How to calibrate the azimuth angle?
Dear all,
I am Chiu-Teng Tsai (BM6ERA) from Taiwan. Now we are building a mobile ground station. One of our problem is how to calibrate the azimuth angle. Use compass only, or any better solution? Thanks for your help!
Best regards,
Chiu-Teng Tsai
At 04:08 PM 12/27/2007, Chiu-Teng Tsai wrote:
Dear all,
I am Chiu-Teng Tsai (BM6ERA) from Taiwan. Now we are building amobile ground station. One of our problem is how to calibrate the azimuth angle. Use compass only, or any better solution? Thanks for your help!
Azimuth is given in degrees from true North. A compass is fine, if you know the magnetic declination (i.e. the difference between true North and magnetic North) for your location. That information should be readily available on the Internet.
73 de VK3JED http://vkradio.com
You could be interested to have a look at http://www.vhfdx.net/discuss/truenorth.html
73. Gabriel - EA6VQ ======================================================================= Web-Site: HTTP://www.vhfdx.net VQLog: HTTP://www.vqlog.com VHF-UHF Propagation ticker: HTTP://www.vhfdx.net/spots/map.php?Frec=TIC =======================================================================
-----Mensaje original----- De: [email protected] [mailto:[email protected]]En nombre de Tony Langdon Enviado el: jueves, 27 de diciembre de 2007 9:30 Para: Chiu-Teng Tsai; [email protected] Asunto: [amsat-bb] Re: How to calibrate the azimuth angle?
At 04:08 PM 12/27/2007, Chiu-Teng Tsai wrote:
Dear all,
I am Chiu-Teng Tsai (BM6ERA) from Taiwan. Now we are building amobile ground station. One of our problem is how to calibrate the azimuth angle. Use compass only, or any better solution? Thanks
for your help!
Azimuth is given in degrees from true North. A compass is fine, if you know the magnetic declination (i.e. the difference between true North and magnetic North) for your location. That information should be readily available on the Internet.
73 de VK3JED http://vkradio.com
Sent via [email protected]. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
----- Original Message ----- From: "Tony Langdon" [email protected] To: "Chiu-Teng Tsai" [email protected]; [email protected] Sent: Thursday, December 27, 2007 3:30 AM Subject: [amsat-bb] Re: How to calibrate the azimuth angle?
At 04:08 PM 12/27/2007, Chiu-Teng Tsai wrote:
Dear all,
I am Chiu-Teng Tsai (BM6ERA) from Taiwan. Now we are building amobile ground station. One of our problem is how to calibrate the azimuth angle. Use compass only, or any better solution? Thanks for your help!
Azimuth is given in degrees from true North. A compass is fine, if you know the magnetic declination (i.e. the difference between true North and magnetic North) for your location. That information should be readily available on the Internet.
73 de VK3JED http://vkradio.com
If the declination is less than half of your antenna's 3 dB beamwidth, you can probably ignore it and just point to magnetic north. With a dish, it becomes significant, however.
Another tried and true method is to track the sun, and adjust your antenna mounts and rotor mount to cast the smallest shadow ("X") of your antennas on the ground, or sight thru the antenna boom ("boresight") while tracking the moon (DON'T look at the sun!).
George, KA3HSW
It is easy to calibrate an azimuth scale any time the Sun is available, see attached.
John WA4WDL
----- Original Message ----- From: "Chiu-Teng Tsai" [email protected] To: [email protected] Sent: Thursday, December 27, 2007 12:08 AM Subject: [amsat-bb] How to calibrate the azimuth angle?
Dear all,
I am Chiu-Teng Tsai (BM6ERA) from Taiwan. Now we are building a mobile ground station. One of our problem is how to calibrate the azimuth angle. Use compass only, or any better solution? Thanks for your help!
Best regards,
Chiu-Teng Tsai _______________________________________________ Sent via [email protected]. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
Hi all...
This works for AZ and EL
Want to know where the Sun is if your tracking software doesn't include the Sun? Run the free SPC
http://web.ift.uib.no/~neda/suncalc/spc.html
Track the Sun manually with your antenna controller or through your software. Note the shadow on the ground that the antennae produce. Crossed yagi will show a "X" when the antenna is properly pointed. If the antenna is too far from the ground or you cannot place anything near the back end of the beam to see the shadow use plan B. Caution! Sight the sun along the antenna beam using welding glasses to see that it is pointing at the sun. You can also try the "pin hole camera" trick to project the sun's image and antenna shadow onto another surface as you do when watching Sun spots.
http://solar-center.stanford.edu/observe/
Mechanically adjust AZ/EL at the antenna to point at the Sun while the rotator controller logically tracks the Sun.
Advantage of these methods is that it doesn't matter what time of day you are mechanically tweaking your antenna and you can take your time loosening and tightening bolts on AZ and EL.
73, Alan VE4YZ
-----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Chiu-Teng Tsai Sent: December 26, 2007 11:08 PM To: [email protected] Subject: [amsat-bb] How to calibrate the azimuth angle?
Dear all,
I am Chiu-Teng Tsai (BM6ERA) from Taiwan. Now we are building a mobile ground station. One of our problem is how to calibrate the azimuth angle. Use compass only, or any better solution? Thanks for your help!
Best regards,
Chiu-Teng Tsai _______________________________________________ Sent via [email protected]. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
I am Chiu-Teng Tsai (BM6ERA) from Taiwan. Now we are building amobile ground station. One of our problem is how to calibrate the azimuth angle. Use compass only, or any better solution? Thanks for your help!
Chiu-Teng Tsai
That will certainly work. Use the North Star to calibrate your compass for deviation and variation at that location....Or the sun during the day.
Put a vertical 4' stick in the ground, and when its shadow is the shortest it is pointing to true north.
Moss on the side of a tree (south in your location) works, but not very accurate!!!
73, Dave, WB6LLO [email protected]
Disagree: I learn....
Pulling for P3E...
I am Chiu-Teng Tsai (BM6ERA) from Taiwan. Now we are building amobile ground station. One of our problem is how to calibrate the azimuth angle. Use compass only, or any better solution? Thanks for your help!
Chiu-Teng Tsai,
I forgot to tell you my old "crutch" to remember
True Variation Magnetic Deviation Compass
Two Virgins Make Dead Company add west..
Going the other way, subtract west...
73, Dave, WB6LLO [email protected]
Disagree: I learn....
Pulling for P3E...
At 09:08 PM 12/26/2007, Chiu-Teng Tsai wrote:
I am Chiu-Teng Tsai (BM6ERA) from Taiwan. Now we are building a mobile ground station. One of our problem is how to calibrate the azimuth angle. Use compass only, or any better solution? Thanks for your help!
I agree with the comments of others re two methods that work well: The stick in the ground, and tracking the sun.
Compasses are very difficult to use to get an accurate direction. First there's the issue of magnetic declination or magnetic variation, caused by the fact that the magnetic north pole is not at the north pole. You look up a number on a map or something, but most people frankly can't remember whether you're supposed to add the number or subtract it. This is a mess. But that's not all. Local iron (nearby cars, pipes in your house, or even the mast of your antennas can affect the reading more than you might imagine. (This is called magnetic deviation.) Sure, mariners have been using compasses for a zillion years, but they've studied variation and deviation, and calibrated their compasses for the magnetic effects on their boats, and have done it routinely over many years to keep themselves reminded of the details. The weekend antenna putter-upper has not. (With the advent of GPS etc, fewer and fewer mariners every day know how to use a compass.) Compasses on boats are nailed down, so that it is possible to calibrate out the effects of other (also nailed down) metal. When you're walking around with a compass, you don't have this luxury. I once tried to use a compass on an outing to figure out where to point an antenna, and as I walked around I kept getting different readings. Finally I realized that if I was anywhere near my car, the compass pointed toward my car. With a handheld compass you just have to stay far away from cars, houses, antenna masts, etc. You can't hold it in your left hand as you hang on the side of the steel tower tightening the rotor bolts, and expect success. With enough care, a compass can work, but getting an accurate reading is more difficult than most people presume.
I say just say no to compasses. Use the stick in the ground or tracking software that can point your antenna at the sun.
I suggest you start with the stick. That will give you enough info to assemble the system, tighten down the bolts, etc.
Pointing the antenna at the sun is the best final check, because it double checks so many pieces of your system. If you put the stick in the ground, that may make you know which way is North, but it doesn't mean you tightened down the screws with the mast in the right position, or calibrated the rotor control software right, or have the right timezone in your computer, etc.
With a Yagi antenna, because it is long and skinny, its shadow is a really accurate indication.
Franklin Antonio wrote: ...
Compasses are very difficult to use to get an accurate direction.
I've always had excellent results with a Brunton compass. It takes a few minutes to learn how to use one but it's well worth it.
http://en.wikipedia.org/wiki/Brunton_compass
Ollie, AJ1O
All: I have to agree with Franklin . .. . compasses are HARD. Starting with, it's difficult to get accurate variation & deviation information (delta between local magnetic & true North) for land-based locations.
Mariners, for centuries, used a now obsolete method of navigation called "celestial" -- which meant using sun, moon, stars, tables, and calculations to determine location based on observations.
One of those techniques was known (at least 35 years ago, when I first studied celestial Nav) as "Local apparent Noon". You started with an estimate of your latitude, determined a time offset from the center of the time zone based on assumed (dead-reckoning) position, and then started some time PRIOR. Using a sextant, you would start "swinging" the sun, and click a stopwatch (synchronized to WWV) at the highest elevation of sun. You have now determined the time when the sun's elevation is highest, or Local Apparent Noon. From that, you could determine longitude, and latitude using other techniques.
This process lends itself nicely to reverse engineering as follows: 1. Using your handy GPS, determine the most precise coordinates for your tower/antenna. 2. Synchronize your laptop or computer clock with any of the internet time servers. 3. Synchronize your watch with the laptop/computer. 4. Enter the pre-determined coordinates into your favorite tracking program (InstantTrack, Nova, SATPC32 . . . .) 5. Using the "fast forward" feature of that tracking program, move until you get sun azimuth of 180 degrees. This should coincide with maximum elevation. 6. Write down the time of max elevation/180 degree azimuth. 7. Stand "north" of your tower/antenna at about that time, with a stick or other marker. 8. When your watch indicates the appointed time, put the stick in the ground at the far extent of the shadow from your antenna/tower. 9. You just marked true North at your location.
Obviously the taller your antenna, and longer your shadow, the more accurate your marking will be. For any reasonable antenna height, this will be well within the accuracy of any reasonable amateur antenna system.
I have done this, and it matched PRECISELY with the direction determined using (difficult to determine) local variation and deviation vs. magnetic. I had the luxury of an open field, so suspect very little interference to the magnetic compass from "local" effects.
Frankly, I find the celestial method easier, and more repeatable, particularly at Field Day sites, etc.
Good luck & 73, Jim [email protected]
Ollie Eisman wrote:
Franklin Antonio wrote: ...
Compasses are very difficult to use to get an accurate direction.
I've always had excellent results with a Brunton compass. It takes a few minutes to learn how to use one but it's well worth it.
http://en.wikipedia.org/wiki/Brunton_compass
Ollie, AJ1O _______________________________________________ Sent via [email protected]. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
A compass won't give you accurate azimuth unless you know for sure that you're not near any large masses of metal, and even then, you will need to know your local magnetic deviation. I tried to use a compass to align a satellite dish once, and it put me so far off on the azimuth I never did find the satellite that way, even taking magnetic deviation into account. You might have better luck where you are, but it's a lot of work to do it that way even if it does work.
A much easier solution is to look at your location in Google Earth and find the orientation of a nearby road, and use that as your azimuth reference. That automatically gets you azimuth relative to true north, which makes the job considerably simpler. If you don't have nearby roads that are straight enough to be useful, find a distant visible landmark (like a radio tower) and determine what its azimuth is from your location, then use it as a reference point and find your desired azimuth from there. (A long time ago, I worked out a formula for determining the bearing to a distant landmark using only the latitude and longitude of it and the observing location. It's on paper somewhere, unfortunately I don't know where and I'd have to redo the math at this point. But if you're interested, let me know. It's not too difficult to measure the orientation of the baseline between the two using Google Earth though ..)
On Dec 26, 2007, at 11:08 PM, Chiu-Teng Tsai wrote:
Dear all,
I am Chiu-Teng Tsai (BM6ERA) from Taiwan. Now we are building a mobile ground station. One of our problem is how to calibrate the azimuth angle. Use compass only, or any better solution? Thanks for your help!
Best regards,
Chiu-Teng Tsai
"On this one we'd like to think of ourselves collectively as 'da men', sir." -- Toby Ziegler
Well, now that everyone has trashed compasses. Here's the compass that I really really like:
Click on "precision instruments", it's the Suunto Tandem. It's a compass and clinometer in a nice machined aluminum package. It has optical sites for both instruments that really improves accuracy (if you ask me). It's really well made and it's from Finland... If nothing else, you can walk around measuring the height of trees.
jeff
Bruce Bostwick wrote:
A compass won't give you accurate azimuth unless you know for sure that you're not near any large masses of metal, and even then, you will need to know your local magnetic deviation. I tried to use a compass to align a satellite dish once, and it put me so far off on the azimuth I never did find the satellite that way, even taking magnetic deviation into account. You might have better luck where you are, but it's a lot of work to do it that way even if it does work.
A much easier solution is to look at your location in Google Earth and find the orientation of a nearby road, and use that as your azimuth reference. That automatically gets you azimuth relative to true north, which makes the job considerably simpler. If you don't have nearby roads that are straight enough to be useful, find a distant visible landmark (like a radio tower) and determine what its azimuth is from your location, then use it as a reference point and find your desired azimuth from there. (A long time ago, I worked out a formula for determining the bearing to a distant landmark using only the latitude and longitude of it and the observing location. It's on paper somewhere, unfortunately I don't know where and I'd have to redo the math at this point. But if you're interested, let me know. It's not too difficult to measure the orientation of the baseline between the two using Google Earth though ..)
On Dec 26, 2007, at 11:08 PM, Chiu-Teng Tsai wrote:
Dear all,
I am Chiu-Teng Tsai (BM6ERA) from Taiwan. Now we are building a mobile ground station. One of our problem is how to calibrate the azimuth angle. Use compass only, or any better solution? Thanks for your help!
Best regards,
Chiu-Teng Tsai
"On this one we'd like to think of ourselves collectively as 'da men', sir." -- Toby Ziegler
Sent via [email protected]. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
Nobody's mentioned this one yet... Take any GPS receiver, put it at the base of your antenna structure, and note the co-ordinates. Then walk away from the first spot and, use the display, find another spot nearby like a wall, or just the ground that is exactly north of where you started. Place a marker on that spot like a stake, or target icon, and maybe paint a line connecting the two points on your ground. DONE!
'73 Auke
On Dec 26, 2007, at 11:08 PM, Chiu-Teng Tsai wrote:
Dear all,
I am Chiu-Teng Tsai (BM6ERA) from Taiwan. Now we are building a mobile ground station. One of our problem is how to calibrate the azimuth angle. Use compass only, or any better solution? Thanks for your help!
Best regards,
Chiu-Teng Tsai
"On this one we'd like to think of ourselves collectively as 'da men', sir." -- Toby Ziegler
Sent via [email protected]. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
Sent via [email protected]. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
-- No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.5.516 / Virus Database: 269.17.11/1200 - Release Date: 12/27/2007 1:34 PM
I don't know if the old Columbus trick works in the southern hemisphere but here i calibrate my antennas on Ursa Major AKA The north star.
Just place yourself just under your tower or your beam supporting structure locate the north star and pointed your antenna.
For those who are not able to see the north star too bad take a GPS i check with mine against the north star and its closed enough just make sure you are programming to see the thru north not the magnetic north.
"Is it true that water flush in reverse side in drain if you are in the southern hemisphere? an old non believer saying!
Luc Leblanc VE2DWE Skype VE2DWE www.qsl.net/ve2dwe WAC BASIC CW PHONE SATELLITE
All -
For what it's worth, Polaris' declination is 89.2 degrees. Consequently, it can be as much as 0.8 degrees "off" from true North.
For aligning an antenna whose beamwidth is 15-30 degrees, this error is trivial of course.
W9IP
Luc Leblanc wrote:
I don't know if the old Columbus trick works in the southern hemisphere but here i calibrate my antennas on Ursa Major AKA The north star.
Just place yourself just under your tower or your beam supporting structure locate the north star and pointed your antenna.
For those who are not able to see the north star too bad take a GPS i check with mine against the north star and its closed enough just make sure you are programming to see the thru north not the magnetic north.
"Is it true that water flush in reverse side in drain if you are in the southern hemisphere? an old non believer saying!
Luc Leblanc VE2DWE Skype VE2DWE www.qsl.net/ve2dwe WAC BASIC CW PHONE SATELLITE
Sent via [email protected]. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
I was just going to say that Polaris is close to the north celestial pole but not quite exactly on it, and if you're absolutely insanely obsessed with accuracy, you probably want to take two shots on it 180 degrees apart (12 hours apart in winter, if your latitude is high enough that you can fit two observations 12 hours apart into one night, or the same time on two nights 6 months apart, or whatever), and split the difference. If you're aiming at satellites, an error of less than a degree isn't going to matter much, though .. your antenna's main lobe is almost certainly wider than that. :)
On Dec 28, 2007, at 10:49 AM, Michael R. Owen wrote:
All -
For what it's worth, Polaris' declination is 89.2 degrees. Consequently, it can be as much as 0.8 degrees "off" from true North.
For aligning an antenna whose beamwidth is 15-30 degrees, this error is trivial of course.
W9IP
Luc Leblanc wrote:
I don't know if the old Columbus trick works in the southern hemisphere but here i calibrate my antennas on Ursa Major AKA The north star.
Just place yourself just under your tower or your beam supporting structure locate the north star and pointed your antenna.
For those who are not able to see the north star too bad take a GPS i check with mine against the north star and its closed enough just make sure you are programming to see the thru north not the magnetic north.
"Is it true that water flush in reverse side in drain if you are in the southern hemisphere? an old non believer saying!
Luc Leblanc VE2DWE Skype VE2DWE www.qsl.net/ve2dwe WAC BASIC CW PHONE SATELLITE
ENGLISH: A language that lurks in dark alleys, beats up other languages, and rifles through their pockets for spare vocabulary.
Thank's for those who correct me The north star is in Ursa minor constellation (not major) and for the half a degree or one error from the real north pole but as stated we can live with it and i should wrote also to be able to confirm the north with a GPS you should move away from your point towards Polaris this way your GPS will show you a direction pointing to the star.
As my main topic was about not loosing the north... that's the minimum i can wished you all in 2008. I am not too sure if wishing an Happy New Year is still relevant? Should we wished us all a better new year instead? In french we wished us good and happy new year (freely translated) a bit more realistic but lets say the goals are the same only the means differs.
Here is some help to understand the North Star.
Today the Earth's axis points within one degree of Polaris, the brightest star in the constellation Ursa Minor (also called the Little Bear or the Little Dipper). Polaris appears to be in a fixed position in the sky throughout the year. All other stars and constellations seem to revolve around the North Star.
In the case of the earth, precession is caused by the gravitational pull of the sun and the moon. The earth's axis makes one complete rotation over the course of approximately 26,000 years. If you trace the path of the axis in the sky, you will find that Polaris, Vega, Thuban, and Alpha Cephei all fall on or very close to it. So when the earth's axis is at a point on the path near Vega, Vega becomes the North Star while Thuban is the North Star when the axis is near it on the path.
Five thousand years ago, Thuban was the North Star. Five thousand years from now, the North Star will be Alpha Cephei. Seven thousand years after that, it will be Vega. Nine thousand years after that, Thuban will be the North Star again. At these dates, the various stars will be at the closest to absolute north. For some time before, the relevant star will be approaching due north and it will be receding for some time after the time listed. In these interim times, the North Star is whichever star is closest to north.
"-" P.S. The North pole cap is melting too...just a reminder when you will give your new year wishes! As i said don't loose the North ;)
Luc Leblanc VE2DWE Skype VE2DWE www.qsl.net/ve2dwe WAC BASIC CW PHONE SATELLITE
For those that want to actual;ly find it here is a cool page with an actual photo of the area of sky. and when you place your mouse over the words mouseover it gives you guide lines too,
http://www.astropix.com/HTML/C_SPRING/URSAS.HTM
or here is another simpler one http://www.physics.ucla.edu/~huffman/finddip.html
Joe WB9SBD
Luc Leblanc wrote:
Thank's for those who correct me The north star is in Ursa minor constellation (not major) and for the half a degree or one error from the real north pole but as stated we can live with it and i should wrote also to be able to confirm the north with a GPS you should move away from your point towards Polaris this way your GPS will show you a direction pointing to the star.
As my main topic was about not loosing the north... that's the minimum i can wished you all in 2008. I am not too sure if wishing an Happy New Year is still relevant? Should we wished us all a better new year instead? In french we wished us good and happy new year (freely translated) a bit more realistic but lets say the goals are the same only the means differs.
Here is some help to understand the North Star.
Today the Earth's axis points within one degree of Polaris, the brightest star in the constellation Ursa Minor (also called the Little Bear or the Little Dipper). Polaris appears to be in a fixed position in the sky throughout the year. All other stars and constellations seem to revolve around the North Star.
In the case of the earth, precession is caused by the gravitational pull of the sun and the moon. The earth's axis makes one complete rotation over the course of approximately 26,000 years. If you trace the path of the axis in the sky, you will find that Polaris, Vega, Thuban, and Alpha Cephei all fall on or very close to it. So when the earth's axis is at a point on the path near Vega, Vega becomes the North Star while Thuban is the North Star when the axis is near it on the path.
Five thousand years ago, Thuban was the North Star. Five thousand years from now, the North Star will be Alpha Cephei. Seven thousand years after that, it will be Vega. Nine thousand years after that, Thuban will be the North Star again. At these dates, the various stars will be at the closest to absolute north. For some time before, the relevant star will be approaching due north and it will be receding for some time after the time listed. In these interim times, the North Star is whichever star is closest to north.
"-" P.S. The North pole cap is melting too...just a reminder when you will give your new year wishes! As i said don't loose the North ;)
Luc Leblanc VE2DWE Skype VE2DWE www.qsl.net/ve2dwe WAC BASIC CW PHONE SATELLITE
Sent via [email protected]. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
Not meaning to trash compasses, just have had some less than satisfying experiences using them to align antennas on satellites due to the number of sources of measurement errors that have to be accounted for. I've used some very good compasses (my favorites are the ones from Morin that allow sighting across the compass to get a magnetic bearing of a landmark on the horizon :) but getting accurate true north out of even a good magnetic compass is a lot of work ..
On Dec 27, 2007, at 7:15 PM, Jeff Mock wrote:
Well, now that everyone has trashed compasses. Here's the compass that I really really like:
Click on "precision instruments", it's the Suunto Tandem. It's a compass and clinometer in a nice machined aluminum package. It has optical sites for both instruments that really improves accuracy (if you ask me). It's really well made and it's from Finland... If nothing else, you can walk around measuring the height of trees.
jeff
Bruce Bostwick wrote:
A compass won't give you accurate azimuth unless you know for sure that you're not near any large masses of metal, and even then, you will need to know your local magnetic deviation. I tried to use a compass to align a satellite dish once, and it put me so far off on the azimuth I never did find the satellite that way, even taking magnetic deviation into account. You might have better luck where you are, but it's a lot of work to do it that way even if it does work.
A much easier solution is to look at your location in Google Earth and find the orientation of a nearby road, and use that as your azimuth reference. That automatically gets you azimuth relative to true north, which makes the job considerably simpler. If you don't have nearby roads that are straight enough to be useful, find a distant visible landmark (like a radio tower) and determine what its azimuth is from your location, then use it as a reference point and find your desired azimuth from there. (A long time ago, I worked out a formula for determining the bearing to a distant landmark using only the latitude and longitude of it and the observing location. It's on paper somewhere, unfortunately I don't know where and I'd have to redo the math at this point. But if you're interested, let me know. It's not too difficult to measure the orientation of the baseline between the two using Google Earth though ..)
On Dec 26, 2007, at 11:08 PM, Chiu-Teng Tsai wrote:
Dear all,
I am Chiu-Teng Tsai (BM6ERA) from Taiwan. Now we are building a mobile ground station. One of our problem is how to calibrate the azimuth angle. Use compass only, or any better solution? Thanks for your help!
Best regards,
Chiu-Teng Tsai
Crumley: "How can we expect people to buy things if some Person is giving them away? Now please go and get him out of here." Nobby: "Arrest the Hogfather, style of thing?" Crumley: "Yes!" Nobby: "On Hogswatchnight?" Crumley: "Yes!" Nobby: "In your shop?" Crumley: "Yes!" Nobby: "In front of all those kiddies?" Crumley: "Y-- You think that will look bad?"
(: HAPPY HOGSWATCH :)
At 04:11 PM 12/28/2007, Bruce Bostwick wrote:
Not meaning to trash compasses, just have had some less than satisfying experiences using them to align antennas on satellites due to the number of sources of measurement errors that have to be accounted for. I've used some very good compasses (my favorites are the ones from Morin that allow sighting across the compass to get a magnetic bearing of a landmark on the horizon :) but getting accurate true north out of even a good magnetic compass is a lot of work ..
Well, I rely on magnetic compasses not to get lost, and use maps that are most often aligned to grid North. I have managed accuracy far better than that to aim most antennas (maybe a high gain 10 GHz dish might have issues, but anything else I could get it near enough). Mind you, there were a LOT of other good suggestions here as well.
Like any tool, it comes down to practice in using it. Avoiding magnetic interference to compasses is akin to avoiding QRM when trying to work weak signals. :)
73 de VK3JED http://vkradio.com
I'm new to satellite stuff, I haven't heard a satellite yet, but I feel my moment is coming. I live in San Francisco, on top of a hill in the middle of a swirling vortex of RFI.
For the time being I'm sticking an Arrow II out the window. I get this reasonably strong CW signal at 436.804 MHz. It's annoying and right on top of a common downlink frequency.
So, to make a long story short, the source of the signal was me. I bring the antenna inside and start poking around and it's coming from a Linksys WAP55AG 802.11 (A+G) access point. Evidently, it's doing a little 70cm work as well:
http://www.mock.com/test/spacetrack/wap55ag-rfi.png
One down, hopefully I can hear something 2k miles away rather than 2-meters away.
jeff AD6EO
Instatrack will give you the azmuth and elevation of the Sun vs time. Use GPS for time and You now have an accurate calibration.
Art, KC6UQH ----- Original Message ----- From: "Jeff Mock" [email protected] To: [email protected] Sent: Thursday, December 27, 2007 5:15 PM Subject: [amsat-bb] Re: How to calibrate the azimuth angle?
Well, now that everyone has trashed compasses. Here's the compass that I really really like:
Click on "precision instruments", it's the Suunto Tandem. It's a compass and clinometer in a nice machined aluminum package. It has optical sites for both instruments that really improves accuracy (if you ask me). It's really well made and it's from Finland... If nothing else, you can walk around measuring the height of trees.
jeff
Bruce Bostwick wrote:
A compass won't give you accurate azimuth unless you know for sure that you're not near any large masses of metal, and even then, you will need to know your local magnetic deviation. I tried to use a compass to align a satellite dish once, and it put me so far off on the azimuth I never did find the satellite that way, even taking magnetic deviation into account. You might have better luck where you are, but it's a lot of work to do it that way even if it does work.
A much easier solution is to look at your location in Google Earth and find the orientation of a nearby road, and use that as your azimuth reference. That automatically gets you azimuth relative to true north, which makes the job considerably simpler. If you don't have nearby roads that are straight enough to be useful, find a distant visible landmark (like a radio tower) and determine what its azimuth is from your location, then use it as a reference point and find your desired azimuth from there. (A long time ago, I worked out a formula for determining the bearing to a distant landmark using only the latitude and longitude of it and the observing location. It's on paper somewhere, unfortunately I don't know where and I'd have to redo the math at this point. But if you're interested, let me know. It's not too difficult to measure the orientation of the baseline between the two using Google Earth though ..)
On Dec 26, 2007, at 11:08 PM, Chiu-Teng Tsai wrote:
Dear all,
I am Chiu-Teng Tsai (BM6ERA) from Taiwan. Now we are building a mobile ground station. One of our problem is how to calibrate the azimuth angle. Use compass only, or any better solution? Thanks for your help!
Best regards,
Chiu-Teng Tsai
"On this one we'd like to think of ourselves collectively as 'da men', sir." -- Toby Ziegler
Sent via [email protected]. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
Sent via [email protected]. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
Instatrack will give you the azmuth and elevation of the Sun vs time. Use GPS for time and You now have an accurate calibration.
Yes, indeed, Art, I use InstantTrack all the time, just for that, but assume that people would not buy it just for that. Wish the tracking part was compatible with XP, but everything else works on XP....I use the sun to set AZ/EL on my dish at 2.4 gigs, and it couldn't be simpler...
I use Sat PC32 to control my rotors, and freq...wish he had the sun, moon on it also....
Stop in some day if you are in this direction...
73, Dave, WB6LLO [email protected]
Disagree: I learn....
Pulling for P3E...
----- Original Message ----- From: "Chiu-Teng Tsai" [email protected] To: [email protected] Sent: Thursday, December 27, 2007 6:08 AM Subject: [amsat-bb] How to calibrate the azimuth angle?
Dear all,
I am Chiu-Teng Tsai (BM6ERA) from Taiwan. Now we are building a mobile
ground station. One of our problem is how to calibrate the azimuth angle. Use compass only, or any better solution? Thanks for your help!
Best regards,
Chiu-Teng Tsai
Hi Chiu, BM6ERA
My reference source to calibrate the azimuth angle is the Sun at the equinox. I am fortunate enough because my horizon is free over the sea and I know exactly the point near the island of Ischia in wich the sun set belove the horizon during the spring equinox on march 21 and the autumnal equinox on september 23
http://it.wikipedia.org/wiki/Equinozio
This reference point over the sea when the sun set during the equinox is my geographical West or AZ=270 degrees
For several reason this point it is not accurate enought for precise astronomical observation but it is accurate enought to calibrate my AZ=270° if the beamwidth of my antenna at - 3 dB points is in the order of 34 degrees like for my 13 dBdC 2M-22C for 2 meters or 25 degrees like for my 15.2 dBdC 435-40CX for 70 cm.
By the way the above metod is not to be used for my 1.2 meters disc at 2400 MHz or any larger disc or yagi array for EME
In the case of 1.2 meter disc the gain is 27 dBi at 2400 MHz and the beamwidth at - 3dB points is only 7 degrees but more important the feed rarely is perfectly centered in the focal point so that the pencil of the antenna can be affected by an unwanted "squint" angle.
If I point a disc on the sun and I look at the shadow of the feed in the center of the disc probably the pattern of the antenna is not perfectly oriented towards the sun because of the "squint" affecting the feed.
For the above reason when the gain and directivity of the antenna are very large I use InstantTrack to know with sufficient accuracy the Az and El at the time of measuring the maximum level of sun-noise at the output of my receiver and so now I can accurately calibrate my AZ and EL readout accordingly.
Best 73" de
i8CVS Domenico
participants (18)
-
Alan -
Auke de Jong, VE6PWN -
Bruce Bostwick -
Chiu-Teng Tsai -
Dave Guimont -
Franklin Antonio -
Gabriel - EA6VQ -
George Henry -
i8cvs -
Jeff Mock -
Jim Sanford -
Joe -
John Franke -
kc6uqh -
Luc Leblanc -
Michael R. Owen -
Ollie Eisman -
Tony Langdon