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{
    "url": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/VRCDTCJEKHGBWOMWXT3T3JC6LTLJOPJ7/?format=api",
    "mailinglist": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/?format=api",
    "message_id": "[email protected]",
    "message_id_hash": "VRCDTCJEKHGBWOMWXT3T3JC6LTLJOPJ7",
    "thread": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/thread/VRAZHFDIIVIFCNUWFWMWTVNCYB2X73VE/?format=api",
    "sender": {
        "address": "antonio (a) qualcomm.com",
        "mailman_id": null,
        "emails": null
    },
    "sender_name": "Franklin Antonio",
    "subject": "[amsat-bb] Re: How to calibrate the azimuth angle?",
    "date": "2007-12-27T20:29:26Z",
    "parent": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/VRAZHFDIIVIFCNUWFWMWTVNCYB2X73VE/?format=api",
    "children": [
        "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/Q7MG5UWKINLAK5TSI5N66SPOOZLXUEAQ/?format=api"
    ],
    "votes": {
        "likes": 0,
        "dislikes": 0,
        "status": "neutral"
    },
    "content": "At 09:08 PM 12/26/2007, Chiu-Teng Tsai wrote:\n>    I am Chiu-Teng Tsai (BM6ERA) from Taiwan. Now we are building a \n> mobile ground station. One of our problem is how to calibrate the \n> azimuth angle. Use compass only, or any better solution? Thanks for your help!\n\nI agree with the comments of others re two methods that work \nwell:  The stick in the ground, and tracking the sun.\n\nCompasses are very difficult to use to get an accurate \ndirection.  First there's the issue of magnetic declination or \nmagnetic variation, caused by the fact that the magnetic north pole \nis not at the north pole.  You look up a number on a map or \nsomething, but most people frankly can't remember whether you're \nsupposed to add the number or subtract it.  This is a mess.  But \nthat's not all.  Local iron (nearby cars, pipes in your house, or \neven the mast of your antennas can affect the reading more than you \nmight imagine.  (This is called magnetic deviation.)  Sure, mariners \nhave been using compasses for a zillion years, but they've studied \nvariation and deviation, and calibrated their compasses for the \nmagnetic effects on their boats, and have done it routinely over many \nyears to keep themselves reminded of the details.  The weekend \nantenna putter-upper has not.  (With the advent of GPS etc, fewer and \nfewer mariners every day know how to use a compass.)  Compasses on \nboats are nailed down, so that it is possible to calibrate out the \neffects of other (also nailed down) metal.  When you're walking \naround with a compass, you don't have this luxury.  I once tried to \nuse a compass on an outing to figure out where to point an antenna, \nand as I walked around I kept getting different readings.  Finally I \nrealized that if I was anywhere near my car, the compass pointed \ntoward my car.  With a handheld compass you just have to stay far \naway from cars, houses, antenna masts, etc.  You can't hold it in \nyour left hand as you hang on the side of the steel tower tightening \nthe rotor bolts, and expect success.  With enough care, a compass can \nwork, but getting an accurate reading is more difficult than most \npeople presume.\n\nI say just say no to compasses.  Use the stick in the ground or \ntracking software that can point your antenna at the sun.\n\nI suggest you start with the stick.  That will give you enough info \nto assemble the system, tighten down the bolts, etc.\n\nPointing the antenna at the sun is the best final check, because it \ndouble checks so many pieces of your system.  If you put the stick in \nthe ground, that may make you know which way is North, but it doesn't \nmean you tightened down the screws with the mast in the right \nposition, or calibrated the rotor control software right, or have the \nright timezone in your computer, etc.\n\nWith a Yagi antenna, because it is long and skinny, its shadow is a \nreally accurate indication.\n\n",
    "attachments": []
}