Measurements of spatial and frequency coherence of an equatorial hf path during spread-F
In August 1990, the authors set up an hf path on the equatorial path between Maloelap Atoll and Bikini Atoll. This path, which had a range of 702 km, reflected in the ionosphere approximately 100 km north of the Altair radar location on Kwajalein. Transmitters at Maloelap broadcasted four cw tones within bandwidth of either 4 kHz, 9 kHz, or 70 kHz to be used to determine frequency coherence and also a phase-coded pseudo random sequence with a bandwidth of 60 kHz (channel probe) to be used to determine time delay spread. A spatial array of antennas was deployed at Bikini to measure spatial and frequency coherence using the cw broadcasts. The system was run in the post-sunset time period over two weeks during which almost every night showed significant degradation due to spread F resulting in rapid fading, decreased spatial and frequency coherence, and increased time delay spread. Doppler spreads of greater than 20 Hz were not uncommon, and the spatial correlation distances and frequency coherence bandwidths became so small (50 meters and 1 kHz respectively) that the experiment had to be readjusted. Measurements taken by the Altair incoherent scatter radar and the CUPRI 50 MHz coherent scatter radar indicate that although the bistatic hf channel is affected by the large scale plume structures, most of the [open quotes]damage[close quotes] is done by the bottomside spread F.
- Research Organization:
- Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
- Sponsoring Organization:
- USDOD; Department of Defense, Washington, DC (United States)
- DOE Contract Number:
- W-7405-ENG-36
- OSTI ID:
- 7368684
- Report Number(s):
- LA-UR-93-2140; CONF-9306190-1; ON: DE93016615
- Resource Relation:
- Conference: TENERP conference, Monterey, CA (United States), 21-24 Jun 1993
- Country of Publication:
- United States
- Language:
- English
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Equatorial spread {ital F} effects on an HF path: Doppler spread, spatial coherence, and frequency coherence
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Related Subjects
GENERAL PHYSICS
IONOSPHERE
SIGNAL DISTORTION
RADIOWAVE RADIATION
WAVE PROPAGATION
DOPPLER BROADENING
MHZ RANGE 01-100
SPREAD F
EARTH ATMOSPHERE
ELECTROMAGNETIC RADIATION
F REGION
FREQUENCY RANGE
LINE BROADENING
MHZ RANGE
PLANETARY IONOSPHERES
RADIATIONS
661300* - Other Aspects of Physical Science- (1992-)