[linux-dvb] fmd1216 integration

Manu Abraham abraham.manu at gmail.com
Mon Mar 12 00:51:03 CET 2007


On 3/11/07, Thomas Pinz <dc2rpt at gmx.de> wrote:
> 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)
>

The TU1216 's have an external SAW filter in comparison to the
internal SAW filter on the FMD1216

linuxtv.org BL my DNS for no reason, thanks to johannes for a timely fix.


manu



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