Hi, On Sunday 11 March 2007 09:40, Trent Piepho wrote: > In dvb-pll, the frequency offset, which is the IF frequency the tuner will > output at, is set to 36.213333 MHz. It looks like this code was written > about two years ago by Patrick as part of the reverse engineered cxusb > driver. > > In saa7134-dvb, there is some totally different code from programming > fmd1216 tuners, and it uses an IF frequency of 36.13 MHz. > > So, why the difference? Usually a (DVB-T) Demod has an capture area of +/- 1MHz relative to the programmend IF and also in most Demods the IF could be moved with certain register settings. I don't know the FMD1216, but in many designs you have a third element which determines the IF frequency, the SAW filter between the tuner and the demod. So depending on which SAW-filter you are using you choose also an certain IF. Epcos for example sells filters with 35.1, 35.825, 36, 36.125, 43.75 MHz and much more. So if you find a SAW-filter on your device, maybe have a look an the datasheet and you will find the right IF. For example, the X6872D which could be found in some DVB-T sticks, has a center frequency of 36.125MHz. (And 6.9MHz bandwidth) If the IF is shifted around 100kHz bit to the center frequency of the SAW-filter and you have a good reception, you wont see much degration in the quality because there are some provision. But if the conditions will go worser, this would make your quality degration a little bit more worse. Kind regards, Thomas Pinz _______________________________________________ linux-dvb mailing list linux-dvb@xxxxxxxxxxx http://www.linuxtv.org/cgi-bin/mailman/listinfo/linux-dvb
