I have been working on BANDA for about 4 weeks now. I have made a lot of progress, but there is still much to do.
What I have already done:
- Looked for information regarding bicone antennas and other related topics with Melvyl, World-Wide Web, Tecom Industries (tech support). I have also discussed this topic with many who know more than I both at LBL and across the country, in particular, George Frichter (University of Kansas) who is working on the same project from the theoretical side and Giovanni De Amici, the wise one.
- I have built two prototype antennas, experimenting with different conical half- angles.
- I have tested the reflectance of these two antennas using the laboratory test setup (frequency sweeper, network analyzer, directional bridge). The more desirable antenna, the 30° half-angle antenna, had maximum transmission in the 300 - 400 MHz range, close to the expected value of about 450 MHz.
- I have measured the field pattern of these two antennas on the roof. I did this using a dipole transmitting antenna design by Giovanni De Amici which I built myself. This was not quite as successful. I also had to build a mounting system out of PVC pipe for the antennas under test. Definitely more successful with the better antenna, but even though the field pattern somewhat resembled what we expected during one trial, it did not on the second trial. I am also questioning the stability of the signal power sent out by the RF generator. If it fluctuates over time, then our measurements are of little significance.
- I have drafted a design which will allow the antenna to attach onto the AMANDA cables, giving ample clearance and protection. I will use a 24" hollow tube of Lucite which will be sliced down the middle for easy mounting.
- I have began to consider what sort of circuitry will be used. And the pressure resistant vessels needed to store them it.
- I have corresponded with an EE at Tecom Industries, named Avi regarding our antenna design. He seems to think that the cable running along our antenna's axis of symmetry is a major problem. This cable is not entirely in the neglectable region of the field pattern for it runs right through the field pattern at its center. He has suggested a complicated way to make the antenna invisible to the cable.
I still need to:
- Look into this problem of the AMANDA cable interfering with our field patterns, redesigning the antenna if necessary.
- Finalize the antenna's dimensions, according to the central frequency we desire. I must not forget to take into account the refractive index of ice, 1.78.
- Discuss the circuitry/amplification with those more knowledgable. Decide on how all this will mount inside the antenna and how it will withstand the pressure.
- Build the three final antennas and prepare them to go to Antarctica.
- Run the necessary tests here to verify the functionability of the completed antennas.
- Consider what procedures to be performed once in Antarctica. Document them.
- Get information on BANDA onto a World Wide Web page.
There is a great deal of work to be done. I hope to complete this project by September 1, 1995, my date of departure. I am documenting my progress however, so that those who follow-up my work will know what I have done.
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