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.

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.

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

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?

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.

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.

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.

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.

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.

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.