[linux-dvb] Re: Problems with a DVB-T

[Holger Waechtler <holger@convergence.de>]

Ragnar Sundblad wrote:
> 
> I am struggling on with my DVB-T card.
> 
> I still have very bad reception. I have tried several tricks
> with the antenna signal, for example I made a simple high
> pass filter, and have gotten it to improve somewhat, but it is
> still far from good or acceptable.
> 
> Any hints, tips or tricks are mostly welcome!
> 
> I now need some help from you tuner/frontent people out there.
> 
> The tuner is an ALPS TDLB7 without internal D/A and has a
> pinout which is a mix of this: 
> <http://www3.alps.co.jp/WebObjects/catalog.woa/HTML/BroadcastingComponent/T
> errestrialTuner/TDL/TDL_E.HTML>
> and this: <http://www.alps.co.kr/pdf/eng/01/eb0601c.pdf>
> (it has the pins 16..19 as the Korean TDLB7 but the rest as
> the Japanese one, and it is missing pins 20..32).
> 
> Question 1:
> The module is supposed to get 9V and 32V, it gets 8.75V and
> 28.85V on those pins. How critical are those voltages?

These tolerances should be specified in the datasheet, not? Usually they 
are only about a few volts for the PLL charge pump voltage and a few 
10th volts for all lower voltages.


> Question 2:
> The module is made for 470..862MHz. Could my problem be
> that there are lower frequency signals in my RF feed that
> interferes in the tuner? In other words: that the
> first filter doesn't remove lower frequency signals
> good enough (I think)?
> 
> Question 3:
> Does anyone have any other good ideas on what to look for?

maybe you can improve things by playing with PLL and AGC register settings.


> Question 4:
> What is "AS" signal (pin 9)? I am just curious.

adress select. For some tuner modules you can change PLL and/or 
Demodulator i2c adress by toggling one adress bit on this line.

Holger



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