[amsat-bb] Re: 70 MPH S-band dish

[Bob Bruninga]

> 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?

Bob, WB4APR