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Author Topic: Inverted V yagi aiming up into the sky  (Read 350 times)

Offline OgreVorbis

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Inverted V yagi aiming up into the sky
« on: July 19, 2019, 0147 UTC »
So I'm curious why I have not seen this type of antenna before. Basically what it would be is 3 or more inverted Vs stacked on top of each other along the length of the mast. I've seen something somewhat similar with inverted Vs, but not aiming upwards. With HF, we want the signal in the ionosphere, so why not aim it up? Why do hams always aim their yagis horizontally?

And when I say aiming up, I want to be clear. I do know that hams mount horizontally and vertically which is not what I'm talking about. I mean the yagi is pointing up into the sky. I figure with a dipole, the radiation angle wouldn't be right, but with an inverted V I think it would. Plus, it is much easier to install.
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Online Brian

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Re: Inverted V yagi aiming up into the sky
« Reply #1 on: July 19, 2019, 1744 UTC »
Aiming up will give very short distance reception.
Also, think of the height of mast you would need for a properly spaced Yagi pointing upwards.  It would be impractical for me to do it anyways.

As an aside, I had to collect a relative from an airport a few years ago. We decided to do a bit of sightseeing on the way home and came across a strange antenna setup several miles from the airport. One seemed to be a "T" antenna mounted between utility poles and another was a yagi or log perodic pointing straight up towards the sky. I think I should have pics of them somewhere here on a hard drive. Finding them is another thing though.........

Nice thunder storm kicking off here now.
« Last Edit: July 19, 2019, 1802 UTC by Brian »

Offline Josh

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Re: Inverted V yagi aiming up into the sky
« Reply #2 on: July 19, 2019, 1806 UTC »
If the array is tuned to 12mHz or lower, it'll be a fantastic nvis antenna when luf/muf are in that range of freqs. In this mode, the rf goes straight up, hits the ionospheric layer, is reradiated by the ionosphere and sent more or less straight back down, with a radius of several hundred miles being typical. There will be no skip zone inside this radius, outside the radius the signal may go unheard. These effects are why military units often employ nvis; no skip zone plus difficulty in direction finding on a signal that comes from straight up.

Otherwise you have a neat array to listen to the galaxy on hf when muf is lower than the tuned freq, as the ionosphere is passive to signals higher than muf. You can hear Jupiter on 21mHz, for example.
https://vimeo.com/173638603
« Last Edit: July 19, 2019, 1808 UTC by Josh »
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Offline OgreVorbis

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Re: Inverted V yagi aiming up into the sky
« Reply #3 on: July 20, 2019, 0510 UTC »
I was thinking maybe this would be more useful on medium wave.
The optimal height above ground for a dipole is 0.6 wave, but 1/4 wave comes in pretty close.
AM broadcasting has always been hard because of the height required and the high ground losses in my area.
If I made such a yagi or log periodic on MW band, do you think it would be more effective at getting the energy into the ionosphere than just having it at the correct height?

I mean, with a standard dipole isn't a lot of energy just being absorbed into the ground?
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Offline Josh

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Re: Inverted V yagi aiming up into the sky
« Reply #4 on: July 20, 2019, 1905 UTC »
Ever notice how no ambc station uses a horizontal antenna?

This is due most ambc stas are focused on the local market, and the local market is listening during the daytime for the most part. Since the target audience listens during the day, the sun is out, and that creates a huge problem for ambc signals. The sun energises the D layer in the idunnosphere, and the D layer eats ambc sigs like no other.

So the way around that is to use vertical polarisation as that polarity is devoured least by the D layer.

That being said, at night when the D layer dissipates and the F layers merge into one super F layer and the ambc dx is rolling, once a sig hits the F layer the originating polarisation goes out the window and can be anything, even rotating.

So the question is, do you want to rx local daytime sigs or nighttime?

If local daytime sigs, a vertical will be your best bet, if dx is desired, pretty much anything should work.

And yes, as you questioned, low dipoles are worm heaters, you have to be up about a halfwave to really reduce the ground losses, but higher would be better. Simply getting the feedpoint of a inverted v up above 1/4w helps, as the feedpoint is where current is max and that is where the radiation is most intense. The ends, the high voltage do not touch points, can be low to the ground, just don't touch em.
« Last Edit: July 20, 2019, 1910 UTC by Josh »
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Offline skeezix

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Re: Inverted V yagi aiming up into the sky
« Reply #5 on: July 20, 2019, 1959 UTC »
As an aside, I had to collect a relative from an airport a few years ago. We decided to do a bit of sightseeing on the way home and came across a strange antenna setup several miles from the airport. One seemed to be a "T" antenna mounted between utility poles and another was a yagi or log perodic pointing straight up towards the sky. I think I should have pics of them somewhere here on a hard drive. Finding them is another thing though.........

What you described sounds like an NDB (the T antenna between two utility poles) and a marker beacon for the second one. They're co-located so I'm guessing that's the probably the final approach fix for one of the runways at that airport.

This is one version of a marker beacon transmitter antenna:
https://i1.wp.com/s0.geograph.org.uk/photos/74/66/746699_4531334a.jpg


Which airport was it near?


Minneapolis, MN

Online Brian

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Re: Inverted V yagi aiming up into the sky
« Reply #6 on: July 24, 2019, 2109 UTC »
As an aside, I had to collect a relative from an airport a few years ago. We decided to do a bit of sightseeing on the way home and came across a strange antenna setup several miles from the airport. One seemed to be a "T" antenna mounted between utility poles and another was a yagi or log perodic pointing straight up towards the sky. I think I should have pics of them somewhere here on a hard drive. Finding them is another thing though.........

What you described sounds like an NDB (the T antenna between two utility poles) and a marker beacon for the second one. They're co-located so I'm guessing that's the probably the final approach fix for one of the runways at that airport.

This is one version of a marker beacon transmitter antenna:
https://i1.wp.com/s0.geograph.org.uk/photos/74/66/746699_4531334a.jpg


Which airport was it near?

Knock International Airport in the west of Ireland.

Searched my HDs but can't locate the pics, nor the location on Google Earth.

Offline Boriken

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Re: Inverted V yagi aiming up into the sky
« Reply #7 on: July 25, 2019, 0039 UTC »
Might be this one?

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