From: "Philip Boucherat" <philip.boucherat@xxxxxxxxxxxx> > Just a general question about scanning algorithms for DVB-C and DVB-S ... > scanning seems quite a difficult problem for DVB-C as for each possible > frequency there are any number of possible symbol rates, and several > possible qam values. I can see from the eutelsat web site that there > seem to be a limited number of symbol rates for DVB-S, but I can't find > any such published information about DVB-C. Actually it is the other way around. Symbol rates for DVB-S vary widely, as the frequency bandwidths of transponders do. In contrast, the selection of frequency bandwidths in cable networks is limited to 6, 7 or 8MHz, and I have yet to hear from any network using DVB-C on any channel raster other than 8MHz. Now with an 8MHz channel, the specified Nyquist roll-off of 0,15 limits the symbol rate to a maximum of 6956 kbaud. Other symbol rates I know of are 6900 kbaud (leaves some frequency margin between channels) and 6875 kbaud (a simple division of the 27500 kbaud of the DVB-S transponders which are fed into the cable network). As to modulation types, I haven't heard of any others than QAM-64, QAM-128 and QAM-256 being used. So in a "blind scan", try the symbol rates 6875/6900/6956 kbaud with QAM-64/128/256. As to the frequencies, your best bet is probably to try the centre frequencies of the standard UHF channels 21 through 69, i.e. 474, 482, 490, 498 ... 858MHz. I think that would at least work on all cable networks in Germany. As for the UK, you will have to see - and report your results back here, please :) Best Regards, -- Robert Schlabbach e-mail: robert_s@xxxxxxx Berlin, Germany _______________________________________________ linux-dvb mailing list linux-dvb@xxxxxxxxxxx http://www.linuxtv.org/cgi-bin/mailman/listinfo/linux-dvb
