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A method and apparatus for communicating simultaneously at the same frequencies includes two or more conductor-backed, spiral antennas that have been shown to exhibit linear polarization. To permit simultaneous transmission on the same frequencies, two of the linearly polarize, conductor-backed spir

A method and apparatus for communicating simultaneously at the same frequencies includes two or more conductor-backed, spiral antennas that have been shown to exhibit linear polarization. To permit simultaneous transmission on the same frequencies, two of the linearly polarize, conductor-backed spiral antennas can be spaced vertically and be oriented so that the feed points of one antenna are orthogonal to the feed points of the second antenna. Since the specifically designed spiral antennas will be both transmitting or both receiving at orthogonally arranged polarizations, the antennas will not interfere with each other, even though communication is upon substantially the same frequencies.

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What is claimed is: 1. An antenna apparatus comprising: first and second linearly-polarized conductor-backed spiral antennas wherein said antennas both simultaneously transmit or both simultaneously receive on substantially the same frequencies, wherein said antennas are spaced from each other and

What is claimed is: 1. An antenna apparatus comprising: first and second linearly-polarized conductor-backed spiral antennas wherein said antennas both simultaneously transmit or both simultaneously receive on substantially the same frequencies, wherein said antennas are spaced from each other and further wherein each of said antennas comprises: a substrate having first and second flat, opposite, sides; a pair of spiral antenna elements disposed on said first side of said substrate in which each of said elements has a corresponding feed point; and a conducting ground plane disposed on said second side of said substrate, wherein said first antenna and said second antenna are oriented so that an imaginary line drawn through said feed points corresponding to said first antenna is orthogonal to an imaginary line drawn through said feed points corresponding to said second antenna. 2. The apparatus of claim 1 wherein said antennas are spaced vertically to radiate substantially parallel. 3. The apparatus of claim 1 in which said spiral elements take the form of an Archimedean spiral. 4. The apparatus of claim 1 wherein said spiral elements comprise a metal foil. 5. The apparatus of claim 1 wherein said antenna elements of said first and second antennas are mounted in a common plane. 6. The apparatus of claim 1 wherein said substrate has a dielectric constant of approximately 1. 7. The apparatus of claim 6 wherein said substrate comprises a dielectric of DIVINYCELL (trademark). 8. The apparatus of claim 1 wherein said first and second antennas share a common conducting ground plane. 9. An antenna apparatus comprising: first and second linearly-polarized conductor-backed spiral antennas wherein said antennas both simultaneously transmit or both simultaneously receive on substantially the same frequencies, wherein said antennas are spaced from each other and further wherein each of said antennas comprises: a substrate having first and second flat, opposite, sides; a pair of spiral antenna elements disposed on said first side of said substrate in which each of said elements has a corresponding feed point; and a conducting ground plane disposed on said second side of said substrate, wherein said first antenna and said second antenna are oriented so that an imaginary line drawn through said feed points corresponding to said first antenna does not coincide with an imaginary line drawn through said feed points corresponding to said second antenna and wherein the performance of each of said antennas can be described by an axial ratio defined as the difference between vertical gain and horizontal gain at a particular frequency and wherein said axial ratio varies by no less than plus or minus 5 dB. 10. The apparatus of claim 9 wherein said spiral antenna elements makes at least three 360 degree turns. 11. The apparatus of claim 10 wherein said substrate separates said spiral antenna elements from said conducting ground plane by a distance that is no greater than 6 inches. 12. The apparatus of claim 11 wherein said imaginary line drawn through said feed points corresponding to said first antenna is orthogonal to said imaginary line drawn through said feed points corresponding to said second antenna. 13. The apparatus according to claim 11 wherein said antennas operate between 225 megaHertz and 400 megaHertz. 14. The apparatus of claim 10 wherein said substrate separates said spiral antenna elements and said conducting ground plane by a distance that is no greater than 3 inches. 15. The apparatus of claim 14 wherein said imaginary line drawn through said feed points corresponding to said first antenna is orthogonal to said imaginary line drawn through said feed points corresponding to said second antenna. 16. The apparatus of claim 14 wherein said antennas operate between 225 megaHertz and 400 megaHertz. 17. The apparatus of claim 10 wherein said substrate separates said spiral antenna elements and said conducting ground plane by a distance that is no greater than 1 inch. 18. The apparatus of claim 17 wherein said imaginary line drawn through said feed points corresponding to said first antenna is orthogonal to said imaginary line drawn through said feed points corresponding to said second antenna. 19. The apparatus of claim 17 wherein said antennas operate between 225 megaHertz and 400 megaHertz. 20. An antenna apparatus comprising: first and second linearly-polarized conductor-backed spiral antennas wherein said antennas both simultaneously transmit or both simultaneously receive on substantially the same frequencies, wherein said antennas are spaced from each other and further wherein each of said antennas comprises: a substrate having first and second flat, opposite, sides; a pair of spiral antenna elements disposed on said first side of said substrate in which each of said elements has a corresponding feed point, said spiral antenna elements making at least three 360 degree turns; and a conducting ground plane disposed on said second side of said substrate, wherein said substrate separates said spiral antenna elements from said conducting ground plane by a distance that is no greater than 6 inches, wherein said first antenna and said second antenna are oriented so that an imaginary line drawn through said feed points corresponding to said first antenna is orthogonal to an imaginary line drawn through said feed points corresponding to said second antenna. 21. The apparatus of claim 20 wherein said antennas are spaced vertically. 22. The apparatus of claim 20 in which said spiral takes the form of an Archimedean spiral. 23. The apparatus of claim 20 wherein said spiral elements comprise a metal foil. 24. The apparatus of claim 20 wherein said antenna elements of said first and second antennas are mounted in a common plane. 25. The apparatus of claim 20 wherein said substrate has a dielectric constant of approximately 1. 26. The apparatus of claim 25 herein said substrate comprises a dielectric of DIVINYCELL (trademark). 27. The apparatus of claim 20 wherein said first and second antennas share a common conducting ground plane. 28. The apparatus according to claim 20 wherein said antennas operate between 225 megaHertz and 400 megaHertz. 29. The apparatus of claim 20 wherein said substrate separates said spiral antenna elements and said conducting ground plane by a distance that is no greater than 3 inches. 30. The apparatus of claim 29 wherein said antennas operate between 225 megaHertz and 400 megaHertz. 31. The apparatus of claim 20 wherein said substrate separates said spiral antenna elements and said conducting ground plane by a distance that is no greater than 1 inch. 32. The apparatus of claim 31 wherein said antennas operate between 225 megaHertz and 400 megaHertz. 33. A communications method comprising: using first and second linearly polarized, conductor-backed spiral antennas to both simultaneously transmit or both simultaneously receive on substantially the same frequencies, wherein said antennas are spaced from each other and further wherein each of said antennas comprises: a substrate with first and second flat, opposite, sides; a pair of spiral antenna elements disposed on said first side of said substrate in which each of said elements has a corresponding feed point, said spiral antenna elements making at least three 360 degree turns; and a conducting ground plane disposed on said second side of said substrate, wherein said substrate separates said spiral antenna elements from said conducting ground plane by a distance that is no greater than 6 inches, wherein said first antenna and said second antenna are oriented so that an imaginary line drawn through said feed points corresponding to said first antenna does not coincide with an imaginary line drawn through said feed points corresponding to said second antenna. 34. The method of claim 33 wherein said antennas are oriented so that said imaginary line drawn through said feed points corresponding to said first antenna is orthogonal to said imaginary line drawn through said feed points corresponding to said second antenna. 35. The method of claim 34 wherein said antennas are spaced vertically. 36. The method of claim 33 wherein said antenna elements of said first and second antennas are mounted in a common plane. 37. The method of claim 33 wherein said first and second antennas are included in a first antenna array and further wherein duplicates of said first and second antennas are included in a second antenna array. 38. The method according to claim 37 wherein said first and second antenna arrays are used for transmitting and receiving communication on substantially the same frequencies wherein one of said arrays is used for transmitting and the other of said arrays is used for receiving. 39. The method of claim 34 wherein said first and second antennas are included in a first antenna array and further wherein duplicates of said first and second antennas are included in a second antenna array. 40. The method according to claim 38 wherein said first and second antenna arrays are used for transmitting and receiving communication on substantially the same frequencies wherein one of said arrays is used for transmitting and the other of said arrays is used for receiving. 41. The method according to claim 33 wherein said antennas are operated between 225 megaHertz and 400 megaHertz. 42. The method of claim 33 wherein said substrate separates said spiral antenna elements and said conducting ground plane by a distance that is no greater than 3 inches. 43. The method of claim 42 wherein said antennas operate between 225 megaHertz and 400 megaHertz. 44. The method of claim 33 wherein said substrate separates said spiral antenna elements and said conducting ground plane by a distance that is no greater than 1 inch. 45. The method of claim 44 wherein said antennas operate between 225 megaHertz and 400 megaHertz.