[mythtv-users] PVR250 and static buildup on cable input?

[James L. Paul]

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On Thursday 18 March 2004 18:29, Steven Marcotte wrote:
> Does it kind of look like you are watching TV through a wire pasta
> strainer?  That seems to be the PVR250 wierdness that I experience from
> time to time.  Sometimes I'll go weeks without any problems, other times
> it seems to be a daily occurence.  The problem fixes itself if I
> disconnect the cable input or reboot the computer.

Yah, that's one way to put it, I have sort of a vertical banding with lines, 
and oversaturated dropout also. A quick cable disconnect/reconnect of less 
than a second clears it right up for the next few days or more.

> As for a solution to the problem, I think that is in the hands of the
> ivtv developers.  They have done a wonderful job so far, its only a
> matter of time before the bugs are worked out.

Interesting. I wouldn't have suspected this to be an ivtv driver issue. 
Possibly firmware, but that's the same no matter what driver we use. And I 
disconnect/reconnect the cable so fast that the driver never drops the 
stream. Plus, removing and reloading the driver doesn't affect the problem, 
neither does rebooting the machine. The image problem is persistent until I 
disconnect the cable input briefly.

It is very similar to a problem I've encountered in cable TV signal 
distribution with a broken coaxial cable. If the cable has a very tiny break 
or gap in the center conductor, it can still transfer the RF energy even 
though it's not solidly conducting. Over time static charge can accumulate 
and result in signal quality changes similar to what I am seeing. I'm ruling 
this out though because another main effect of this kind of problem is that 
it gets worse with higher frequencies since the RF energy loss is 
proportionate to frequency. With the broken cable the higher channels are 
noticeably worse than the lower channels, and my problem is independent of 
channel number. Also, if my main input cable was bad, it would more likely 
affect all my tuners, not just the two PVR250's.

I'm actually considering a temporary workaround of putting A/B switches inline 
to my cards, with the B side disconnected. At least it would make it easier 
to clear up the signal by not having to fumble with the F-connectors. :) I 
hate considering such a kludge though.

> Cheers,
> Quattro
>
> On Wed, 2004-03-17 at 22:06, James L. Paul wrote:
> > Here's something I've been dealing with for a few months, and am
> > wondering if anybody else has had the same problem or a solution...
> >
> > Every few days my signal quality deteriorates, it's hard to describe, but
> > basically I get symptoms of poor cable signal to one or both of my PVR250
> > cards.
> >
> > I can immediately clean up the signal by simply disconnecting and
> > reconnecting the coaxial cable from the affected tuner(s). I've tested
> > and replaced cables and connectors multiple times, and have determined
> > that this reliably fixes the problem, although temporarily. Sometimes it
> > stays good for a week or two, and sometimes only a few days. I have 4
> > devices fed by my cable, all from the same distribution amp, only the 2
> > PVR250 boxes are affected. Perhaps I have a grounding problem or
> > something else odd?
> >
> > Anybody have ideas for the cause or a permanent fix?
>
> !DSPAM:405a84cb76635219480934!
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