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Rotatable couplings?
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? Clearly there would have to be some mechanical support other than just the co-axial coupling to withstand the wind storms that we are all now experiencing? |
Rotatable couplings?
On 1/30/2016 6:04 AM, 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? Clearly there would have to be some mechanical support other than just the co-axial coupling to withstand the wind storms that we are all now experiencing? Rotary Transformer These will keep you occupied for a while. http://coefs.uncc.edu/mnoras/files/2...Chapter_19.pdf https://www.pes.ee.ethz.ch/uploads/t...r_APEC2013.pdf http://www.fdk.co.jp/cyber-e/pdf/RT-RTE001.pdf Mikek |
Rotatable couplings?
"amdx" wrote in message
... On 1/30/2016 6:04 AM, 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? Clearly there would have to be some mechanical support other than just the co-axial coupling to withstand the wind storms that we are all now experiencing? Rotary Transformer These will keep you occupied for a while. http://coefs.uncc.edu/mnoras/files/2...Chapter_19.pdf https://www.pes.ee.ethz.ch/uploads/t...r_APEC2013.pdf http://www.fdk.co.jp/cyber-e/pdf/RT-RTE001.pdf Ta, but not what I had in mind, which was a rotary co-axial joint |
Rotatable couplings?
On 1/30/2016 9:51 AM, gareth wrote:
"amdx" wrote in message ... On 1/30/2016 6:04 AM, 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? Clearly there would have to be some mechanical support other than just the co-axial coupling to withstand the wind storms that we are all now experiencing? Rotary Transformer These will keep you occupied for a while. http://coefs.uncc.edu/mnoras/files/2...Chapter_19.pdf https://www.pes.ee.ethz.ch/uploads/t...r_APEC2013.pdf http://www.fdk.co.jp/cyber-e/pdf/RT-RTE001.pdf Ta, but not what I had in mind, which was a rotary co-axial joint http://www.macartney.com/what-we-off...50-and-75-ohm/ http://www.schleifring.com/ship-radar/ https://www.asianproducts.com/produc...ings-meet.html http://www.moog.com/literature/MCG/AC6355DS.pdf http://www.moog.com/products/slip-ri...psules/ac6305/ http://www.slipring.com/series-high-...-273-l-en.html Power levels could be a problem. |
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 |
Rotatable couplings?
|
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 |
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 |
Rotatable couplings?
On Sat, 30 Jan 2016 12:04:49 -0000, "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? Clearly there would have to be some mechanical support other than just the co-axial coupling to withstand the wind storms that we are all now experiencing? "Slip rings". https://www.google.com/search?q=slip+ring&tbm=isch https://www.google.com/search?q=coaxial+slip+ring&tbm=isch For coax cables, it's a "rotary joint". https://www.google.com/search?tbm=isch&q=rf+rotary+joint I like to use a balun to go from coax to a parallel transmission line, then to slip rings, and then to a dipole antenna feed. I once built a direction finder that used a rotating yagi antenna, using that method. As amdx mentioned, RF power levels are going to be a problem. My interest is in direction finders, which normally do not transmit. If you're going to run RF through the rotary joint while rotating the antenna, the RF is going to arc and burn a nice neat groove in the contact area. If the rotary joint is locked in place, it might survive at low power levels. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
Rotatable couplings?
On Sat, 30 Jan 2016 18:24:02 -0000, wrote:
Sounds like a $200 solution to a $0.75 problem, i.e. an extra foot or two of coax to allow slack for turning. Long ago, I had what I thought was a good idea. I was working for a marine radio manufacturer. Getting decent range with 25 watts into an omni antenna was problematic in some areas. What worked was a directional yagi with lots of gain. The problem was how and where to aim it. Since I was working on an ADF (automatic direction finder) at the time, that displayed the direction as 0 to 359 degrees, I thought that coupling the display to a rotator would be a good idea. The problem was the conventional TV or ham antenna rotator didn't turn fast enough to switch direction among multiple stations. So, I installed a rotary joint which allowed swinging the yagi quite rapidly. The rest was a tangle of junk made from a servo, shaft encoder, discrete logic, and the usual spaghetti wiring. I switching to 2 meters for testing. The results were ummm... interesting. The direction finder output was not very stable, so the antenna liked to vibrate and jitter over about a 15 degree swing. If the station it was tracking crossed over 0 degrees, the antenna would swing all the way around to get to the other side (logic error). A fast back and forth QSO would result in the antenna doing a "wind vane" simulation. Management was thoroughly irritated by the noise it made on the roof, which could be heard everywhere in the building. The consensus among the other engineers was that this was a truly stupid idea. I wanted to continue, but testing was terminated when the mast bent at the rotary joint and someone sabotaged the interface breadboard. Anyway, an extra long service loop would not have worked for this project. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
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 |
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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