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Old 03-13-2012, 01:02 AM
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BTW, since when did 11m=33'?


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Old 03-13-2012, 01:18 AM
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A Imax 2000 or any 5/8 wave antenna one wave length above the ground yields the avails the lowest angle of radiation to the horizon.
It also optimizes DX:




Antennas Elevation Angle in Degrees

Vertical
1/4 wavelength long 28 (15 - 40)
3/8 wavelength long 23 (12 - 35)
1/2 wavelength long 18 (09 - 25)
5/8 wavelength long 12 (07 - 18)

Hortizontal Dipole
1/8 wavelength long above ground 90 (55 for lower 3db point)
1/4 wavelength long above ground 60 (38 - 82)
1/2 wavelength long above ground 30 (18 - 40)
3/4 wavelength long above ground 21 (14 - 28)
One wavelength long above ground 17 (09 - 19)

Hortizontal Yagi
1/4 wavelength long above ground 43 (32 - 54)
1/2 wavelength long above ground 30 (18 - 38)
3/4 wavelength long above ground 21 (13 - 28)
One wavelength long above ground 17 (09 - 18)

From:
Antenna height vs skip angles
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Old 03-13-2012, 01:25 AM
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Quote:
Originally Posted by Robb View Post
A Imax 2000 or any 5/8 wave antenna one wave length above the ground yields the avails the lowest angle of radiation to the horizon.
I agree that raising an antenna will lower the radio angle, but nothing special happens at 36'.




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Old 03-13-2012, 01:47 AM
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Quote:
Originally Posted by 359 View Post
I agree that raising an antenna will lower the radio angle, but nothing special happens at 36'.




Damn, I wish I could understand this graph. It looks like some one transmitting at the North Pole and the signal is being sent east against it's will.

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Old 03-13-2012, 04:46 AM
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That formula is close enough for 'LOS' propagation. The thing to remember is that HF, the 11 meter band, is not 'LOS' to start with. The 'radio horizon' isn't the limit for HF.
How much improvement will be seen by raising/doubling the height of an antenna? If you can ever quantify that for any particular band you could make a fortune. Unfortunately, there's no way to predict that sort of improvement, how much it'd be, just way too many other things affect reception than just antenna height. I think you would be safe in thinking that it would be a noticeable difference. After that, your guess is as good as anyone else's.
I agree about the 'wave length' theory, don't put much faith in it. If done correctly, an antenna will work okay mounted at ground level. The higher you can go with it (done correctly) the better that "okay" becomes.
Do it, then you can tell us how much it improved things!
- 'Doc

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Old 03-13-2012, 10:58 AM
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Quote:
Originally Posted by W5LZ View Post
That formula is close enough for 'LOS' propagation. The thing to remember is that HF, the 11 meter band, is not 'LOS' to start with. The 'radio horizon' isn't the limit for HF...
agreed,............. I have a 6 meter quad on a hazer, and often there is a marked difference when I run it up or down on the electric winch.

but, thats 6 meters, one of these days I'm gonna put an HF antenna on the hazer and play with it<>

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Old 03-13-2012, 12:57 PM
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The DX advantage is optimal when the antenna is brought to one wavelength. However, you get what you pay for in this regard. It has other consequences, as Captain Kilowatt pointed out:

Quote:
Having the lowest take-off angle is great when wanting to work halfway around the world; or close to it. But there are times when having a really low angle is not desired. Such as when the band is open to an area only a few states away. That is when having a higher take-off angle is better. A higher take off angle actually lays down a stronger signal into the closer target area than a low angle.
Sooo - DX 'tuning' depends on what freq is used, type of antenna and its take-off angle, and how high you put it up.
Food for thought.
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Last edited by Robb; 03-13-2012 at 01:25 PM.

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Old 03-13-2012, 01:31 PM
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