Hi Kim, I was thinking a bit more about the cylindrical parabaloid and a few synapses finally started to fire... I believe at the focus of the parabola you have basically a single dipole antenna? My understanding is that the dipole needs to be an odd number of half-wavelengths in size. This would basically be a hybrid and I think would have some of the advantages/disadvantages of the other types. Advantages: Aperture - as you mentioned you could build a good sized antenna using some plywood and mesh or screen Price - Very cheap to build and you could use scraps from other projects Disadvantages: Noise rejection - Since your feed is a single dipole I think you would get a lot of off axis noise. Bulkiness - It would probably get fairly heavy if the length was much more than a meter. I remember now that back in high school there was a kid at the regional science fair (at Weber State) that built a cylindrical parabolic radio telescope. (He probably stole your idea since this was 1977 <g>). He covered the parabolic surface with aluminum foil. He said it worked pretty well but I didn't know enough to ask any good questions. As I recall it was obviously movable but was probably more semi-portable. Clear skies, Dale.
...snip... I finally determined to build a Yagi array, but not before I realized that a cylindrical parabaloid would have also been very easy to build and with very little skill or exotic materials required. I don't recall why I settled on the Yagi array, I have simply forgotten too much of the physics involved. And that finally brings me to a question I have for you and others: What would be the advantages/disadvantages of one type of antenna over another? I would still rule out the conventional parabolic dish because of the relative complexity of its construction for a basement tinkerer like me. However, the cylindrical parabaloid is still quite easy to construct with some plywood, a simple plot of a parabola on a piece of paper for a pattern, and some hardware fabric or insect screen to cover the surface. Can anyone enlighten me? Remember, you need to explain in terms my few remaining viable brain cells can comprehend.
Thanks all.