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

[Andrew de Quincey <adq_dvb@lidskialf.net>]

On Saturday 21 June 2003 16:10, Robert Schlabbach wrote:
> From: "Andrew de Quincey" <adq_dvb@lidskialf.net>
>
> > With DVB-T, the zigzag scanning code chooses a step size as follows:
> >
> > stepsize = fe->info->frequency_stepsize * 2;
> >
> > frequency_stepsize for OFDM frontends seems to be set to 166667 usually,
> > which means it zigzags using a stepsize of 333334.
> >
> > Thing is, in my experience, frequency bending doesn't work for DVB-T
> > either.  Using a stepsize of 166667 for trying to lock on to a slightly
> > displaced signal is way too large, let alone 333334.
>
> Hmm, it makes perfect sense to me. The TDA10045H supposedly can detect a
> signal within +/-167kHz, so you'd check this range by querying its
> registers, then use the zigzag scan to check the adjacent ranges...

I was basing this on my experiences with other tuners... they are unable to 
detect the signal unless the tuner is at the correct frequency anyway.. 
frequency bending just serves to break tuning, and I was wondering if a 
zigzag scan had the same behaviour. e.g. this causes such great problems with 
machines with > 3 DVB-T cards that I always comment out the 
fe_bend_frequency() line in dvb_frontend.c



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