"Signals" The NAAPO Newsletter Volume 18, No. 2; July 2002

Written by: Phil Barnhart, NAAPO Coordinator, 4655 Indian Ct., Westerville, OH 43082 Printer-Friendly Version

Editor's Comment The material contained in this issue of Signals was written during the month of July 2002. It will be evident (should you choose to read it) that some rather earth-shaking events [pun intended] transpired in the weeks leading up to the writing. I am solely responsible for the long gap in communication with our friends. I hope to be forgiven for not keeping everyone posted on the progress of the volunteers that make this operation go.

Coordinator's Corner    Phil Barnhart As this is being written (7/21/2002) I am literally cowering in the corner of a room at the Village of Westerville Rehabilitation and Convalescent Center. Just 18 days ago I tripped on a construction warning fence and did considerable mischief to my left femur. Details of how I was scraped from the sidewalk of the Ohio State University, shipped by a City of Columbus Emergency Squad to an off-campus hospital, endured a 22 hour pain-filled wait for a 4th of July surgery (the fireworks were not yet set up in the OR) and my subsequent road back to full recovery will undoubtedly be covered in an article in the New England Journal of Surgeon's Yachting. I can assure those of you who are hearing this for the first time that the prognosis is good, my spirits are less pain ridden and I have learned several techniques for relieving the effects of very active kidneys. What I immediately miss has been electronic contact - even one way - with the NAAPO projects. Jerry, Bob and Tom have kept the telephone lines to my room warm with progress reports, questions and condolences. The food that I manage to eat is reminiscent of a Neanderthal diet. Physical therapy approaches medieval torture chamber activities and nurses seem to take great delight in poking needles into me early and often. It looks like home in a week, a walker for another month, then a cane and the wheel of my politically incorrect SUV. I should be back on line for e-mail and electronic communication by August 1. Thanks to all who have bolstered my flagging spirits the past three weeks. I can see progress and recovery ahead and will be back to the working sessions by my birthday in September. Never again will I wish my theatrical friends to . . "break a leg!".

Noted in Passing . . . January 2002 marked the passing of one of the great pioneers of Radio Astronomy. Robert Hanbury Brown died, a victim of cancer at age 85. In 1936 Hanbury Brown was one of the early team members Henry Tizard recruited to Bawdsey Manor to develop radar. He spent 1942 through 1947 in Washington, D. C. and was responsible for sharing the British developments with the United States Navy in implementing both shipboard and airborne radar. After the war Hanbury returned to England and in 1949 joined the team at Jodrell Bank where with Cyril Hazard he turned Bernard Lovell's 218-foot reflector into a first class radio telescope. He is perhaps best known for his invention of the intensity interferometer. At radio frequencies the intensities are compared at two different antennas and the corresponding correlation is easily understood. At optical wavelengths this correlation translated into comparing the time of arrival of photons at the different collectors. Classical optics denied the possibility of such a measurement being made. The authority of the physicists was overthrown only when Hanbury Brown and Richard Twiss set up two surplus searchlight mirrors and measured the radius of Sirius. In so doing Hanbury Brown stimulated the formation of the new field of Quantum Optics. One result of Hanbury Brown's work with the intensity interferometer was to measure the angular size (thereby, along with knowing the distance, the radius) of 32 main sequence stars. This allowed the first wholly empirical determination of the temperature scale for hot stars. This represented a major accomplishment in fundamental astrophysics. Because of his activities during the early decades of the founding of radio astronomy, his adaptation of intensity interferometry to optical astronomy and the impetus this gave to the founding of quantum optics, it has been suggested that Hanbury Brown will remain one of the most regretted omissions by the Nobel Prize Committee.

Onward, Argus We have spent a slow six months in getting the next 8 elements of the Argus Array constructed. Early on many of us were learning the ropes in just how to fabricate the various elements of the initial design. Al Horton cut and arranged for the machining of 1/2 inch pressed wood boards for the weatherproof housings. Ange Campanella, Jerry Ehman, Bob Dixon and Phil Barnhart set up a gluing Assembly line that combined assembly and clamping in one operation. This was made possible by the precise jointing work done in cutting the pieces. Barnhart experimented with hand cutting the ground planes and internal reflectors. Even with thicknesses under that specified for the parts the cutting was slow and rough on hands and muscles. Extensive testing with a variety of glue, epoxy and contact cement led to selection of water activated polyurethane glue. It is more expensive but seems to result in overall stronger internal structural joints than the others. Painting of the enclosures was carried out in two sessions by Avis Needham (3rd grade) and Ashley Walker (7th grade) both happy to volunteer on the project. Final assembly, except for the spiral antennas and internal electronics, has been completed. These items are to be provided by Steve Ellingson.

Argus Construction; Phase Two The Miracle of Randy As the first 8 NAAPO assembled antenna boxes were nearing completion and a feeling of deep gloom settled around the possibility of hand cutting ANY number of ground planes and internal reflectors, a new volunteer appeared on the scene. Like a knight in shining armor with an arsenal of magnificent tools combined with an enthusiasm and talent unmatched in the annals of NAAPO volunteer recruiting, Randy Bixler arrived at a Saturday working session and announced "I can cut all of those metal and plastic shapes in no time at all!" This was a most welcome declaration to the hand- and arm-weary Phase I metal fabricators. Randy further allowed he could gain access to a stockpile of scrap aluminum in virtually any quantity we could want. Needless to say we offered Randy the opportunity to show us his stuff. Two weeks later he came to the meeting a little flustered. He told us eariler in the week he had cut 50 each (following our request for a demonstration of 8 each) of the three different elements. When he went to pick them up on the way to the meeting he discovered the janitor in his shop thinking they were scrap had thrown them out! Being used to various setbacks we were willing to grant him another two weeks to present his accomplishment. However, Randy informed us he had redone the job that morning and had the 50 (!) each with him that morning. He even apologized that they were not de-burred as the others had been. As a result, the time consuming really tough part of the fabrication of the reflector/ground plane assembly was reduced to a nearly trivial activity. This is truly a monumental accomplishment by a fresh, ambitious volunteer. To paraphrase Winston Churchill, "Never has so much benn done so easily through skill and drive . . . " We now have a goal to try to keep up with the rest of the Argus enclosure construction project.

Experiments Needed Fabrication of the next generation of Argus antenna elements may need an alternative to the pressed wood structural fabrication. Suggestions have floated for some time that a plastic structure might serve just as well. We know from our efforts to build conical spirals that polystyrene sheet seems transparent to microwaves. We need to perform similar tests on other plastic samples especially if we can find inexpensive surplus raw material. The idea of a transparent box or two has been brought up. Raw material cost has slowed us in this direction, but it may be a good PR statement for visitors wishing to see what the internal structure of the Argus element looks like.

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