Re: [dspsr-users] problems with dspsr on 1-pol DFB search mode data

[Marta B. <bu...@oa...>]

Dear all,

note that the problem seems to be with 1-POL data, and not necessarily 
with 1-BIT data (I have not done extensive testing and I don't think I 
have anything 4-pol 1-bit to double-check, but dspsr has the same 
issue also with 1-pol 2-bit data).

As I was saying to Scott, both presto's prepfold and a previous version of 
dspsr do not have any isue with any DFB search mode data. I don't think, 
hence, that that the problem is with changes in the data format.

Cheers,

 	Marta

On Tue, 9 May 2017, John Reynolds wrote:

> Hi all,
>
>> I know that the 1-bit format changed sometime over the last couple
>> years.  The bit ordering in each byte was reversed (i.e. going from LSB
>> to MSB first, or vise versa).  I doubt that that would make this issue,
>
> All Parkes DFB search mode data taken since 2008-9 are 'MS bit first'. Prior 
> to this it was mostly the other way around, I believe.
>
> In 2013 there was a change made to write 1-bit data as CFITSIO type 'B' 
> (byte) rather than type 'X' (bit) . All other bit depths were already being 
> written as type 'B'. This change should have been transparent to the user and 
> was tested by Dick at the time, including with dspsr, and given a clean bill 
> of health. (The change was found to be required to eliminate spurious extra 
> rows being added to the end of the datafile in 1-bit mode).
>
> The last change of any kind made to the DFB code was Sep 2015 and should not 
> have had any affect on the recorded data.
>
> Cheers,
> John Reynolds
>
> On Tue, 9 May 2017, Scott Ransom wrote:
>
>> Hey Marta,
>> 
>> I know that the 1-bit format changed sometime over the last couple
>> years.  The bit ordering in each byte was reversed (i.e. going from LSB
>> to MSB first, or vise versa).  I doubt that that would make this issue,
>> but it is hard to tell.
>> 
>> Have you tried folding the data with PRESTO?
>> 
>> Scott
>> 
>> On 05/05/2017 03:45 AM, Marta Burgay wrote:
>>> Dear all,
>>> 
>>> it looks like the most recent version of dspsr fails to fold search mode
>>> data recorded with the DFB (at both Parkes and the Sardinia Radio
>>> Telescope) with 1 polarization.
>>> 
>>> In attachment you can see an example of what happens folding the same
>>> data file with the same set of ephemeris with an old version of dspsr
>>> (installed through PSRsoft, I believe, in 2015) and with the newest
>>> version.
>>> 
>>> I did a few tests with SRT data (1-pol 1-bit, 1-pol 2-bits) and PKS data
>>> (1-pol 1-bit, 4-pol 8-bits) taken in search mode wih the DFB. The latest
>>> dspsr works fine only on the latter (even though the results are still a
>>> little better with the old dspsr [pdmp SNR 16 vs 15; first channel
>>> saturated with the new dspsr]).
>>> 
>>> I tried both with polyco and predictor and using an ephemeris file or
>>> giving P and DM directly. Nothing changes.
>>> 
>>> I'm not sure whether the problem is directly related to dspsr or if it
>>> depends on psrchive. For SRT data, in fact, I used to install the
>>> development version of psrchive, before installing dspsr. This solved an
>>> issue (a warning about an itoa_code not found) that now, with the
>>> currently available versions of psrchive and dspsr, is back.
>>> 
>>> Is anyone else having the same problem? Any idea of what can be going on?
>>> 
>>> Thanks!
>>>
>>>     Marta
>>> 
>>> ---------------------   (> *  ---------------------
>>> Marta Burgay c/o
>>> INAF - Osservatorio Astronomico di Cagliari
>>> via della Scienza 5
>>> 09047 Selargius (CA)
>>> Italy
>>> tel +39 070 71180 249
>>> fax +39 070 71180 222
>>> ---------------------------------------------------
>>> 
>>>
>>> 
>>> ------------------------------------------------------------------------------
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>>> 
>>> 
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>>> 
>> 
>> -- 
>> Scott M. Ransom            Address:  NRAO
>> Phone:  (434) 296-0320               520 Edgemont Rd.
>> email:  sr...@nr...             Charlottesville, VA 22903 USA
>> GPG Fingerprint: A40A 94F2 3F48 4136 3AC4  9598 92D5 25CB 22A6 7B65
>>
>> 
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>

---------------------   (> *  ---------------------
Marta Burgay c/o
INAF - Osservatorio Astronomico di Cagliari
via della Scienza 5
09047 Selargius (CA)
Italy
tel +39 070 71180 249
fax +39 070 71180 222
---------------------------------------------------