Re: [PATCH] FM1216ME_MK3 some changes

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On Sat, 2009-05-02 at 01:55 +0200, hermann pitton wrote:
> Guys,
> 
> [snip]
> 
> > > 
> > > Do the circuit board traces in the FM1216ME_MK3 support the TDA9887
> > > controlling the gain of the first stage?  (I've never opened an
> > > equivalent NTSC tuner assembly to take a look.)
> > 
> > "equivalent" NTSC tuners _do not_ exist at all.
> > 
> > I don't forget all the time we spend to find out that some of them are
> > Intercarrier only!
> > 
> > Also, the tda988x stuff is underneath the tuner PCB.
> > 
> > I cut one off for those interested in line tracing ...
> 
> still on the to do list ;)

Thanks.  I hope it doesn't cost you too many wasted Euros...

> > Without port2=0 you don't get any SECAM-L into the sound trap.
> > 
> > It needs amplification from minus 40 dB AM for the first sound carrier,
> > and then of course you prefer the second with NICAM.
> > 
> > > If not, then, if I understand things correctly, you need to set the
> > > first stage and second stage TOP settings so that they refer to about
> > > the same signal level before the IF SAW filter.  
> > > 
> > > 
> > > I would think AGC TOP settings, for both stages of the tuner, are
> > > tuner-dependent and relatively constant once you figure out what they
> > > should be.
> > > 
> > > Do you have a different understanding or insight?
> > > 
> > > Regards,
> > > Andy
> 
> Hartmut once offered to make contacts with colleagues at Philips Hamburg
> for such tuners and related tda9887 stuff.
> 
> Unfortunately he is not active on the lists currently.
> 
> If I see, how easily someone can get a patch to Andrew and disables all
> other SECAM stuff, again from Russia, I'm not convinced on anything from
> there.
> 
> I seriously doubt that those tuners are meant for fumbling on TOP RF/IF
> settings from user space.

The proper TOP settings should be a function of the input signal TV
standard (positive modulation vs. negative modulation vs. FM radio) and
the components in the tuner assembly (the IF filter for sure).  Setting
TOP settings from user space only makes sense for laboratory
experimentation.


Linux is kind of funny in the way it breaks up the integrated assembly
of an analog tuner to be handled by separate drivers: preselector and
mixer/osc chip by tuner-simple; IF filter and IF demod by another module
like tda9887.  Really the two chips should be set with coordinated
settings, taking into account the TV standard the tuner is being set to
demodulate and the properties of the IF filter and external components
to the IF demodulator.


The linux analog tuner drivers mostly appear to make some safe, default
settings, and don't attempt to get the best performance.  I'm assuming
that is due to lack of data on the tuners and the tuners working well
enough.

I'm glad to see Dmitri working at trying to improve analog performance.

I wish I had the proper equpment to experiment wih NTSC tiners.  If I
had a lab with a decent signal generator, oscilliscope, etc. I'd
probably have lots of fun playing around with these tuners. :)

Regards,
Andy


> Cheers,
> Hermann


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