The Radio Meteor Project: First Radio System Test

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First Radio System Test

A big meteor shower is an excellent time to test the new meteor radio system, and the November Leonid meteor shower which was about to peak, provided that opportunity. The specific observation frequency for the initial test needed to be selected before designing the antenna. The TV4 (67.25 MHz) signal used in the NASA program was unsuitable because of NJAA's close proximity to both the New York and Philadelphia broadcast areas. The only unused broadcast TV channel in this area appeared to be channel 8 (181.25 MHz). There was some question as to it's appropriateness for test purposes because according to the literature: the received signal strength is proportional to the cube of the wavelength. This means that the higher frequency would likely provide only short and weak echoes. However, due to the narrow time window for a first test during a period of high meteor activity, a decision was made to proceed without over-postulating the design.

First, an antenna needed to be constructed. The design in the NASA system is simple and inexpensive to build.

If it proved unworkable, it was easily scrapped for a "Plan B" alternative. So, on the Sunday afternoon before Leonids, an antenna quickly took shape. It incorporated the design formula of the NASA system, with the antenna dimensions altered for the chosen frequency.

After verifying that it received the local television frequencies quite well, it was tuned to the TV channel 8 video frequency. Interspaced amid the steady sound of static were a number of short lived tonal changes. However, no determination could be made if meteors or some other source caused the distinctive sounds. Further, nothing could be determined by the spectrum analyzer incorporated in the software interface of the radio receiver.

In order to confirm that the system was actually detecting meteors, a method of matching the captured echoes with the video data was necessary. Subsequently, the next test of the system called for the incorporation of specialized software to accumulate the radio data. Software that created a time stamped record of events was the needed make a comparison between the two platforms. This would allow for the comparison of the captured meteor echoes with the all-sky camera results. Since the computers now had an accurately synchronized time, there would be little question if both results matched.

Radio meteor observing is very popular in both Japan and Europe, and there are many foreign language Websites on the subject. A software program called Ham Radio Observational Fast Fourier Transform (HROFFT) developed by Kazuhiko Ohkawa, appeared to be one of the most popular in use.

The explanatory web pages for this software are available on Japanese sites like http://www.amro-net.jp/analyze.htm, which covers the analyzing of observational data, but lack a direct link to the actual software. However, the French language site http://radio.meteor.free.fr/fr/index.php?p=logiciels, contains the program, but instruction that accompany the software are in French. Google's translator feature managed to glean some of the initial setup information about the HROFFT program, as there is very little of it available elsewhere. Since the radio receiver must provide a specific audio input to the HROFFT software, some useful information about setting the parameters on the radio receiver was located on http://www.spaceweather.com/glossary/nasameteorradar.html where Dr. Sugg suggested using the CW demodulator setting, with the IR filter set to a 3 kHz bandwidth, and adjusting the IF-shift to minimize interference signal level. This recommendation closely matched the screen shot of the IC-PCR1500 receiver depicted on the French site.

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