#91 Some problems about digifil

[Wucheng Huang]

When I try to use this one command,
digifil -cont -q -F 128:D -E J0024-7204C.par -D 24.599 -o J0024-7204C_1.fil G0057_1227009976_109.hdr.Then this one channel 's vidf data will turn to fil data.I have 24channels and it means I will have 24 fil data.Then if I use 'splice' to combind all the frequency together,it shows this one error:start time in input files are not identical!
Thanks for your help!

[Andrew Jameson]

Since you are performing coherent dedispersion in each of the single channels, DSPSR must discard some of the data at the very start of the file since it is corrupted by the application of the dedispersion kernel. The amount of data that is discarded depends on RF frequency in each channel, with the lower channels requiring more samples to be discarded.

You could avoid this problem by:

1. Not performing coherent dedispersion when using digifil.
2. Use digifits (to produce a PSRFITS search mode file instead of sigproc) since it has a "-s" option which allows you to set an offset in the output file to account for this delay.
3. Use dspsr to produce folded archives and combine those with "psradd -R"

The other option would be to add the start offset feature to digifil, but this would require some developer time to complete.