On 03/31/2016 11:10 PM, Dan wrote:
Hello Radio Heads,
Back in 2001 a burst at 1.4 Ghz from the sky was detected and is known as the
Lorimer burst.
Since then, other groups have detected FRB…Fast Radio Bursts that are very
strong, appear to be extragalactic, and short…milliseconds in duration.
The current theories included young objects that beam radiation. Recent reports
suggests repeating pulses, or repeaters.
Very interesting with work to do!
Some have reported observations using a dipole.
I want to explore a package using a GPS synchronized spectra cadence that would
allow dipole based receivers to stream data from around the globe
in an attempt to create a large radio telescope that could localize these
bursts.
This is where you come in.
I ask you to help me come up with a hardware/software package that uses an SDR
tuned to frequencies with bandwidths of ten Megahertz synchronized by GPS
and channelized to 128 bins at 100 microseconds per frame.
Astronomical bursts travel through Plasma that cause a delay as a function of
frequency known as dispersion.
Local electronic interference like cattle fence, are not so dispersed. Having
wide bandwidth helps sort out the signals that are relevant.
Having 20 or so receivers around the globe really helps eliminate interference and by time of arrival, can localize the position in the sky.
I have played with gnu radio and used SDR to explore radio spectra from LF to
Ghz and all that.
I am not great at gnu radio and know that most in this group have greater
skills than I.
If you would be so kind as to suggest how we may come up with a way to produce
GPS synchronized spectra, we may be able to make it happen.
I envision a band limited preamplifier feeding some SDR with a raspberry
PI…..FPGA? with a GPS to time tagging the data that could be transmitted over
the internet.
From what I gather from the astronomical chatter, is that 400 to 600 Mhz maybe
is the peak of this emission…yet we do not know.
Thus the package would allow one to select a center frequency depending on
local interference.
Thank you for your time and consideration
Dan
The Lorimer burst was 30Jy peak, lasting only a few milliseconds. You
need instruments with *large* effective apertures to "see" such an
event, and I have doubts about the ability to use a mere ca 20
dipoles globally distributed to synthesize such an aperture. Most of the
FRB events that have been logged are a *lot* smaller than the Lorimer
event. Since those stations would likely not be phase-coherent,
then any spectra adding would only improve sensitivity by
sqrt(N)--you don't get to effectively use the sum of the effective
apertures of
the individual stations.
The CHIME observatory, currently entering early operations near
Penticton, BC, has FRBs as a secondary objective, and their antenna
can hardly be described as "a dipole or two".
But, you're the astronomer, so perhaps there's something critical that
I've missed...
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