[linux-dvb] Re: DVB-T and zigzag scans question

[Ragnar Sundblad <ragge@nada.kth.se>]

--On den 24 juni 2003 12:49 +1000 John Dalgliesh 
<johnd@syd.microforte.com.au> wrote:

> I have no idea how I'd go about modifying the TDA10045H driver to use a
> different step size. As far as I can see, 167kHz is the resolution of the
> current calculation (1MHz/6) ... so I'd have to actually understand how
> those registers and the values written into them work... which I don't 8)
You would have to look in the tuner PLL circuit spec and see how
to program it with another step size (if at all possible).
The tuner PLL is on of the chips in the metal box. Its purpose
is to make a signal that when mixed with the wanted input signal
will make an IF signal of some constant and typically pretty
low frequency, like 30 MHz or so, that is fed to the demodulator.
In other words, it is programmed to generate a signal that is
X Hz above or below the wanted signal, where X Hz is the center
frequency that the demodulator wants its input signal to have.

You may be able to program it for another step size, which mean
that you would also have to change 1/6MHz constant in the
calculation accordingly.

Many of those PLLs seems to be very similar (in my very limited
experience) and many of them can be programmed for two different
step sizes. Note that the tuner module may use a different
crystal frequency than the example in the PLL data sheet -
you should be able to find out by the current tuning calculation.

I am not sure that you should have to, though, since I think
the demodulator should be able to correct such a small offset.
But I don't know, I know nothing about this demodulator.

Good luck!

/ragge




--
Info:
To unsubscribe send a mail to ecartis@linuxtv.org with "unsubscribe linux-dvb" as subject.