Searching for Giant Pulses - Andrea (IW5BHY)

NOTE: All the information and images presented here are reproduced with permission by Andrea.

Andrea Dell'Immagine (IW5BHY) has turned over his system to searching for giant pulses from the Crab Pulsar (B0531+21).

Giant pulses are occasional pulses which are more than 10 times the normal average pulse mean flux density.

Background

Andrea has a 3D corner reflector (constructed by Maurizio Gragnani - IU5BEC) a few kilometers outside Barga, Italy.  He has conducted observations of B0329+54 and B0950+08 at this location at 422 MHz.  See Andrea's site here for further details on those observations.

Receiving System

3D Corner reflector (equivalent to a 2.5 metre diameter dish) - fixed pointing (drift-scan mode)
3 panels 2x2mt, wooden frame with metallic mesh - constructed by Maurizio Gragnani (IU5BEC)
Observation bandwidth : 10 MHz with de-dispersion
Preamplifier: LNA 03-70cm from US4ICI (NF = 0.3dB)
Receiver: Airspy SDR
Recording SW: GNU radio channelizer, 2KHz/50 channels format
Back-end SW : PRESTO

Antenna

The 3D corner reflector antenna used by IW5BHY to observe pulsars at 70cm.

 

The Results

 November 2018:

The results of the detection of a giant pulse from the Crab Pulsar as given by IW5BHY.

One of the critical aspects to searching for singular, giant pulses is distinguishing them from a spike of RFI.  This can be done by examining the amount of dispersion of the pulse over the observation bandwidth (a technique also used for confirming Fast Radio Bursts - FRBs).  A terrestrial RFI spike will not be dispersed because it hasn't travelled through the ISM.

Andrea has addressed this in two steps - firstly by showing that the pulse is dispersed (see DM curve in the graphic above) and, secondly, by showing the amount of dispersion matches the known DM value for B0531+21.  This is shown in the graphic below where the observation is split into two sub-bands and the relative delays are measured.

The measured dispersion delay of 6.1 ms/MHz @ 422 MHz corresponds to DM = 55 - which closely matches the published value of 56.8. A nice confirmation.

 January 2019:

Another detection of a giant pulse from the Crab Pulsar as given by IW5BHY.

...with a corresponding dispersion confirmation...

Hunting for giant pulses takes a lot of patience as the two confirmed giant pulses required about 150 hours of observation time spread over about 2½ months !!!

Yet another excellent result from a small antenna !!!