This paper presents a search for radio transients at a frequency of 73.8 MHz (4 m wavelength) using the all-sky imaging capabilities of the Long Wavelength Demonstrator Array (LWDA). The LWDA was a 16-dipole phased array telescope, located on the site of the Very Large Array in New Mexico. The field of view of the individual dipoles was essentially the entire sky, and the number of dipoles was sufficiently small that a simple software correlator could be used to make all-sky images. From 2006 October to 2007 February, we conducted an all-sky transient search program, acquiring a total of 106 hr of data; the time sampling varied, being 5 minutes at the start of the program and improving to 2 minutes by the end of the program. We were able to detect solar flares, and in a special-purpose mode, radio reflections from ionized meteor trails during the 2006 Leonid meteor shower. We detected no transients originating outside of the solar system above a flux density limit of 500 Jy, equivalent to a limit of no more than about 10 −2 events yr −1 deg −2 , having a pulse energy density 1.5 × 10 −20 J m −2 Hz −1 at 73.8 MHz for pulse widths of about 300 s. This event rate is comparable to that determined from previous all-sky transient searches, but at a lower frequency than most previous all-sky searches. We believe that the LWDA illustrates how an all-sky imaging mode could be a useful operational model for low-frequency instruments such as the Low Frequency Array, the Long Wavelength Array station, the low-frequency component of the Square Kilometre Array, and potentially the Lunar Radio Array.

On 10 January 2009, an unusual ionospheric scintillation event was observed by a Global Positioning System (GPS) receiver station in Fairbanks, Alaska. The receiver station is part of the National Geospatial‐Intelligence Agency's (NGA) Monitoring Station Network (MSN). Each MSN station runs two identical geodetic‐grade, dual‐frequency, full‐code tracking GPS receivers that share a common antenna. At the Fairbanks station, a third separate receiver with a separate antenna is located nearby. During the 10 January event, ionospheric conditions caused two of the receivers to loose lock on a single satellite. The third receiver tracked through the scintillation. The region of scintillation was collocated with an auroral arc and a slant total electron content (TEC) increase of 5.71 TECu (TECu = 1016/m2). The response of the full‐code tracking receivers to the scintillation is intriguing. One of these receivers lost lock, but the other receiver did not. This fact argues that a receiver's internal state dictates its reaction to scintillation. Additionally, the scintillation only affected the L2 signal. While this causes the L1 signal to be lost on the semicodelessly receiver, the full‐code tracking receiver only lost the L1 signal when the receiver attempted to reacquire the satellite link.

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This paper describes the application of the Fast Number-theoretic Transform (FNT) to the processing of GNSS signals. This FNT is an alternative to Fast Fourier Transform (FFT) techniques and efficiently provides bit-for-bit identical results to a traditional time-domain correlator without the need for word-length growth or the quantization of irrational complex roots of unity. We document a prototype single channel GPS C/A code receiver with a continuously operating correlator that computes hundreds of lags. The design is implemented with an inexpensive Field Programmable Gate Array (FPGA) programmed to implement the FNT. As an initial application, we present a multipath investigation using this receiver in which we were able to localize and then identify the source of the multipath signal.

Existing literature documents a number of techniques for combining a set of independent datapath designs into a single datapath that is run-time configurable to the functionality of any datapath in the set. This paper explores how delay, energy and area overhead attributable to reconfigurability scales with the number of configurable functionalities, independent of the design of specific datapaths. Distinct design space regions are identified based upon common scaling properties, with implications on the design and feasible efficiency bounds of reconfigurable devices.