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#1
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Rotatable couplings?
gareth wrote:
One of the problems with beams is the cable winding around the mast if you try to turn too far in one way or another. These difficulties have long been solved in the world of radar, so, has anyone conceived of an infinitely rotatable 50 ohm coupling for our beam antennae? Sounds like a $200 solution to a $0.75 problem, i.e. an extra foot or two of coax to allow slack for turning. -- Jim Pennino |
#2
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Rotatable couplings?
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#3
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Rotatable couplings?
"rickman" wrote in message ... On 1/30/2016 1:24 PM, wrote: gareth wrote: One of the problems with beams is the cable winding around the mast if you try to turn too far in one way or another. These difficulties have long been solved in the world of radar, so, has anyone conceived of an infinitely rotatable 50 ohm coupling for our beam antennae? Sounds like a $200 solution to a $0.75 problem, i.e. an extra foot or two of coax to allow slack for turning. I think the issue is that you have to manage the turning so you don't go too far in either direction before reversing. Most ham rotators will not go much over 1 turn. Some will go about 1 and a half. If you offset the coax about half a turn it does not have to flex all that much. That is if the beam stops to the north, turn the beam south and tape the coax to the mast and then go to the other side of the tower and tape the coax there. Be sure to leave plenty of coax for the antenna to turn. |
#4
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Rotatable couplings?
rickman wrote:
On 1/30/2016 1:24 PM, wrote: gareth wrote: One of the problems with beams is the cable winding around the mast if you try to turn too far in one way or another. These difficulties have long been solved in the world of radar, so, has anyone conceived of an infinitely rotatable 50 ohm coupling for our beam antennae? Sounds like a $200 solution to a $0.75 problem, i.e. an extra foot or two of coax to allow slack for turning. I think the issue is that you have to manage the turning so you don't go too far in either direction before reversing. Commercial rotators only turn +/- 180 degrees. If you are building your own, adding limit switches is far simpler, cheaper and more reliable than a rotary coupling. As the supply of WWII and Korean war prop pitch motors has pretty much dried up and they cost more than a used commrcial rotator ready to go, I don't see much motivation for building a rotator from scratch these days. -- Jim Pennino |
#5
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Rotatable couplings?
In rec.radio.amateur.antenna, you wrote:
gareth wrote: One of the problems with beams is the cable winding around the mast if you try to turn too far in one way or another. These difficulties have long been solved in the world of radar, so, has anyone conceived of an infinitely rotatable 50 ohm coupling for our beam antennae? Sounds like a $200 solution to a $0.75 problem, i.e. an extra foot or two of coax to allow slack for turning. With 4 different yagis on the mast, a large, bundled loop of coax(es) *HAS* to be The Way To Go. Jonesy W3DHJ -- Marvin L Jones | W3DHJ | W3DHJ | http://W3DHJ.net/ Pueblo, Colorado | @ | Jonesy | __ 38.238N 104.547W | jonz.net | DM78rf | 73 SK |
#6
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Rotatable couplings?
On Sat, 30 Jan 2016, Allodoxaphobia wrote:
In rec.radio.amateur.antenna, you wrote: gareth wrote: One of the problems with beams is the cable winding around the mast if you try to turn too far in one way or another. These difficulties have long been solved in the world of radar, so, has anyone conceived of an infinitely rotatable 50 ohm coupling for our beam antennae? Sounds like a $200 solution to a $0.75 problem, i.e. an extra foot or two of coax to allow slack for turning. With 4 different yagis on the mast, a large, bundled loop of coax(es) *HAS* to be The Way To Go. Yes, radar needed such couplings since the antenna went around 360 degrees, since you wanted to see in all directions. And I'd like to think they've now moved to "electronically steerable" arrays for radar, multiple fixed antennas that are switched to the receiver via diodes or whatever. You see some of that in amateur radio DF'ing. Michael |
#7
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Rotatable couplings?
Michael Black wrote:
On Sat, 30 Jan 2016, Allodoxaphobia wrote: In rec.radio.amateur.antenna, you wrote: gareth wrote: One of the problems with beams is the cable winding around the mast if you try to turn too far in one way or another. These difficulties have long been solved in the world of radar, so, has anyone conceived of an infinitely rotatable 50 ohm coupling for our beam antennae? Sounds like a $200 solution to a $0.75 problem, i.e. an extra foot or two of coax to allow slack for turning. With 4 different yagis on the mast, a large, bundled loop of coax(es) *HAS* to be The Way To Go. Yes, radar needed such couplings since the antenna went around 360 degrees, since you wanted to see in all directions. And I'd like to think they've now moved to "electronically steerable" arrays for radar, multiple fixed antennas that are switched to the receiver via diodes or whatever. You see some of that in amateur radio DF'ing. Michael They are called phased arrays; here are two I worked on: https://en.wikipedia.org/wiki/AN/TPQ...refinder_radar https://en.wikipedia.org/wiki/AN/TPQ...refinder_radar These use active electronically scanned arrays. A discussion of how it works: https://en.wikipedia.org/wiki/Phased_array https://en.wikipedia.org/wiki/Active..._scanned_array Phased arrays are extremely complex and expensive compared to simple rotating search radars. -- Jim Pennino |
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