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AZ / EL Alignment Questions...

Discussion in 'Satellite and Space Communications' started by N8NMG, Oct 15, 2021.

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  1. N8NMG

    N8NMG Premium Subscriber QRZ Page

    Hello all,
    1st I am a mostly total nOOb on HamSats. I did read a bunch of articles from AMSAT about LEO Sats, Oscars, etc. So I decided to score an Elk antenna and do SO-50. That went okay! Then I decided to do a full blown AZ /EL setup.

    One day at a "trunk fest" I scored a pair of cross polarized beam antennas for HamSats. One is 2m the other is 70cm and the price tag was perfect for both. Photo is on my page at https://www.qrz.com/db/n8nmg

    Slowly I acquired all the bits and pieces... ICOM IC-970A, Track Box, AZ/EL rotors, mast, boom, cables, and poof after many hours I have a working AZ / EL setup. It tracks, and doppler shifts as expected. However I am having some strange results with my alignment. I found out my compass is a great paperweight, and that's about it. I know how to do Land Navigation quite well after several years in the service, and this compass will indeed get you lost or worse. Name brand compass is on order, compass like paperweight destined for the dumpster.

    So my AZ / EL alignment questions...
    1. Polar Alignment - anyone have success with nailing both Azimuth and Elevation alignment with the North Star? If so how did you do it? I was thinking of using a rifle scope and zip ties / duct tape / bubble gum... something.
    2. Azimuth alignment - anyone have success nailing true north with a lensatic / magnetic compass? If so what was your technique?
    3. Elevation alignment - anyone have success nailing horizontal zero degrees / vertical 90 degrees? How? Bubble levels?
    4. Solar / Lunar alignment - ever try it? Did it work?
    5. What about EME? Any special alignment tips / tricks / hints?
    Any tips, tricks, hints, magic spells, voodoo, or scholarly articles will be greatly appreciated.
    Thanks!
    73 es gud dx de N8NMG
     
  2. K7WDO

    K7WDO Ham Member QRZ Page

    Here's a few fun ones for checking aim:

    For elevation, just use a compact level. Set the rotor to 90 degrees, slap the level on the antenna's boom, and see if it's square. Do the same at zero elevation. You can also be fancy and use an inclinometer held up against the antenna boom to check elevation if you want to check more than just 0 or 90 degrees.

    If your antennas are center mounted, you can set the rotor at 90 degrees (straight up), loosen the antenna bracket and let gravity pull the back of the antenna straight down. Just tighten things back up and you should be reasonably straight if you need to do something quick and dirty.

    If you want to check azimuth, TV stations work great as a reference point. You can find online tools (tvfool.com, rabbitears.info, etc.) that will give you the headings (both true and magnetic north) to the stations. 2m is below channel 7 (VHF high) and 70cm is just below channel 14 (UHF). Just plug your antenna into a TV that can show signal strength (usually under signal diagnostics in the menus) and tweak up the aim based on the signal. From there, check to see how close your aim is on the rotor to what the website says the heading should be. If your antennas are lined up properly, the headings should be a fairly close match.

    Satellite tracking software gives the azimuth aim based on true north (0 degrees is the north pole) while a compass aims at magnetic north so that can sometimes get a little confusing if you're doing the initial aim with a compass. Nearby metal objects (rotors, tower, etc.) can also interfere with a compass taking a magnetic reading and end up pointing you in the wrong direction so it doesn't hurt to check your compass heading a few steps away from the antennas.

    Antennas have a pattern to them (beamwidth) where they can still pick up the signal even if you're not 100% dead on. Generally, the bigger the antennas is and higher the higher the gain, the more narrow the beam is:
    M2 2MCP8 - 9.2 dB - 60 degrees
    M2 2MCP14 - 12.3 dB - 52 degrees
    M2 2MCP22 - 14.4 dB - 38 degrees
    So if you're working with a high gain antenna (or a really high frequency - GHz range), accurate aim is important, but at lower frequencies where your antenna has a wider beam, you have a lot more wiggle room. So if you're working with smaller antennas at 2m/70cm, being off by a degree or two is not going to kill your reception. (Comes in handy if you're asleep at the rotor controls during a pass)

    Hope this helps and have fun with the new antenna setup.
     
    N8NMG and KS1G like this.
  3. KS1G

    KS1G Ham Member QRZ Page

    Night time - aim antennas at Polaris. Daytime - find an app that gives the current sun azimuth and elevation. fine-tune for minimal shadow (don't sight down antenna boom at sun!). Or same using app that gives az/el for Moon (won't burn out eyeballs when you forget not to look directly at sun :cool:). If you live where the difference between magnetic and true North is small, use a compass and level and don't worry about it too much unless your antennas have like 10 deg or less beamwidth. Computer control apps like SatPC32 have ability to trim/fine tune the azimuth and elevation so you don't have to keep pulling out the wrench set.

    EME - A local ham was running EME with low-elevation ground gain with a single 9 element horiz polarization yagi and about 150-300W (I forget) with the outboard amp in a weather-resistant box at the antenna. He had a pretty quiet location, good shot at moonrise and moonset, and could make QSOs with the largest stations (they're doing most of the work). He later upgraded to a pair of either 9 element or slightly larger antennas to work more stations. YMMV. I have too many obstructions and local RFI to make EME feasible at my QTH, or I'd see what if I could decode anything with my 2MCP14 (7 el x 2 circ polarized).
     
    N8NMG likes this.
  4. KD9VV

    KD9VV Ham Member QRZ Page

    "Polar Alignment - anyone have success with nailing both Azimuth and Elevation alignment with the North Star? If so how did you do it?"

    "Polar Alignment" isn't quite the right words when finding N-S-E-W.
    Polar alignment is more for us amateur astronomers who need our telescopes
    to follow celestial motions.

    All depends how accurate you want to be.
    As already mentioned, antennas have a beam width, almost always enough to acquire the SAT within several degrees H plane and E plane.

    I once for fun as a amateur astronomer mounted my 2M 432Mhz antennas on my EQ6R telescope mount. LINK
    Talk about accuracy! There is not a az/alt rotor program that can rival this accuracy.
    Again, you don't need this sort of accuracy.

    Also, on or about Sept 21 we have the autumnal equinox; it is the only time the sun rises 090 degrees and sets 270 degrees.

    There are many programs (free) that will give you positional data on the sun, moon, stars etc...
     
    N8NMG likes this.
  5. N4UFO

    N4UFO Ham Member QRZ Page

    What I did to align my AZ-EL antennas was look at a satellite view of my home on google maps. I pinpointed the antennas location and found a distant object (tree) a couple houses up the street that was due north. Then went out and stood on a ladder and aligned the boom of the antennas with the distant object by sight.

    Yep, I'm different. :)
     
    VE3CGA, N8NMG, KB1PVH and 1 other person like this.
  6. VE3CGA

    VE3CGA XML Subscriber QRZ Page

    for EL, its checked with a level at 90 and 0
    for AZ, luckily I can see polaris and can aim the antennas toward that. That would be my 0 deg and 360 deg point

    One thing comes to mind, check to see if the yagis are parallel and not toeing out or in. I imagine a couple degrees at ground level could be quite an error out in orbit. I guess antenna beamwidth would minimize that error
     
    N8NMG likes this.
  7. N8NMG

    N8NMG Premium Subscriber QRZ Page

    R R R VE3CGA
    Thanks for the tip on "toe in" on my beams. I read your post and looked. DANG! Toe in. Time for more adjustments.
    73 es gud dx de N8NMG
     
    VE3CGA likes this.

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