Call Search
     

New to Ham Radio?
My Profile

Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question

Operating
Contesting
DX Cluster Spots
Propagation

Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net

   Home   Help Search  
Pages: Prev 1 2 [3] 4 Next   Go Down
  Print  
Author Topic: real north versus magnetic north  (Read 8041 times)
VE9AAE
Member

Posts: 26




Ignore
« Reply #30 on: March 06, 2012, 08:43:37 PM »

W8JX,
Make no mistake, I appriciate the use of a GPS for vehicle use andnav. checks (mine has topo maps as well) but to me, on foot nothing beats a compass (graduated in mils of course!).

73 de VE9AAE
Logged
NJ3U
Member

Posts: 122




Ignore
« Reply #31 on: March 07, 2012, 05:35:39 AM »

Wim,  as I read over your post I especially appreciated one point you made regarding bandwidth.  Along that line of thought,
The best path for any given QSO may be offset from the calculated heading path.  I use the pathways show on sites like QRZ for the dx station as a starting point and then check for best sig strength several degrees on both sides of the "idea" heading.  Radio waves are influenced by many factors on their trip between send and receiving stations.
Thnx for the nice magnetic declination maps, I've downloaded them to the achieves.
73 KC2UML Rory
Logged
KCJ9091
Member

Posts: 0




Ignore
« Reply #32 on: March 07, 2012, 08:24:25 AM »

The method that works without an accurate time reference or without having to wait for noon is:


Take a stick about 24" long
put it in the ground as near to vertical as possible
mark the tip of the shadow
wait 15-30 minutes or longer, the longer the more accurate the measurment
mark the shadow again
draw a line between the marks
that line points east-west. 

Logged
W8JX
Member

Posts: 5492




Ignore
« Reply #33 on: March 07, 2012, 09:24:25 AM »

W8JX,
Make no mistake, I appriciate the use of a GPS for vehicle use andnav. checks (mine has topo maps as well) but to me, on foot nothing beats a compass (graduated in mils of course!).

73 de VE9AAE


Well make no mistake I was using hand held GPS units long before there was car ones for road navigation and it blows a compass away here. With a modern hand help mapping unit with TOPO maps installed it does not get any better. (they make Marine maps too) I can also record and track were I have been and overlay that info on a maps or satellite view for future reference. I used to use a good compass and maps but not anymore. I still carry some maps for reference but GPS will show me exactly were I have been, where I am and where I am going. I can also easily track back too. Great when hunting to record best routes into a remote area. I can pick a random point in a remote area on and get there exactly within 10 feet or less and also meet others there reliably who take different routes but are also using GPS units.
« Last Edit: March 07, 2012, 09:51:16 AM by W8JX » Logged

--------------------------------------
Entered using a  WiFi Win 8.1 RT tablet or a Android tablet using 4G/LTE or WiFi.
WB6THE
Member

Posts: 128




Ignore
« Reply #34 on: March 12, 2012, 09:20:26 AM »

At no time is the sun ever directly overhead in the 48 states.
One way to find geographical (true) north is to use a program
that gives the sun's azimuth (map direction). One such program
is ORBITRON which is free and available. Do a web search for it.

Configure the program with your lat/long and set the computer clock
accurately with WWV.

Next, rig up something vertical. Your tower will do if its perfectly vertical
otherwise suspend a heavy weight on a piece of string or thick length
of wire, line... whatever. You'll need the shadow of the string so whatever
method you use to suspend the string shouldn't cast a shadow that gets
in the way. It's difficult to push a stick in the ground and be 100% sure it is
vertical.

You can set ORBITRON to "simulate" mode so you'll know what time to make
your witness mark or just wait until the moment when the azimuth readout is
180 degrees. The string will cast a shadow toward geographical (true) north. Extend
the line cast by the shadow and bingo, north/south reference. A line 90 degrees
to your north/south reference is west/east at latitude of your QTH.
Orbitron is also a fine, yet simple satellite tracking program which uses the
two-line NASA format for it Kepler data. And it has a rotor control feature of some sort.
It shows moon data as well.

Anyway, my 1 *  10^-2 worth.

WB6THE
Alan
Logged
KC2RGW
Member

Posts: 287


WWW

Ignore
« Reply #35 on: March 12, 2012, 01:05:19 PM »

So a dumb question about the declination figures.

If I'm looking at a compass and I'm pointing at true North, but declination for the area from NOAA is 10 degrees, does that mean +10 deg is true North or does it mean that 350 degrees is true north?

It wasn't particularly clear having nothing else to refer to.
Logged
WB6BYU
Member

Posts: 13043




Ignore
« Reply #36 on: March 12, 2012, 03:37:18 PM »

I always imagine that the Magnetic North Pole is in Hudson's Bay so (from the West Coast
of the US) my compass needle would point further Right (East) that true north.  That means
that, here in Oregon, I would set the needle to point to 16 degrees East of North and
the compass itself would be pointing North.

Or, if the degrees are marked on the rotating disk instead of on the compass case, if
0 degrees is pointing at Magnetic North, then 344 degrees (360 - 16) is pointing
due North.

In your case your declination is probably the other direction - the compass needle will
point a bit to the left of true north on the East Coast.

The compasses that have adjustable declination settings rotate the base plate with
the arrow that you align the needle to.  You'd set that to +10 degrees so when the
needle is lined up it points a bit to the left of 0 degrees, which would then be true
North.  The details depend on the type of compass and how you are using it, but
you would hold the compass so that the needle is a bit to the left.

If you take a pure magnetic bearing it will be 10 degrees GREATER than the true
bearing on the East Coast, or 16 degrees LESS than true on the West Coast.
Logged
W8JX
Member

Posts: 5492




Ignore
« Reply #37 on: March 12, 2012, 04:12:13 PM »

So a dumb question about the declination figures.

If I'm looking at a compass and I'm pointing at true North, but declination for the area from NOAA is 10 degrees, does that mean +10 deg is true North or does it mean that 350 degrees is true north?

It wasn't particularly clear having nothing else to refer to.

East is least and West is best....  In a nut shell if you live east magnetic north you subtract declination from zero on compass face (counter to left of zero/North) and have needle point to this amount. If you live west of it you add the declination to zero and point needle to it.  When you do this the compass face will be pointing true north.  If you have a rotating face type compass you do opposite and when west subtract declination from north and use this point as true north. For east add to it for true north. 
Logged

--------------------------------------
Entered using a  WiFi Win 8.1 RT tablet or a Android tablet using 4G/LTE or WiFi.
K7KBN
Member

Posts: 2766




Ignore
« Reply #38 on: March 12, 2012, 04:22:44 PM »

"Can Dead Men Vote Twice"?

http://www.alisonosinski.com/?p=132
Logged

73
Pat K7KBN
CWO4 USNR Ret.
W1JKA
Member

Posts: 1619




Ignore
« Reply #39 on: March 12, 2012, 05:15:50 PM »

     Can Dead Men Vote Twice And Eat Too. Don't forget you variation,any navigator will explain it to you.
Logged
WF2S
Member

Posts: 12




Ignore
« Reply #40 on: March 26, 2012, 02:54:34 PM »

To top it all off, I found out that the adjustment or offset between True and Magnetic North  changes over time..  Just when I thought the yagis were calibrated correctly withthe rotor HI HI....Beamwidth of HF yagi antennas appears tobe very forgiving ...
Logged
VK5DO
Member

Posts: 79




Ignore
« Reply #41 on: March 26, 2012, 05:20:37 PM »

The first step is to find out what the actual magnetic variation is in your area.

Then.......

Magnetic to True North with easterly variation -  Add the variation to your magnetic bearing to get true north
True North to Magnetic with easterly variation - subtract the variation from your true north bearing to get magnetic north
Magnetic to True with westerly variariation - subtract the variation from magnetic to get true
True to magnetic with westerly variation - add the variation to your true to get magnetic

As sea you also take into account another factor called compass deviation but I wouldn't bother with that in your situation.

Mucking around with sticks in the ground etc might be an interesting excercise but I wouldn't bother when the above system has been working for navigators for hundreds of years and will give you an answer to the degree.

Dene

Logged
WB6BYU
Member

Posts: 13043




Ignore
« Reply #42 on: March 27, 2012, 08:10:06 AM »

Quote from: VK5DO

As sea you also take into account another factor called compass deviation but I wouldn't bother with that in your situation.



And certainly don't confuse them with the fact that an Australian compass is built
differently than a North American compass.
Logged
WA2ENM
Member

Posts: 3




Ignore
« Reply #43 on: March 27, 2012, 10:25:07 AM »

Fellows, this is more than you want to know, but maybe you can impress your friends at the next cocktail party.

VARIATION is the angular difference between true north and magnetic north at a given point on the earth. It's not the same everywhere and it changes! E.g., near me, the base variation in 2003 was 6 degrees, 15 minutes West, with "Annual increase of 7 minutes". So today I expect True North to be 7 degrees, 18 minutes West (I'll leave it to the curious to check my arithmetic). Get the variation baseline info for your area from a geodetic chart or, if you live near the shore, a marine chart.

DEVIATION is the error in a magnetic compass caused by local magnetic influences. E.g., that metal storage shed in your yard, etc. Deviation is East of West of magnetic north and it changes with your (think beam) heading. So you need to plot the Deviation at your antenna for the various headings. (a compass correction card).

COMPASS ERROR is the algebraic sum of Variation and Deviation.

DECLINATION is a measurement in Celestial Navigation and beyond the scope of this Thread.  I only mention it because someone had confused it with Variation.

Logged
PA9X
Member

Posts: 3




Ignore
« Reply #44 on: March 28, 2012, 01:51:41 PM »

Start up Google Maps in satellite mode, pick out a landmark (could also be a specific detail of your neighbours house) in southern or northern direction. Climb or lower your tower and point the beam to the specific landmark. Simple and accurate!

73

PA9X
Logged
Pages: Prev 1 2 [3] 4 Next   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.11 | SMF © 2006-2009, Simple Machines LLC Valid XHTML 1.0! Valid CSS!