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  #1   Report Post  
Kevin O'
 
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Default How to you point a roof antenna?

I don't know - BUT - wouldn't you install a motor to turn the antenna so it
could be adjusted to several signal sources?

K.



"New Question" wrote in message
...
Here is a standard roof antenna:
http://www.ktielectronics.com/channe...ge_antenna.htm

Which end of the antenna is supposed to be pointed in the direction of the
signal source? The left end (the end with the the longests elements) or

the
right end (the end with the shortest elements)?





  #2   Report Post  
Kevin O'
 
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Default How to you point a roof antenna?

I don't know - BUT - wouldn't you install a motor to turn the antenna so it
could be adjusted to several signal sources?

K.



"New Question" wrote in message
...
Here is a standard roof antenna:
http://www.ktielectronics.com/channe...ge_antenna.htm

Which end of the antenna is supposed to be pointed in the direction of the
signal source? The left end (the end with the the longests elements) or

the
right end (the end with the shortest elements)?





  #3   Report Post  
Dave Solly
 
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Default How to you point a roof antenna?

"New Question" wrote in
:

Here is a standard roof antenna:
http://www.ktielectronics.com/channe...ge_antenna.htm

Which end of the antenna is supposed to be pointed in the direction of
the signal source? The left end (the end with the the longests
elements) or the right end (the end with the shortest elements)?




Think of the end with the small elements and the "open mouth"of elements as
trying to eat the signal. In otherwords, the small elements point to the
signal source.
  #4   Report Post  
Dave Solly
 
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Default How to you point a roof antenna?

"New Question" wrote in
:

Here is a standard roof antenna:
http://www.ktielectronics.com/channe...ge_antenna.htm

Which end of the antenna is supposed to be pointed in the direction of
the signal source? The left end (the end with the the longests
elements) or the right end (the end with the shortest elements)?




Think of the end with the small elements and the "open mouth"of elements as
trying to eat the signal. In otherwords, the small elements point to the
signal source.
  #5   Report Post  
dicko
 
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Default How to you point a roof antenna?

On Fri, 15 Aug 2003 21:05:27 GMT, "Patch"
wrote:


"New Question" wrote in message
.. .
Here is a standard roof antenna:
http://www.ktielectronics.com/channe...ge_antenna.htm

Which end of the antenna is supposed to be pointed in the direction of the
signal source? The left end (the end with the the longests elements) or

the
right end (the end with the shortest elements)?


The short elements (UHF) goes to the front. Look at some of your neighbors

antennas to see what direction to aim it. You may have to fine tune it's
direction a bit.

If you go to www.antennaweb.org, it will give you compass bearings for
all the stations you can receive. Then it's a simple matter of getting
up on the roof with a compass and accurately pointing the antenna per
the compass.

dickm




  #6   Report Post  
dicko
 
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Default How to you point a roof antenna?

On Fri, 15 Aug 2003 21:05:27 GMT, "Patch"
wrote:


"New Question" wrote in message
.. .
Here is a standard roof antenna:
http://www.ktielectronics.com/channe...ge_antenna.htm

Which end of the antenna is supposed to be pointed in the direction of the
signal source? The left end (the end with the the longests elements) or

the
right end (the end with the shortest elements)?


The short elements (UHF) goes to the front. Look at some of your neighbors

antennas to see what direction to aim it. You may have to fine tune it's
direction a bit.

If you go to www.antennaweb.org, it will give you compass bearings for
all the stations you can receive. Then it's a simple matter of getting
up on the roof with a compass and accurately pointing the antenna per
the compass.

dickm


  #7   Report Post  
New Question
 
Posts: n/a
Default How to you point a roof antenna?

"dicko" wrote in message
...
If you go to www.antennaweb.org, it will give you compass bearings for
all the stations you can receive. Then it's a simple matter of getting
up on the roof with a compass and accurately pointing the antenna per
the compass.


Where can I purchase an inexpensive compass for doing this?

The compasses I've seen on the internet appear to indicate the following:

South: 0 degrees
West: 90 degrees
North: 180 degrees
East: 270 degrees

Is it possible to just look at my approximate location on a map and estimate
the correct direction to point the antenna in, based upon the direction of
the particular stations the I use the most?





  #8   Report Post  
New Question
 
Posts: n/a
Default How to you point a roof antenna?

"dicko" wrote in message
...
If you go to www.antennaweb.org, it will give you compass bearings for
all the stations you can receive. Then it's a simple matter of getting
up on the roof with a compass and accurately pointing the antenna per
the compass.


Where can I purchase an inexpensive compass for doing this?

The compasses I've seen on the internet appear to indicate the following:

South: 0 degrees
West: 90 degrees
North: 180 degrees
East: 270 degrees

Is it possible to just look at my approximate location on a map and estimate
the correct direction to point the antenna in, based upon the direction of
the particular stations the I use the most?





  #9   Report Post  
Joseph Meehan
 
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Default How to you point a roof antenna?

Frankly the idea of pointing the antenna towards the source signal, is
not the best real life solution. In real life the signal is often bounced
around so much that by the time it gets to you the best direction (strongest
signal and least amount of ghosting) may be much different.

I suggest taking a guess and then get back off the roof and check it
out. Then go back and try moving it. A few ups and downs and you should
have what works best for you. You neighbor may need a different direction.

Good Luck

--
Joseph E. Meehan

26 + 6 = 1 It's Irish Math


"New Question" wrote in message
...
Here is a standard roof antenna:
http://www.ktielectronics.com/channe...ge_antenna.htm

Which end of the antenna is supposed to be pointed in the direction of the
signal source? The left end (the end with the the longests elements) or

the
right end (the end with the shortest elements)?





  #10   Report Post  
Joseph Meehan
 
Posts: n/a
Default How to you point a roof antenna?

Frankly the idea of pointing the antenna towards the source signal, is
not the best real life solution. In real life the signal is often bounced
around so much that by the time it gets to you the best direction (strongest
signal and least amount of ghosting) may be much different.

I suggest taking a guess and then get back off the roof and check it
out. Then go back and try moving it. A few ups and downs and you should
have what works best for you. You neighbor may need a different direction.

Good Luck

--
Joseph E. Meehan

26 + 6 = 1 It's Irish Math


"New Question" wrote in message
...
Here is a standard roof antenna:
http://www.ktielectronics.com/channe...ge_antenna.htm

Which end of the antenna is supposed to be pointed in the direction of the
signal source? The left end (the end with the the longests elements) or

the
right end (the end with the shortest elements)?







  #11   Report Post  
meirman
 
Posts: n/a
Default How to you point a roof antenna?

In alt.home.repair on Fri, 15 Aug 2003 19:19:46 -0400 "Colbyt"
posted:


Where can I purchase an inexpensive compass for doing this?

The compasses I've seen on the internet appear to indicate the following:

South: 0 degrees
West: 90 degrees
North: 180 degrees
East: 270 degrees


That seems strange. Have you tried turning your monitor upside down.

Is it possible to just look at my approximate location on a map and

estimate
the correct direction to point the antenna in, based upon the direction of
the particular stations the I use the most?


I think that is a good start, although the transmitter is very often
not at the same location as the studio.

I think you want someone at the tv watching, with an intercom (finally
something to use the speakerphone on your cordlss phone for) who can
look at all the stations each time you move the antenna a bit, and
find the best compromise.

Maybe if you are in Kansas there is nothing to cause a ghost in any
station, but I think most places there are tall buildings (don't have
to be as tall as the transmitter, just think think of a triangle
within bigger triangle with the same angles, with one corner in the
same place.) that can cause ghosts. Turning the antenna a bit may get
rid of them, or cause other improvements.

I had a rotator on one of attic antennas, which I used for years, and
unless it was bad and could be made good, rotating seemed like a lot
of work each time I watched a different station. I ended up leaving
it in one place. Of course all my hard to get stations were in or
near DC, about 40 or 50 miles from my house, so they were all in
roughly the same direction.



I think I paid $2 for a 360 degree one at Wally World (Wal*Mart).


I agree. What could a cheap compass do? Point north but not quite
north?

If it only has a needle, where else could the magnet be? Maybe if it
a whole circle they could somehow assemble it wrong.

Anyhow you can verify it by gettting away from steel buildings,
determining which direction north is, and seeing what the compass
says. Even before you buy it, you can check them out. They have to
be separated, maybe a foot apart. But if 4 point in one direction and
1 points in another, don't buy the one.

You can do this before you buy a thermometer or an sand-filled egg
timer too.

Visit the site dicko posted, if you know your zip code you are done.



Meirman

If emailing, please let me know whether
or not you are posting the same letter.

Change domain to erols.com, if necessary.
  #12   Report Post  
meirman
 
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Default How to you point a roof antenna?

In alt.home.repair on Fri, 15 Aug 2003 19:19:46 -0400 "Colbyt"
posted:


Where can I purchase an inexpensive compass for doing this?

The compasses I've seen on the internet appear to indicate the following:

South: 0 degrees
West: 90 degrees
North: 180 degrees
East: 270 degrees


That seems strange. Have you tried turning your monitor upside down.

Is it possible to just look at my approximate location on a map and

estimate
the correct direction to point the antenna in, based upon the direction of
the particular stations the I use the most?


I think that is a good start, although the transmitter is very often
not at the same location as the studio.

I think you want someone at the tv watching, with an intercom (finally
something to use the speakerphone on your cordlss phone for) who can
look at all the stations each time you move the antenna a bit, and
find the best compromise.

Maybe if you are in Kansas there is nothing to cause a ghost in any
station, but I think most places there are tall buildings (don't have
to be as tall as the transmitter, just think think of a triangle
within bigger triangle with the same angles, with one corner in the
same place.) that can cause ghosts. Turning the antenna a bit may get
rid of them, or cause other improvements.

I had a rotator on one of attic antennas, which I used for years, and
unless it was bad and could be made good, rotating seemed like a lot
of work each time I watched a different station. I ended up leaving
it in one place. Of course all my hard to get stations were in or
near DC, about 40 or 50 miles from my house, so they were all in
roughly the same direction.



I think I paid $2 for a 360 degree one at Wally World (Wal*Mart).


I agree. What could a cheap compass do? Point north but not quite
north?

If it only has a needle, where else could the magnet be? Maybe if it
a whole circle they could somehow assemble it wrong.

Anyhow you can verify it by gettting away from steel buildings,
determining which direction north is, and seeing what the compass
says. Even before you buy it, you can check them out. They have to
be separated, maybe a foot apart. But if 4 point in one direction and
1 points in another, don't buy the one.

You can do this before you buy a thermometer or an sand-filled egg
timer too.

Visit the site dicko posted, if you know your zip code you are done.



Meirman

If emailing, please let me know whether
or not you are posting the same letter.

Change domain to erols.com, if necessary.
  #13   Report Post  
meirman
 
Posts: n/a
Default How to you point a roof antenna?

In alt.home.repair on Fri, 15 Aug 2003 16:16:11 -0500 dicko
posted:

On Fri, 15 Aug 2003 21:05:27 GMT, "Patch"
wrote:


"New Question" wrote in message
. ..
Here is a standard roof antenna:
http://www.ktielectronics.com/channe...ge_antenna.htm

Which end of the antenna is supposed to be pointed in the direction of the
signal source? The left end (the end with the the longests elements) or

the
right end (the end with the shortest elements)?


The short elements (UHF) goes to the front. Look at some of your neighbors

antennas to see what direction to aim it. You may have to fine tune it's
direction a bit.

If you go to www.antennaweb.org, it will give you compass bearings for
all the stations you can receive. Then it's a simple matter of getting
up on the roof with a compass and accurately pointing the antenna per
the compass.


This is great. You should probably give them your street address, or
you next door neighbor's ( ), it changed the reading for my local
stations by 18 degrees, and for the dc stations by 1 degree. And I'm
centrally located in my zipcode when looking towards DC, not so when
looking to my city.

BTW, the numbers used are standard, afaik. O is north, 90 is east,
etc.

This is interesting. To save the data, I selected it with the cursor
and copied it to an 80 column area, a new Eudora email. Every line
wrapped. The third time I used Cntl-A to highlight it all. None of
the lines wrapped. Much easier to read, no fiddling necessary.

dickm



Meirman

If emailing, please let me know whether
or not you are posting the same letter.

Change domain to erols.com, if necessary.
  #14   Report Post  
meirman
 
Posts: n/a
Default How to you point a roof antenna?

In alt.home.repair on Fri, 15 Aug 2003 16:16:11 -0500 dicko
posted:

On Fri, 15 Aug 2003 21:05:27 GMT, "Patch"
wrote:


"New Question" wrote in message
. ..
Here is a standard roof antenna:
http://www.ktielectronics.com/channe...ge_antenna.htm

Which end of the antenna is supposed to be pointed in the direction of the
signal source? The left end (the end with the the longests elements) or

the
right end (the end with the shortest elements)?


The short elements (UHF) goes to the front. Look at some of your neighbors

antennas to see what direction to aim it. You may have to fine tune it's
direction a bit.

If you go to www.antennaweb.org, it will give you compass bearings for
all the stations you can receive. Then it's a simple matter of getting
up on the roof with a compass and accurately pointing the antenna per
the compass.


This is great. You should probably give them your street address, or
you next door neighbor's ( ), it changed the reading for my local
stations by 18 degrees, and for the dc stations by 1 degree. And I'm
centrally located in my zipcode when looking towards DC, not so when
looking to my city.

BTW, the numbers used are standard, afaik. O is north, 90 is east,
etc.

This is interesting. To save the data, I selected it with the cursor
and copied it to an 80 column area, a new Eudora email. Every line
wrapped. The third time I used Cntl-A to highlight it all. None of
the lines wrapped. Much easier to read, no fiddling necessary.

dickm



Meirman

If emailing, please let me know whether
or not you are posting the same letter.

Change domain to erols.com, if necessary.
  #15   Report Post  
meirman
 
Posts: n/a
Default How to you point a roof antenna?

In alt.home.repair on Fri, 15 Aug 2003 17:30:49 -0400 "New Question"
posted:

"dicko" wrote in message
.. .
If you go to www.antennaweb.org, it will give you compass bearings for
all the stations you can receive. Then it's a simple matter of getting
up on the roof with a compass and accurately pointing the antenna per
the compass.


Where can I purchase an inexpensive compass for doing this?

The compasses I've seen on the internet appear to indicate the following:

South: 0 degrees
West: 90 degrees
North: 180 degrees
East: 270 degrees


I think this is because, when the numbers are written on the bottom of
the chamber and all that rotates is the needle, this would be wrong.

But when there is a disk that rotates, the labelling on the disk has
to be different from the labeling on the bottom of the chamber, or it
doesn't work. Anyhow, your numbers might work out on a compass with a
disk, but otherwise they are wrong.

Is it possible to just look at my approximate location on a map and estimate
the correct direction to point the antenna in, based upon the direction of
the particular stations the I use the most?






Meirman

If emailing, please let me know whether
or not you are posting the same letter.

Change domain to erols.com, if necessary.


  #16   Report Post  
meirman
 
Posts: n/a
Default How to you point a roof antenna?

In alt.home.repair on Fri, 15 Aug 2003 17:30:49 -0400 "New Question"
posted:

"dicko" wrote in message
.. .
If you go to www.antennaweb.org, it will give you compass bearings for
all the stations you can receive. Then it's a simple matter of getting
up on the roof with a compass and accurately pointing the antenna per
the compass.


Where can I purchase an inexpensive compass for doing this?

The compasses I've seen on the internet appear to indicate the following:

South: 0 degrees
West: 90 degrees
North: 180 degrees
East: 270 degrees


I think this is because, when the numbers are written on the bottom of
the chamber and all that rotates is the needle, this would be wrong.

But when there is a disk that rotates, the labelling on the disk has
to be different from the labeling on the bottom of the chamber, or it
doesn't work. Anyhow, your numbers might work out on a compass with a
disk, but otherwise they are wrong.

Is it possible to just look at my approximate location on a map and estimate
the correct direction to point the antenna in, based upon the direction of
the particular stations the I use the most?






Meirman

If emailing, please let me know whether
or not you are posting the same letter.

Change domain to erols.com, if necessary.
  #17   Report Post  
Banister Stairwell
 
Posts: n/a
Default How to you point a roof antenna?

"New Question" wrote in message
...
"dicko" wrote in message
...
If you go to www.antennaweb.org, it will give you compass bearings for
all the stations you can receive. Then it's a simple matter of getting
up on the roof with a compass and accurately pointing the antenna per
the compass.


Where can I purchase an inexpensive compass for doing this?

The compasses I've seen on the internet appear to indicate the following:

South: 0 degrees
West: 90 degrees
North: 180 degrees
East: 270 degrees


This is opposite to what it should be. A heading of North is 360 degrees,
South is 180 degrees, East is 090 degrees and West is 270 degrees.

Is it possible to just look at my approximate location on a map and

estimate
the correct direction to point the antenna in, based upon the direction of
the particular stations the I use the most?


Keep in mind, the directions given on the www.antennaweb.org website are
based on *magnetic* north, not true north. It assumes that you will be
using a magnetic compass to point your antenna.

If you use a map to determine relative direction to the station, it will be
based on *true* north, not magnetic north. Depending on where you live,
there can be as much as 20 degrees difference between true and magnetic
north. If you figure the direction to the station on the map, and then use
the compass on the roof to figure relative direction based on what you came
up with on the map, you could be as much as 20 degrees off (depending on
where in the USA you live). This is because the geographic poles and the
magnetic poles are not collocated. Plus, stray magnetic fields in the earth
introduce some error as well. It's called magnetic variation. It's easy to
compensate for if you know what the variation is in your particular
geographic area. For example, if the magnetic variation is roughly 15
degrees east, and you calculate the relative direction to the station on the
map as due West (270 degrees), you would need to subtract 15 degrees from
your compass reading and point the antenna to 255 degrees magnetic.


  #18   Report Post  
Banister Stairwell
 
Posts: n/a
Default How to you point a roof antenna?

"New Question" wrote in message
...
"dicko" wrote in message
...
If you go to www.antennaweb.org, it will give you compass bearings for
all the stations you can receive. Then it's a simple matter of getting
up on the roof with a compass and accurately pointing the antenna per
the compass.


Where can I purchase an inexpensive compass for doing this?

The compasses I've seen on the internet appear to indicate the following:

South: 0 degrees
West: 90 degrees
North: 180 degrees
East: 270 degrees


This is opposite to what it should be. A heading of North is 360 degrees,
South is 180 degrees, East is 090 degrees and West is 270 degrees.

Is it possible to just look at my approximate location on a map and

estimate
the correct direction to point the antenna in, based upon the direction of
the particular stations the I use the most?


Keep in mind, the directions given on the www.antennaweb.org website are
based on *magnetic* north, not true north. It assumes that you will be
using a magnetic compass to point your antenna.

If you use a map to determine relative direction to the station, it will be
based on *true* north, not magnetic north. Depending on where you live,
there can be as much as 20 degrees difference between true and magnetic
north. If you figure the direction to the station on the map, and then use
the compass on the roof to figure relative direction based on what you came
up with on the map, you could be as much as 20 degrees off (depending on
where in the USA you live). This is because the geographic poles and the
magnetic poles are not collocated. Plus, stray magnetic fields in the earth
introduce some error as well. It's called magnetic variation. It's easy to
compensate for if you know what the variation is in your particular
geographic area. For example, if the magnetic variation is roughly 15
degrees east, and you calculate the relative direction to the station on the
map as due West (270 degrees), you would need to subtract 15 degrees from
your compass reading and point the antenna to 255 degrees magnetic.


  #19   Report Post  
stork
 
Posts: n/a
Default How to you point a roof antenna?


wrote in message
...
On Fri, 15 Aug 2003 20:57:09 GMT, "Kevin O'"


wrote:

I don't know - BUT - wouldn't you install a motor to turn the antenna so

it
could be adjusted to several signal sources?


That would really depend on where you are located. For many people, there

is
little or no advantage to a rotator.


My folks live in New Jersey between New York and Philadelphia. The antenna
with rotor worked ok for one TV, but if more than one (split to the same
antenna) was in use, there was a problem if all parties didn't agree on the
broadcast city! Their fix was to eliminate the rotor and mount two
antennas, one pointing towards the NYC towers and the other towards the
Philly stations. These were both split and cabled to each TV, where they
have been attached with an a/b box. Where useful, the a/b box has a remote.

AStork


---
Outgoing mail is certified Virus Free.
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  #20   Report Post  
stork
 
Posts: n/a
Default How to you point a roof antenna?


wrote in message
...
On Fri, 15 Aug 2003 20:57:09 GMT, "Kevin O'"


wrote:

I don't know - BUT - wouldn't you install a motor to turn the antenna so

it
could be adjusted to several signal sources?


That would really depend on where you are located. For many people, there

is
little or no advantage to a rotator.


My folks live in New Jersey between New York and Philadelphia. The antenna
with rotor worked ok for one TV, but if more than one (split to the same
antenna) was in use, there was a problem if all parties didn't agree on the
broadcast city! Their fix was to eliminate the rotor and mount two
antennas, one pointing towards the NYC towers and the other towards the
Philly stations. These were both split and cabled to each TV, where they
have been attached with an a/b box. Where useful, the a/b box has a remote.

AStork


---
Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.510 / Virus Database: 307 - Release Date: 8/15/03



  #21   Report Post  
CMF
 
Posts: n/a
Default How to you point a roof antenna?


wrote in message
...
On Sat, 16 Aug 2003 04:49:45 GMT, "Banister Stairwell"
wrote:

Keep in mind, the directions given on the www.antennaweb.org website are
based on *magnetic* north, not true north. It assumes that you will be
using a magnetic compass to point your antenna.


What the heck are you talking about? North is North. Why would a
compass point different?

Actually, the magnetic north pole, so to speak is not exactly up where Santa
lives. And, something I just learned by a fast web search, it is moving.
Check out this article. http://www.cnn.com/2002/TECH/space/03/20/north.pole/

So, unless you are on the exact line of longitude that the magnetic pole
happens to be on, then you would get a false 'true north' reading.

Maury


  #22   Report Post  
CMF
 
Posts: n/a
Default How to you point a roof antenna?


wrote in message
...
On Sat, 16 Aug 2003 04:49:45 GMT, "Banister Stairwell"
wrote:

Keep in mind, the directions given on the www.antennaweb.org website are
based on *magnetic* north, not true north. It assumes that you will be
using a magnetic compass to point your antenna.


What the heck are you talking about? North is North. Why would a
compass point different?

Actually, the magnetic north pole, so to speak is not exactly up where Santa
lives. And, something I just learned by a fast web search, it is moving.
Check out this article. http://www.cnn.com/2002/TECH/space/03/20/north.pole/

So, unless you are on the exact line of longitude that the magnetic pole
happens to be on, then you would get a false 'true north' reading.

Maury


  #23   Report Post  
Terry
 
Posts: n/a
Default How to you point a roof antenna?

wrote:

What the heck are you talking about? North is North. Why would a
compass point different?


Not so:
To explain.
The instructions that came with our satellite system first asked
our location. It then referred us to a table of MAGNETIC compass
bearings for different locations across the country. (We are
about as far east in North America as one can get only 1600 miles
fom the coast of Ireland!) so, in our case, the satellite/s are
to the west of us, generally over the middle of the North
American continent and are therefore, to us, at a fairly low
angle of elevation.
The table of magnetic bearings took into account magnetic
deviations for year 2002 because the earth's magnetic north and
south poles also move around a bit. I understand the magnetic
north pole is in the western Canadian Arctic. The annual
change/deviation in degrees is small; often shown on the edge of
topographical maps.
There are places of course where the north magnetic pole and the
actual geographic north pole might be sort of 'in line' to your
location and people there wouldn't have to worry too much about
the difference. That would probably be in extreme west of the
United States or Canada?
About 55 years ago I lived in Europe and IIRC the difference
between magnetic and geographic north was about 15 degrees, west.
Initially with our satellite dish we had more trouble getting the
elevation than the magnetic bearing. The mounting bracket
elevation markings did not match the instructions. When the dish
supplied with the bracket was mounted on it what looked like zero
elevation was actually about +22 degrees to horizontal. We
eventually figured it out and service has been good. We presumed
that the supplier had changed the type of dish or the bracket
since the instructions were printed.
I just checked on "North Magnetic" and it advises that the North
'Magnetic' Pole is in the Canadian Arctic and, at the moment, is
moving northwest by an average of about 25 miles per year. It's
at a latitude of about 80 degrees north; about 20 degrees south
of the Geographic North pole! In the year 1831 it was at 70
degrees north, even further south. One estimate is that if it
keeps moving at present rate it will, in about 50 years, be in
Siberia.
It can also move daily due to disturbances in the earths magnetic
field by as much as 50 miles, between noon and midnight!
Radiation from the sun is one factor affecting the earth's
magnetic field. BTW. The South 'Magnetic' Pole is south of
Australia on the coast of Antarctica.
Interesting when something triggers you to check on something;
thanks for the question.
Terry.
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Terry
 
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Default How to you point a roof antenna?

wrote:

What the heck are you talking about? North is North. Why would a
compass point different?


Not so:
To explain.
The instructions that came with our satellite system first asked
our location. It then referred us to a table of MAGNETIC compass
bearings for different locations across the country. (We are
about as far east in North America as one can get only 1600 miles
fom the coast of Ireland!) so, in our case, the satellite/s are
to the west of us, generally over the middle of the North
American continent and are therefore, to us, at a fairly low
angle of elevation.
The table of magnetic bearings took into account magnetic
deviations for year 2002 because the earth's magnetic north and
south poles also move around a bit. I understand the magnetic
north pole is in the western Canadian Arctic. The annual
change/deviation in degrees is small; often shown on the edge of
topographical maps.
There are places of course where the north magnetic pole and the
actual geographic north pole might be sort of 'in line' to your
location and people there wouldn't have to worry too much about
the difference. That would probably be in extreme west of the
United States or Canada?
About 55 years ago I lived in Europe and IIRC the difference
between magnetic and geographic north was about 15 degrees, west.
Initially with our satellite dish we had more trouble getting the
elevation than the magnetic bearing. The mounting bracket
elevation markings did not match the instructions. When the dish
supplied with the bracket was mounted on it what looked like zero
elevation was actually about +22 degrees to horizontal. We
eventually figured it out and service has been good. We presumed
that the supplier had changed the type of dish or the bracket
since the instructions were printed.
I just checked on "North Magnetic" and it advises that the North
'Magnetic' Pole is in the Canadian Arctic and, at the moment, is
moving northwest by an average of about 25 miles per year. It's
at a latitude of about 80 degrees north; about 20 degrees south
of the Geographic North pole! In the year 1831 it was at 70
degrees north, even further south. One estimate is that if it
keeps moving at present rate it will, in about 50 years, be in
Siberia.
It can also move daily due to disturbances in the earths magnetic
field by as much as 50 miles, between noon and midnight!
Radiation from the sun is one factor affecting the earth's
magnetic field. BTW. The South 'Magnetic' Pole is south of
Australia on the coast of Antarctica.
Interesting when something triggers you to check on something;
thanks for the question.
Terry.
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