"Spin-tenna" ?!
Conundrum, Mon Mar 24 2008, 03:37PMInteresting idea:-
Parabolic piece of high tensile springy wire mounted centrally on a brushless motor, with wifi dongle at effective focal point.
This may with sufficiently high rotary speed approximate a dish antenna without the annoying weight, bulk and other annoyances.
Additionally, it should also be possible to tune the focal point by adjusting motor speed.
Perhaps this could have applications for very lightweight antennae on model aircraft? (the assembly could be mounted horizontally
for optimal coverage)
Maybe also useful for mine detector applications?
-A
Re: "Spin-tenna" ?!
Proud Mary, Mon Mar 24 2008, 04:25PM
Don't you think your rotating piece of wire might look as though it were almost standing still compared with the speed of light?
Proud Mary, Mon Mar 24 2008, 04:25PM
Don't you think your rotating piece of wire might look as though it were almost standing still compared with the speed of light?
Re: "Spin-tenna" ?!
Conundrum, Mon Mar 24 2008, 04:47PM
Indeed- however a similar approach is used in microwave ovens in the form of a rapidly spinning "stirrer". in principle a flat metal sheet would work with relatively low rotational speeds.
Obviously there would be gaps, however for applications where you absolutely need a lightweight antenna it might provide some useful gain.
Google "plasma antenna" :)
Regards, -A
Conundrum, Mon Mar 24 2008, 04:47PM
Indeed- however a similar approach is used in microwave ovens in the form of a rapidly spinning "stirrer". in principle a flat metal sheet would work with relatively low rotational speeds.
Obviously there would be gaps, however for applications where you absolutely need a lightweight antenna it might provide some useful gain.
Google "plasma antenna" :)
Regards, -A
Re: "Spin-tenna" ?!
Proud Mary, Mon Mar 24 2008, 05:54PM
If you say so!
Proud Mary, Mon Mar 24 2008, 05:54PM
If you say so!
Re: "Spin-tenna" ?!
Dave Marshall, Mon Mar 24 2008, 07:16PM
The point of the spinning metal in a microwave is actually to scatter the beam. This minimizes hot spots within the microwave cavity. The same effect could be duplicated with any moving bit of metal, and the scattering effect isn't precise. It serves the same purpose as the moving turntable in a microwave.
I'd have to agree with Harry on this one. A best case result would be substantial scattering of the signal favoring a direction based on where the reflector was at any given time. Yes, some RF would likely be reflected in the direction you wanted, but a vast majority would continue on its merry way which ever direction it started out heading. I think a best case scenario would be a parasitic interaction between the radiator and the reflector (think Yagi) that would generate a somewhat directional, but distorted and constantly changing field.
Compare it to taking a thin strip of polished metal and spinning it in front of a light. Yeah, a little bit of light will be reflected, but the power needed to drive the motor would be much better spent just making the light brighter.
Dave
Dave Marshall, Mon Mar 24 2008, 07:16PM
The point of the spinning metal in a microwave is actually to scatter the beam. This minimizes hot spots within the microwave cavity. The same effect could be duplicated with any moving bit of metal, and the scattering effect isn't precise. It serves the same purpose as the moving turntable in a microwave.
I'd have to agree with Harry on this one. A best case result would be substantial scattering of the signal favoring a direction based on where the reflector was at any given time. Yes, some RF would likely be reflected in the direction you wanted, but a vast majority would continue on its merry way which ever direction it started out heading. I think a best case scenario would be a parasitic interaction between the radiator and the reflector (think Yagi) that would generate a somewhat directional, but distorted and constantly changing field.
Compare it to taking a thin strip of polished metal and spinning it in front of a light. Yeah, a little bit of light will be reflected, but the power needed to drive the motor would be much better spent just making the light brighter.
Dave
Re: "Spin-tenna" ?!
Alex, Mon Mar 24 2008, 07:20PM
Harry is right. You would have a wifi antenna pointing at a piece of wire that was moving around, perhaps scattering it slightly in random directions.
The spinning reflector in some microwaves is just used to move null regions and hot spots around to keep from burning your food in some places and freezing it in others. It provides no gain.
[edit] Damn, beat by 4 minutes.
Alex, Mon Mar 24 2008, 07:20PM
Harry is right. You would have a wifi antenna pointing at a piece of wire that was moving around, perhaps scattering it slightly in random directions.
The spinning reflector in some microwaves is just used to move null regions and hot spots around to keep from burning your food in some places and freezing it in others. It provides no gain.
[edit] Damn, beat by 4 minutes.
Re: "Spin-tenna" ?!
Conundrum, Wed Mar 26 2008, 07:55AM
Grr. Yeah, I just saw the horrible glaring error in my cunning plan.
That said, I had considered the possibility that a very coarse grained dish made of thin mesh in a vacuum, charged from a small Tesla coil might make a fairly good approximation of a plasma antenna...
Spinning it would not achieve very much at all, unless the intention here WAS to scatter radiation in all directions.
-A
Conundrum, Wed Mar 26 2008, 07:55AM
Grr. Yeah, I just saw the horrible glaring error in my cunning plan.
That said, I had considered the possibility that a very coarse grained dish made of thin mesh in a vacuum, charged from a small Tesla coil might make a fairly good approximation of a plasma antenna...
Spinning it would not achieve very much at all, unless the intention here WAS to scatter radiation in all directions.
-A
Print this page