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what is this antenna for?
- Thread starter LarryLock
- Start date
I think you truncated the URL. You probably meant
- Thread starter
- #3
Yes, thank-you geekee. Does anyone know what this is for???
MikeHalloran
Mechanical
Looks like a helicopter trap to me.
;-)
Mike Halloran
Pembroke Pines, FL, USA
;-)
Mike Halloran
Pembroke Pines, FL, USA
Hi,
I estimate length = 100m. It is a lambda/4 monopole (two together). So wavelength is about 750KHz.
They are separated by about 5 metres. The near field of one monopole is 2D^2/lambda = 50 metres. -So, they are both in each others' near fields. Therefore, the antenna pattern will be optimised to receive/transmit from/to a particular direction.
-A good idea!........How else could you get good optimised directional properties from an antenna of such low frequency?....you certainly couldnt have a dish for that wavelength. And having two antennas the same means manufacturing is more straight forward.....not only that, but two together joined at top and bottom is less likely to blow over in the wind.
A yagi would be another idea.....but can you imagine suspending the parasitic elements up there in the sky?.....better just make two the same and shove them together.
I estimate length = 100m. It is a lambda/4 monopole (two together). So wavelength is about 750KHz.
They are separated by about 5 metres. The near field of one monopole is 2D^2/lambda = 50 metres. -So, they are both in each others' near fields. Therefore, the antenna pattern will be optimised to receive/transmit from/to a particular direction.
-A good idea!........How else could you get good optimised directional properties from an antenna of such low frequency?....you certainly couldnt have a dish for that wavelength. And having two antennas the same means manufacturing is more straight forward.....not only that, but two together joined at top and bottom is less likely to blow over in the wind.
A yagi would be another idea.....but can you imagine suspending the parasitic elements up there in the sky?.....better just make two the same and shove them together.
- Thread starter
- #6
This is what this guy I know said about your idea......
I don't think so, phased verticals are common but are spaced much farther than that to get the desired pattern, typically Lambda/4. They can be electrically phased with delay lines, but will need to be farther apart than that and certainly not electrically connected at the top.
Also, the guy wires don't have any insulators spread out to break up their resonances and the towers are too tall to use phillistran or other non-conductive guying material.
Plus, isn't that a vertical antenna on the top of the right-hand tower? No way the tower is being used as an antenna then. Is the base insulated or a feedpoint tapped up the side? Can't tell.
The area is way too arid for a vertical antenna, the grounding system would have to be extreme for high power AM broadcast, that's why they put them in low-lying, swampy areas for ground conductivity (and the land is cheap, too).
I showed this to two broadcast engineers who said it appeared to be a very wierd support tower for antennas, possibly antennas not yet installed.
I personally can tell you what I think it's NOT, but I don't know what it is.
My antennas are all wire phased arrays hanging from trees. They don't look like much, but I win a lot of contests and bust a lot of pileups with them.
I don't think so, phased verticals are common but are spaced much farther than that to get the desired pattern, typically Lambda/4. They can be electrically phased with delay lines, but will need to be farther apart than that and certainly not electrically connected at the top.
Also, the guy wires don't have any insulators spread out to break up their resonances and the towers are too tall to use phillistran or other non-conductive guying material.
Plus, isn't that a vertical antenna on the top of the right-hand tower? No way the tower is being used as an antenna then. Is the base insulated or a feedpoint tapped up the side? Can't tell.
The area is way too arid for a vertical antenna, the grounding system would have to be extreme for high power AM broadcast, that's why they put them in low-lying, swampy areas for ground conductivity (and the land is cheap, too).
I showed this to two broadcast engineers who said it appeared to be a very wierd support tower for antennas, possibly antennas not yet installed.
I personally can tell you what I think it's NOT, but I don't know what it is.
My antennas are all wire phased arrays hanging from trees. They don't look like much, but I win a lot of contests and bust a lot of pileups with them.
- Thread starter
- #7
Looks like a VLF antenna... Seen a few of them used in WW1 to receive and tx with submarines... That was before sky waves were used... Got a similar structure in Canberra, Australia and I think Sweden...
Could operate at powers of up to 140MW! I think...
They're no longer used commonly now days though.
Could operate at powers of up to 140MW! I think...
They're no longer used commonly now days though.
Looking at it, I wonder if this was originally a tower for a land microwave link. Two back-to-back dish antennas would have been mounted. The double tower construction is to keep high wind gusts from axially flexing the tower resulting in the antenna beam missing the next tower.
Microwave land-link comminications dissappeared and were replaced by satellites some time back.
The one antenna at the top appears to be a standard VHF array for a mobile service - probably a reuse of the tower once the original purpose became obsolete.
Microwave land-link comminications dissappeared and were replaced by satellites some time back.
The one antenna at the top appears to be a standard VHF array for a mobile service - probably a reuse of the tower once the original purpose became obsolete.
- Thread starter
- #10
The VLF antennas in Australia are higher than 100m though, like 300-400m plus an array of surrounding masts to carry the huge top-hat. Quite a few tons of buried copper too to improve ground resistance. Is this one in the photo a broad-band HF antenna. I cannot tell if the guys are active or not from the photo and the cross wires are interesting.
The radial at the top looks about 10 feet tall monopole. That's around 50 Mhz. To raise it that far, it might be an FM radio or TV channel 3 antenna, I hear they are making TV and FM broadcasts circular polarization lately. Could be a ham radio too.
It could also be a cow tracker. The beef industry is putting antennas in cow's ears and sending data about their health and location to central points. I'd bet on the radio or TV station though, looks too expensive and large for cows.
kevin.
It could also be a cow tracker. The beef industry is putting antennas in cow's ears and sending data about their health and location to central points. I'd bet on the radio or TV station though, looks too expensive and large for cows.
kevin.
robertjo24
Industrial
The tower is for high wind, ice/snow resistance. The antenna on top actually seems to be a uhf folded dipole antenna. I have seen these in Wyoming; we have a 900 MHZ MAS repeater on one.
This structure is way too small to come close to a VLF antenna.
BrianR is correct; the one in Australia, (Cape of Exmouth) is huge. The center tower was the tallest structure in the southern hemisphere for a long time. I used to be stationed there when it was a joint command and spent many days walking the antenna farm there.
The antenna is actually made up of large triangular shaped panels of steel cables strung from the center tower out like a flower. You can still see the footprint on Google Earth.
They would lower panels for maintenance, and we would have 50 guys out there moving barrels around so the cables wouldn't lie on the ground.
This structure is way too small to come close to a VLF antenna.
BrianR is correct; the one in Australia, (Cape of Exmouth) is huge. The center tower was the tallest structure in the southern hemisphere for a long time. I used to be stationed there when it was a joint command and spent many days walking the antenna farm there.
The antenna is actually made up of large triangular shaped panels of steel cables strung from the center tower out like a flower. You can still see the footprint on Google Earth.
They would lower panels for maintenance, and we would have 50 guys out there moving barrels around so the cables wouldn't lie on the ground.
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