[ivtv-users] hvr-1600, frame CRC mismatch - incomplete frame

[Andy Walls]

On Thu, 2010-02-18 at 10:33 -0500, Kyle Lil wrote:
> 
> 

> OK, so I built an attenuator with a potentiometer in position Z2 for
> the circuit diagram you sent me. I'm sure there are probably a whole
> slew of problems this could introduce (especially since I did not put
> a pot in position Z1 also), but I wanted to be able to easily look at
> the various attenuation levels (and I don't have a soldering iron at
> home, just at work). What I found was that the glitches are still
> apparent even when I turn the potentiometer to a level that make my
> cable box OOB AGC go to >30% (which it now rates as "fair" instead of
> "good"). The cable box and HVR-1600 are at the output of the same
> splitter, which is after (downstream of) the adjustable attenuator I
> built. The way I constructed the circuit, I could not provide enough
> attenuation to cause the tuner to lose station lock, but with the
> maximum attenuation (~-14dB from attenuator + -6dB from the two
> splitters between the HVR-1600 and the wall) I could achieve, the
> glitch rate was the same (or maybe slightly higher).

Hmmm.  Crud, io suspect there must be something else going on.

My next guess is that the HVR-1600's AGC is responding too quickly (or
too slowly?) to variations in the incoming signal.

I'll have to think about it though.

Since I have a somewhat similar condition on two ATSC stations, I'll
work up a debug patch for the s5h1409 driver that reports some more
stats from the CX24227.  I have never used the additional statistics
registers before and I don't have much faith in the documentation I
have, so I'm not sure if they work or will be useful.   We'll see.  I
won't be able to do anything until Saturday night at the earliest.



>  
> 
> I will try to build an attenuator today that is able to reduce the
> signal all the way down to an un-lockable level. Is it possible that
> the HVR-1600 is so sensitive that a signal level my cable box rates as
> only fair is still too large for it?

I would doubt it, but it still could be the case.

I think if we can get more stats from the CX24227 chip, we may get more
insight as to what might be wrong.

Regards,
Andy