Presto data file format

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Jack Lobingier

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Apr 29, 2021, 5:03:35 PM4/29/21
to Society of Amateur Radio Astronomers
I have a question for those of you that have been doing pulsar work using data from your own antennas.  For those of you who use Presto, how do you format the data you collect so that it is readable by Presto?  Also, if you are willing to pass on examples of that format, that would be very helpful.  Thank you.

Jack

fasleitung3

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Apr 30, 2021, 3:43:18 AM4/30/21
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HI Jack,
Presto can read a number of different formats. Many people including myself use the filterbank format. This is what I would recommend as a number of people here will probably be able to help with this.
Generically speaking a filterbank file has a header, followed by binary data where such binary data represents a spectrum for each sample period. The binary data can come in either 8-bit integers or 32-bit floats as defined in the header. How do you get to such a file? This is where I would ask other people to step in with practical implementations. I personally have been standing on the shoulder of giants as I am using software from the professionals to get the data from our pulsar spectrometer. I am also using SDRs for pulsar observations and in this case I am using a Gnu radio based implementation from others to create the filterbank file.
There are two different approaches which are used in the amateur community: One approach is to record the raw IQ data and then do the FFT and writing of the filterbank file in a subsequent offline step. The disadvantage here is the large amount of data which is generated. The other approach is to do the FFT on the fly and then write the filterbank file directly . Here one needs to take care that the processing power is good enough to do the FFT without loosing samples. I will leave it at that as others are more into this subject.
Unfortunately there is no document that I am aware of which describes the filterbank format. If you are interested in the details and want to do something by yourself you may want to look into pysigproc (https://github.com/devanshkv/pysigproc) which has routines to work with filterbank files and headers.
Best regards,
Wolfgang

Am Donnerstag, den 29.04.2021, 14:03 -0700 schrieb Jack Lobingier:
I have a question for those of you that have been doing pulsar work using data from your own antennas.  For those of you who use Presto, how do you format the data you collect so that it is readable by Presto?  Also, if you are willing to pass on examples of that format, that would be very helpful.  Thank you.

Jack

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Jack Lobingier

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Apr 30, 2021, 6:11:34 AM4/30/21
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Wolfgang, thanks for your help on this.  There is a GRC application from Marcus Leech at CCERA that collects data and writes to a filterbank file, and as that would be ok to use with Presto, I will look into that.  There was an earlier discussion on using a Pi4 with a GPS board to produce better time sync info, so I will look into that as well.  Thanks again.

Jack

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