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

[Willem v. S. <van...@gm...>]

Hi Marta,

I looked into this problem today and found that the problem appears to be
related to new code added to dspsr in 2016 that applies the scales and
offsets recorded in the PSRFITS file.  Resetting the scale to unity and
offset to zero recovers a plot that is more like old_dspsr.ps

The scales and offsets applied when producing the PSRFITS file likely
flattened the bandpass, which is desireable in many cases, but applying the
scales and offsets when unpacking undoes this goodness.  I plan to add an
option to dspsr so that application of scales and offsets is an option; the
default value for this option will return dspsr to its original behaviour
(not applying scales and offsets when unpacking).

Cheers,
Willem


On Mon, 8 May 2017 at 11:06, Marta Burgay <bu...@oa...>
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
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> Italy
> tel +39 070 71180 249
> fax +39 070 71180 222
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