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tilting a yagi?

S

spitzer

Member
May 11, 2011
3
0
11
Hello,
I have been considering a beam antenna to improve my chances to get into Europe. I would invest in a Yagi and a modest tower if I thought it would do me any good.
reason: I have some hills in that direction (about 1/2 to 1 km from QTH, elevation estimated at 13 to 15 degrees). My question to those who have experience with Yagis is: Would tilting it up slightly eliminate some of the refraction/reflection I would encounter hitting those hills straight on - or wouldn't it make any difference? If the tilt was a reasonable idea, would the height of the tower then really be terribly important? ( I was thinking 40 to 50 feet or so).
Appreciate any input!
 
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You will see the greatest benefit from slightly tilting the beam to your visual horizon. For someone on flat ground, that is a slight downward tilt.
 
aiming a yagi over an obstruction

C2 said:
You will see the greatest benefit from slightly tilting the beam to your visual horizon. For someone on flat ground, that is a slight downward tilt.
Click to expand...

But that, C2, would point it right into these hills, wouldn't it?
 
Just put the antenna up as high as you can in the horizontally polorized orientation and don't be concerned with "tilt". It won't make any difference at frequencies under 30 Mhz.

If I were you I'd also post this question on eHam. I'm sure the antenna experts will give you the detailed version of "just put it up as high as possible" and start making contacts. The hill will have less effect on your signal than the height of the antenna above ground.
 
C2 said:
You will see the greatest benefit from slightly tilting the beam to your visual horizon. For someone on flat ground, that is a slight downward tilt.
Click to expand...

I don't buy it. If anything, you'd lose gain from the elements being misaligned I think.
 
359 said:
... you'd lose gain from the elements being misaligned I think.
Click to expand...

the "re-enforcing" beam width (capture area) is MUCH wider than the "mis-alignment".


i do know of a cb'er that tilts a verticle gp about 30 degrees, he claims it works "better" :pop::pop:
 
spitzer said:
But that, C2, would point it right into these hills, wouldn't it?
Click to expand...

You were suggesting pointing it upward. You might find that pointing it up helps, you might also find that pointing it down helps. The variables are far too complex and it would depend on the exact circumstances at that particular time.

In general, your signal goes up anyway and changing the vertical orientation of your boom is going to have unpredicable results. The best thing to do is try different things.

Yeah, pointing a vertical towards your contact helps because the signal shoots off the end like boolets from a gun...well, who knows exactly how it would affect the radiation pattern?

Do we have any modelers?
 
Here are some links for reading, both have great info.

tilting an yagi for HF does squat for the signal as all HF signal reflect off the ground.

Dipole Antenna Radiation Patterns by WB4YJT

notice the low angle of radiation is at 1/2 wl above ground.

the higher the antenna is installed the more lobes shooting off into higher angles of radiation, But the secondary lobe is at an even lower angle of radiation thus producing better DX potential.

Next link is for height vs distance

http://www.arrl.org/files/file/antplnr.pdf

the last paragraph in this paper sums it all up.

you will find a chart in this link to show how high to install your yagi compared to what your target area of the world is.

Depends where you are wanting to work into

Fig 6 will show you the graph for 10 meters, it applies to 11 meters also as well as 12 as they are pretty close in freq.

shooting DX is not a coin toss. If you have a good gain yagi installed at the right height for your target area it works great.

I run normally 100 watts, on 20 meters and up, never need an amplifier, and bust pileups, the antennas are at the right height for EU, into Ja land I use the vertical as it is 20 feet higher than the yagis, some times I can not even hear the Asian stations on the yagi but I can work them on the vertical, difference of 20 feet in height.

the received signal arrives at a low angle of radiation and the antenna also has to be at the proper height to receive the signal.

There are some exceptions, the N4GG array is a wire antenna, phased verticals that work killer on low angle DX, easy to build and need not install at height. google is your friend here.

Good luck on getting into EU and hope the info helps on your install.
 
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If there was in fact any difference at all (doubtful) , tilting a yagi up or down would equate to slewing it in the azimuth an equal amount. The beamwidth of the average HF yagi is too wide for any advantage of beam tilt unless you want it to look like a hurricane hit it. Take off angle is more a function of height above ground than it is of beam tilt on HF. Commercial FM stations use a phasing technique to effect beam tilt and even then it is only a few degrees.
 
tilting up a yagi

Thank you all who responded,
esp. Wavrider for th excellent links with the primer
on propagation patterns!
Things are a bit complicated.
It is tough to invest thousands (10?) of dollars for a tower if the outcome
is less than certain.
The N4GG array looks better by the day!
 
You are welcome on the info and the links.

Now maybe take a look at verticals, A good vertical installed at height gives good low angle of radiation and is light weight, does not need a rotor.

I put an imax 2000 at 70 feet, have worked into EU, S. America and the Pacific when the band opens.

I prefer the yagi for the rejection as the bands do get crowded but the vertical does work.
 

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