"Signals" The NAAPO Newsletter Volume 22, No. 1 April 2006

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

CONSTRUCTION PROJECT PROGRESS In January the decision was taken to proceed on construction of 10 more elements for the Argus Array. This would involve building ten more digital receivers, ten more front-end LNAs and ten more spiral antenna elements. It will also fill out the 32 available slots in the receiver rack. Parts were ordered for the receivers and Phil Covington took on the assembly task. He has essentially completed all the assembly work. Testing of the new individual receivers will proceed upon delivery to the Satcom lab. Parts for the LNAs are on hand (except for the SNA connectors — back-ordered into April) and Ange Campanella is coordinating the assembly process. Ange also has repaired a spare LNA which is now ready for testing. Fabrication of the antenna elements is scheduled to begin within the next few weeks. The new elements should be ready for installation by early summer.

VOLUNTEERS LOCKED OUT OF FIRST MARCH MEETING Repair crews hired by the University installed a 'foreign' padlock on the driveway gate isolating the two authorized padlocks from the gate security chain. This necessitated a hike of from ¼ to ½ mile for the volunteers at the first March working session. Considerable grumbling was evidenced during the meeting. Bob Dixon made a discrete phone call on the Monday following which cleared up the situation, much to the relief of the foot-weary volunteers.

NEW EVIDENCE FOR “INTERESTING” EVENTS OPENS A NEW SEARCH OF THE BIG EAR ARCHIVES Announcement from Australia’s Parkes Radio Observatory in a recent Nature journal article of the detection of repeating short bursts of radio emission from some neutron stars has opened the possibility that some spike signals in Big Ear data might in fact be the result of such outbursts in the past. These typically were discounted as RFI in the original data sets and thus totally disregarded. With the archiving of much of the Big Ear data it now becomes possible to re-examine these runs for candidates for such spike bursts. Russ Childers has prepared a program to display successive day’s scans of the sky for the occurrence of short bursts in either horn. It will take a considerable expenditure of time to sift through the available data looking for repeated bursts in the same sky locations. Russ’s archive will be available on line so this will provide some remote volunteers the opportunity to engage in some important data sifting. Here is an example of a typical display: [Click on the image for a larger version.] Anyone interested in pursuing this activity should try to get to a working session for a complete training course. Russ is an outstanding mentor and this project provides a potential for very meaningful discovery.

ARGUS DETECTS (BUT DOES NOT LOCATE) HORRIBLE 1420 MHz NOISE SOURCE Observations on several occasions have disclosed very strong rfi (radio frequency interference) in the region surrounding the 1420 MHz protected frequency band. Its origin is unknown and Argus has been unable to obtain a direction for the source so it has become a worrisome event. It sometimes seems to rapidly drift to higher frequency before disappearing. At other times it persists for minutes at a time. We are very concerned not only because this is a 'protected' frequency, but it also interferes with the task at hand with the Argus Array. Two samples of the very strong interference are illustrated below. [Click on each image for a larger version.]

ANOTHER REMARKABLE SATELLITE DETECTION A satellite identification project is again becoming high on the priority list. A switch in frequency away from the 1420 MHz band to 1660 MHz caught the following satellite signature. [Click on the image for a larger version.] This flyby is remarkable in that there are more than one side-lobes present. Why the side-lobes did not appear on the display before the satellite center frequency entered the waterfall display is not clear. A catalog of available satellites and their transmitting frequencies would be very helpful.

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