Re: inquiry about homebrew az-el systems
Samudra,
Most of us could probably cobble together some sort of one-of-a-kind design using surplus motors and gears from Skycraft or other sources. Making a design that is reproducible and publishable, made from parts and components that will be available in quantity a year or two or three from now is another matter.
I have experience making various antenna kludges for use on field day, with door hinges as elevation bearings, and ropes, pulleys and threaded rod as actuators. Everything but the motors came from Home Depot (but the small electric screwdrivers that they sell there could make great gear motors...) I never had any intention of leaving it up all year long or operating it unattended on a roof top. My design worked OK when the air was calm but the slightest breeze would back-drive the motors and blow it all over the place. When antennas start acting as sails in the wind, you need strong motors and big gear ratios, probably with brakes. You might perhaps take a look at the AlfaSpid design, which uses automobile windshield wiper motors to drive really big worm gears.
Practically speaking, you will need a better workshop than just a grinder, a drill, a saw and a few hand tools. A lathe and a small bench-top milling machine are essential to any serious metal worker. You might be able to find these at a local "maker" shop in your town if there is one, or look at www.littlemachineshop.com, $1500 should get you a basic bench top machine shop, about the cost of an all mode satellite radio.
Finally, Samudra, as a graduate student working on your PhD, is this really the best use of your time? In the end, that is the reason why most hams end up writing a check and buying a ready made rotor system, so they can get on to doing other things in their hobby and their life.
73 Dan Schultz, N8FGV
I would like to clarify: this antenna project is going to be handled by others ham operators who have contacted me. Where possible, I am contributing some hardware/mechanical parts that I have in stock. The work for the antenna is not for my Ph.D program. As I mentioned, it is for the K3GWU project which will go on in parallel, and there are others at GWU who will be involved. I have donated a lot of equipment to the K3GWU station, and that can go on to connect with an antenna when ready.
On the other hand, the ECE dept and MAE dept has resources (motors, gears) that they want to throw away ... and that they *have* to junk at some time after 5-10 years.
On Sun, Feb 24, 2013 at 10:43 PM, Daniel Schultz [email protected] wrote:
Samudra,
Most of us could probably cobble together some sort of one-of-a-kind design using surplus motors and gears from Skycraft or other sources. Making a design that is reproducible and publishable, made from parts and components that will be available in quantity a year or two or three from now is another matter.
I have experience making various antenna kludges for use on field day, with door hinges as elevation bearings, and ropes, pulleys and threaded rod as actuators. Everything but the motors came from Home Depot (but the small electric screwdrivers that they sell there could make great gear motors...) I never had any intention of leaving it up all year long or operating it unattended on a roof top. My design worked OK when the air was calm but the slightest breeze would back-drive the motors and blow it all over the place. When antennas start acting as sails in the wind, you need strong motors and big gear ratios, probably with brakes. You might perhaps take a look at the AlfaSpid design, which uses automobile windshield wiper motors to drive really big worm gears.
Practically speaking, you will need a better workshop than just a grinder, a drill, a saw and a few hand tools. A lathe and a small bench-top milling machine are essential to any serious metal worker. You might be able to find these at a local "maker" shop in your town if there is one, or look at www.littlemachineshop.com, $1500 should get you a basic bench top machine shop, about the cost of an all mode satellite radio.
Finally, Samudra, as a graduate student working on your PhD, is this really the best use of your time? In the end, that is the reason why most hams end up writing a check and buying a ready made rotor system, so they can get on to doing other things in their hobby and their life.
73 Dan Schultz, N8FGV
Gentlemen, Google is your friend here. I can kit a G-5500 class rotator from available shafts, bearings, gears, motors and such for less than $300. That's not accounting for economies of scale. Add some stuff from radio shack and the appropriate length of wire and you have for less than $500 a complete Az-El rotator and associated driving stuff, less antennas (which can be made reliably and cheeply) and antenna support.
A quick search on CL will yield a tower section reasonably. I got a bunch at $70 just a few months ago.
Step over from Skycraft to AES and see what they charge for this stuff.
The rotators sold now cannot be repaired, period. When the bit of kit on the top of my tower goes, I'll probably build one. Much cheaper that paying the 1500 that the top line mfgr wants for theirs..
I submit that the aformentioned project could be homebrewed by someone with a torch and access to a junkyard and tools no more complex than a grinder. The interface electronics are a little more difficult to build, but certainly wouldn't take a lathe.
Norm n3ykf
participants (3)
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Daniel Schultz -
Lizeth Norman -
Samudra Haque