[amsat-bb] Re: 70 MPH S-band dish
bruninga at usna.edu
Sat Oct 29 11:43:25 PDT 2011
> Bob, You might want to consider a Helical antenna
> for your mobile station. It would have less wind
> drag and easier to rotate.
Actually, I'm beginning to think we will build our own dish. I have a 5' solid metal dish. I think we will just use it as a form and lay in some copper strips evry 4 inches or so in one dimension, then overlay say, #12 copper wire every 1" in the other direction, and then solder each crossover point.
The result will be a linear polarized 4' dish with very low aerodynamic crossection. A little structure behind it and is it should handle 70 MPH easily.
I think 1/4" wide copper strap is used for winding some big motors, and should be easy to find. Using the flat strap for the supports gives a nice soldering cross point.
We need the 4' dish to close the link when the balloon is 20 miles up. I dont think we can get that with a helix. My guess is the dish will give us about 24 dBi vertically polarized with a beamwidth of about 10 degrees?
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