[vdr] feeds

Hi, I'm trying to tune fta(free to air) feeds with VDR. Feeds are temporaly channels for an event that usually have low freqüencies. To tune them I try to add or edit channels in my list. But I only know this for example:

30W (hispasat) frequency: 11538 polarization: H sr 6100

Some of this feeds are in 422 format. I have a nexus-s dvb-s FF card. My question is if there is a method to force the pid update of a channel because I don't know this data. I know the update names and pid option of the dvb card configuration but I don't know exactly how works. It seems that I have to wait VDR to update all channels.

Thanks.