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

Joseph A. Caputo jcaputo1 at comcast.net
Fri Mar 19 09:31:39 EST 2004

On Friday 19 March 2004 01:55, James L. Paul wrote:
> 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.

I had similar symptoms last night... my picture quality on both my 
M-179's had deteriorated; one with oversaturated colors, the other not 
quite as bad, but noticeable.  A reboot didn't help, but unloading/
reloading the ivtv driver not once, but a couple of times, seemed to 
finally fix the issue.


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