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(meteorobs) Radio Detection of Albuquerque Fireball
Probable Radio Detection of Fireball West of Albuquerque:
Boslough and Spalding have recently reported a videotaped fireball
estimated to be 300 km west of Albuquerque on August 15 at 5:18 UT. The
radiometeor observatory at the Van Andel Creation Research Center near
Chino Valley, Arizona regularly detects about 3,000 meteors in a normal,
24 hour period. A retrospective examination of our radiometeor data shows
a
29 second over-dense FM forward scatter reflection starting at about
5:18:26 UT on that date.
The computer recording was triggered at -125 dBm and rose to at least -110
dBm within three seconds. The signal was characterized by the typical
heavily oscillating destructive and constructive interference patterns.
After 10 seconds it began to decay toward threshold levels.
The timing and nature of the forward scattered signal support the high
probability that the Albuquerque fireball produced the 29 second
reflection recorded at our radiometeor observatory.
Brief system specifications:
Antenna: A 1/2 wave dipole was located three feet above ground and backed
by 90 degree corner reflector made of chicken wire. The reflector was
facing east and the center was tilted at about 60 degrees above the
horizon. A 27 dB preamp at the antenna drove the signal into 500 feet of
coax leading to the receivers.
Receivers: Three Radio Shack STA-300 FM receivers were tuned to 88.5,
88.9, and 89.7 MHz. The receivers were modified to increase sensitivity,
to narrow bandwidth, and to measure signal strength. Typical commercial FM
stations to the east of the antenna on these frequencies are in
Texas.Oklahoma, Kansas, Colorado and New Mexico. A fourth modified
receiver was tuned to 87.9 MHz in the guard frequency just below the
commercial FM band. This receiver functioned as a noise detection system
and was used to prevent recording of local electrical noise such as
lightning (which was probably present to some extent at the time of the
reported fireball observation). The signal used from all four receivers
was the RSSI (received signal strength indicator) voltage, rather than the
actual commercial FM audio signal.
Recording: Outputs of the three receivers were compared and the strongest
one was selected and converted to digital pulses by a DATAQ DI-190 data
acquisition module. Software was set to
record to hard drive (at 40 samples per second) the amplitude of any
signal
above -125 dBm, along with a time and date stamp. The computer clock was
synchronized on an occasional basis with
Parsons Atomic clock software via a phone link to the National Institute
of
Standards and Technology in Boulder, CO. Fireball recording time was
interpolated from time correction offsets before and after the probable
fireball signal was recorded.
Data Analysis: Data analysis was performed by a custom software program.
Anyone interested in a printed recording of the event may contact us off
NET at:
crsvarc@primenet.com
Please send snail mail address and we will forward the printout in a few
days.
Regards
Del Dobberpuhl
Jack Meyer KE4ULK
John Meyer N3EFG
Van Andel Creation Research center
Creation Research Society
Chino Valley, AZ
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