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Author Topic: Antenna Direction  (Read 492 times)
N0DSN
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Posts: 13




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« on: March 25, 2010, 04:09:40 PM »

I am getting ready to install my first rotor (Ham IV). My question is what is the best way to get the antenna's to face the same direction as the control box. I would like to use the bearing distance on my logging software and get the antennas as close as I can to this. Thank You for any help.
73
KD0BFP
Dustin
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WT0A
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Posts: 922




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« Reply #1 on: March 25, 2010, 04:15:16 PM »

set your rotator to whatever then when you clamp the mast in the rotor make sure ant is pointed that way.
Glen
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N0DSN
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Posts: 13




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« Reply #2 on: March 25, 2010, 04:16:19 PM »

I should have mentioned this. I did see some suggestions on one previous post but can't seem to find that same post again by doing a search.
Thanks
KD0BFP
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WB2WIK
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Posts: 20545




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« Reply #3 on: March 25, 2010, 06:28:33 PM »

The way everybody aligns rotators and antennas is by using a compass and then adding or subtracting the magnetic declination for your location.

I know where true north is from here, so I always set my rotator control boxes at "north," and then clamp down the mast when the antennas are aimed north.  Pretty simple.

Great circle bearings and such have absolutely nothing to do with this.
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WA3SKN
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Posts: 5437




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« Reply #4 on: March 26, 2010, 04:55:20 AM »

You need to know where true North or South is.
Many use the Pole Star in the northern hemisphere, and from your call I will assume this will apply to you.  Remember there is a difference between magnetic and true north, so if using a compass include a "correction".
Set control box to "north".  Mount antenna pointing north.
73s.

-Mike.
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AA4PB
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Posts: 12685




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« Reply #5 on: March 26, 2010, 05:16:46 AM »

I always set the rotor to center scale (either N or S, depending on how you have it set). Then mount the antenna pointing that direction. The benefit of using center scale is that you can dress the coax so that only needs to wrap 180 deg in either direction.
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K7UA
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Posts: 37




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« Reply #6 on: March 26, 2010, 10:33:03 AM »

Good advice here.  Just in case you don't have a good compass, you can always use the north star as a reference.  It is not hard to find.  Also, HF beams do not have pin point beam widths.  Getting it pretty close will suffice.
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WB6BYU
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Posts: 13028




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« Reply #7 on: March 26, 2010, 01:02:48 PM »

And if you don't have a compass and don't want to climb the tower at night to line
it up with Polaris, there are a couple other options.

What direction do the nearest roads run?  Often they they are North/South or
East/West.  The one by my house runs North/South as close as the surveyor
could make it.  If my tower is 150' off the road, I can look at the farm a half
mile up the road and guess where 150' from the road would be.  That's probably
closer than I'll get with a compass.

Or find when local noon is at your location (it is a function of your longitude
relative to the center of your timezone.)  At that point the sun is due south,
so you can line up your antenna so the  boom makes the narrowest shadow.

If there is a local landmark (hill, building, etc.) that you can see from your
tower and also locate on a map, measure the bearing on the map with a
protractor, set the rotator to indicate the expected bearing, and clamp down
the boom so it points to the object.
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AA4HA
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Posts: 1378




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« Reply #8 on: March 26, 2010, 01:40:38 PM »

A good ham can make a compass with a hank of reindeer hide and broken PL-259 connector.
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Ms. Tisha Hayes, AA4HA
Lookout Mountain, Alabama
N0DSN
Member

Posts: 13




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« Reply #9 on: March 26, 2010, 06:32:13 PM »

Thanks for all the replies and useful information. I do have a road that runs north/south and one also east/west. Again I thank all of you for the info.
Hope to get up beginning of the next week.
Thanks 73
KD0BFP
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W8ATA
Member

Posts: 320




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« Reply #10 on: March 27, 2010, 07:25:28 PM »

You got lots of good advice on setting direction. One other thing you may want to consider during your set up is whether you want your system, rotator and beam, south or north centered. I think Ham IV's produced in the past several years come with a reversible meter face. Where I live at about 40 north I have my system south centered. Just something for you to think about.

Good job on you license level in a short time. Best to you.

73,
Russ
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W5RB
Member

Posts: 565




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« Reply #11 on: March 27, 2010, 08:05:44 PM »

Magnetic declination for your licensed location is 59 minutes ( a hair less than 1 degree ) East . Hardly worth trying to correct for that . If you can see identifiable commercial towers from your locale , very precise info on their location is available on the FCC website , and you can visually check your bearing against them .

http://www.magnetic-declination.com/
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K6AER
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Posts: 3483




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« Reply #12 on: March 27, 2010, 09:39:28 PM »

This is not rocket science. Walk to the base of the tower. Press here on your GPS. Walk north about 100 feet until the readout is 180 degrees to the set point. Put a stake in the ground and you are true north of the tower.

Now for the hard part.....Set the rotor to north and climb the tower and point the antenna at the stake. Fasten the clamp bolt down and enjoy.
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VK1OD
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Posts: 1697




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« Reply #13 on: March 27, 2010, 09:51:46 PM »

This is not rocket science...

When you think you have it right, point the antenna so you can look down the boom from a street location a couple of hundred metres (or yards) away, then go take a compass shot back along the boom. Try it from a few locations where you should get good compass readings. After adjusting out magnetic declination, what is the mean error wrt expected beam width?

Owen
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