ?
 

On 5 Mar 2006 14:20:24 -0800, "purple_stars"
wrote:

waynes i'm guessing that you mean that the navy doesn't teach RDF, not
that they don't teach celestial. only reason i say that is because it
seems like the military would need backups like celestial because i
understood that the EMP from a nuclear weapons blast could take out
electronics such as GPS systems. is that wrong ?

Yes, it's wrong. They no longer teach celestial. The military buys
EMP hardened electronics, and has for a long time.

RDF (radio direction finding) ... do you ?
 

On 5 Mar 2006 11:00:41 -0800, "Da Kine"
wrote:

I've been a commercial pilot for something like 16 years and I have
had more equipment failures then I can remember. I've never had a
serious problem because every plane I have flown has had at least 2 of
everything.

My boat has two of everything that is important, sometimes three.

RDF (radio direction finding) ... do you ?
 

On Mon, 06 Mar 2006 01:57:32 GMT, chuck wrote:

Heathkit made a lot of marine RDF units over the years and these are
usually priced reasonably.

Good grief, they should be free.

RDF (radio direction finding) ... do you ?
 

On Sun, 05 Mar 2006 21:42:58 -0500, Jeff wrote:

On this I think you're dead wrong in piloting situations. I'm not
saying I'd throw away my GPS (or the spare) but only a fool ignores a
depth sounder, compass bearings, log, radar, etc.

Of course, indispensible for coastal piloting.

The original statement that I rebutted was that "no one should rely
solely on GPS when OFFSHORE".

Where I come from offshore means off soundings, and the only thing you
will see on your radar is other boats.

Dead reckoning is fine but after several days OFFSHORE you will be
lucky if your DR plot is within 10 miles of actual.

I stand by my statement, there are no viable OFFSHORE alternatives to
GPS.

RDF (radio direction finding) ... do you ?
 

Wayne.B wrote in
:

On Sun, 05 Mar 2006 21:42:58 -0500, Jeff wrote:

On this I think you're dead wrong in piloting situations. I'm not
saying I'd throw away my GPS (or the spare) but only a fool ignores a
depth sounder, compass bearings, log, radar, etc.

Of course, indispensible for coastal piloting.

The original statement that I rebutted was that "no one should rely
solely on GPS when OFFSHORE".

Where I come from offshore means off soundings, and the only thing you
will see on your radar is other boats.

Dead reckoning is fine but after several days OFFSHORE you will be
lucky if your DR plot is within 10 miles of actual.

I stand by my statement, there are no viable OFFSHORE alternatives to
GPS.



Gee, I wonder how I navigated all over the world, offshore, prior to GPS,
if I had no viable alternative to GPS.

otn

RDF (radio direction finding) ... do you ?
 

That same bolt of lightening will take out your calculator so you then
have to work stars long hand. It'll also kill your digital watch and
radio so you won't have the correct time. It'll probably short out your
boat so you won't be able to work the stars out until light the next
morning. The lightening excuse to learn astro is BS. Learn it because
you want to or take a couple extra handheld GPS. Practice dead
reckoning. Know where you are all the time.

Gaz

Let's see...... calculator gone, long hand star calc's....add a minute or
two to the solution.
digital watch killed..... in that case I'm probably dead too so what do I
care.... always have a mechanical clock that you know the error...no big
deal, was done for years.
lights out?....lite a candle or wait till daylight.... what the hell, it's
offshore navigation, what's the rush....

RDF (radio direction finding) ... do you ?
 

Well, Genius, Weather is a predicable navigation tool. I'd teach you
but then you would have to admit you were wrong and self proclaimed
geniuses are never wrong. Weather, waves, currents, shape of waves and
much more can be used to accurately navigate. The south Pacific
mariners used that form of navigation very efficiently as do I.

RDF (radio direction finding) ... do you ?
 

Why is it that you don't like the idea of needing to know/learn
something?
My watch never got hurt when we were hit. My clock never got hurt. My
TV that had a clock didn't get hurt but that clock sped up. NOTHING
WAS HURT because I knew when to turn the power off and navigate like a
sailor!

As for celestial, I think I made a point that I use my sextant more for
weather observation then anything else, but I have ALWAYS done my math
longhand on paper. If you don't, you don't know celestial.
Computers are great, I'm on one now, but I trust paper charts, and
old school learning.

The lightning excuse is not BS. Fighting someone who recommends being
smarter is BS. This is why I only come here once in a while, that and
the fact that I am more often then not out to sea as I will be in a few
weeks. I'm sorry if I stepped on your only chance to feel important.
I was giving information to someone that wanted to learn and someone
that might actually go sailing and lose sight of land. You don't need
to stick your head in to protect anything. I will be out sailing again
soon and your little domain will be yours again to spread stupidly with
your other slip sailing friends.

Keep your armchair warm and stay dry. You're suited for it.

RDF (radio direction finding) ... do you ?
 

You didn't navigate, your gps did. I'm very glad you made it safely but
get real. If you don't know something, don't be proud of it. I can do
anything you can with a gps but can you do what I can? If not, why
not? You life is not the only one you are responsible for when you are
out there. If you need something, ever, and don't have it to use, and
it was easy to get, how stupid are you.

These things fall into the same thought train as thoughts I give my
pilot students - you can never use runway behind you, gas in the truck,
altitude above you, and in this case, knowledge in someone else's head.

RDF (radio direction finding) ... do you ?
 

You have not sailed much then. Where I come from, water can be 2 feet
deep and there hasn't been land in sight for a long long time. Sail the
Caribbean, Maldives, South Pacific, or any of many other areas where
reef and rock is just waiting to bite you in your butt.

I also never said to try to dead recon anywhere. I said you sure as
hell better know how if you need to!

Navigation is using all means to know where you are at all times. I use
a gps and I double check my position with what ever is available, then
I check it on my chart to be sure everything agrees and I log it with
the current weather conditions and I do it every half hour when my
timer goes off. If you use one thing and trust it, how smart are you?

You want to turn some sort of table with your side handed comments but
you really should be open to a little learning. You're not the only
one you could kill. Arrogance is not praiseworthy. What have you got
against learning something or at least letting someone else learn it.

If you don't understand it, it doesn't make it worthless.

RDF (radio direction finding) ... do you ?
 

Da Kine wrote:
Differential, WAAS and so on only work in certain areas where it is
transmitted. It does not work, as far as I know, in most of the
cruising grounds like The Bahamas and south. If I am wrong, correct me
but I am pretty sure about that.

Certainly the DGPS and WAAS is more reliable and more widely available
than waves and clouds for navigation.

But neither are critical unless you need to know where you are down to
two or three yards. Even GPS without SA shut off was good enough for
most users.


There is one way to counter a strike that is well known. It is to cover
your building with chicken wire. Doing so lets the current go around
what is inside. Tinfoil does the same thing (so we hope). I stated that
I don't know anyone that has first hand knowledge of a strike and
tinfoil. Unless you know of someone that lost a gps that was wrapped in
foil from a strike, please refrain from being so predictably newsgroup
anal. There is good information to be had and most everyone has
surprisingly behaved themselves. Do you really want to be the one who
knows everything except doesn't?

You cover your boat with chicken wire and don't forget the ball cap.

RDF (radio direction finding) ... do you ?
 

Da Kine wrote:
Well, Genius, Weather is a predicable navigation tool. I'd teach you
but then you would have to admit you were wrong and self proclaimed
geniuses are never wrong. Weather, waves, currents, shape of waves and
much more can be used to accurately navigate. The south Pacific
mariners used that form of navigation very efficiently as do I.

Tell me where you went navigating by weather.

RDF (radio direction finding) ... do you ?
 

otnmbrd wrote:
That same bolt of lightening will take out your calculator so you then
have to work stars long hand. It'll also kill your digital watch and
radio so you won't have the correct time. It'll probably short out your
boat so you won't be able to work the stars out until light the next
morning. The lightening excuse to learn astro is BS. Learn it because
you want to or take a couple extra handheld GPS. Practice dead
reckoning. Know where you are all the time.

Gaz


Let's see...... calculator gone, long hand star calc's....add a minute or
two to the solution.
digital watch killed..... in that case I'm probably dead too so what do I
care.... always have a mechanical clock that you know the error...no big
deal, was done for years.
lights out?....lite a candle or wait till daylight.... what the hell, it's
offshore navigation, what's the rush....
And how did you check the error on that deck watch? Radio? What was the
error and how much does it change daily? Can't just do the time check
anymore. Damn lightening.