[mythtv-users] Pixelation/Bad Recordings HDHR Prime -- I am at my wits end

[Gary Buhrmaster]

On Tue, Aug 27, 2013 at 8:30 PM, Stephen P. Villano <
stephen.p.villano at gmail.com> wrote:

>  That sounds like one of the filters used back before Comcast switched to
> digital. We used to have stacks of them in series, each filter for each
> premium channel.
> Comcast installers frequently have a bad habit of leaving that junk behind.
>

Those would be notch filters (they attenuated the premium channel
frequencies, or the TV frequencies when you only had a cable modem,
or....)

In any case,  in today's cable plant, almost all of those filters are
badness,
as Comcast moves channels around various frequencies, eventually they
may move something to where the notch filter is/was, and the signal is
too low to be useful.

Since you mentioned the problem comes and goes, you may have a
RF leakage issue (and it may be in your wiring, or the outside plant).
This can be a common problem where the MSO decides to use the
frequencies in the FM band.  FM signal comes in, and generates
"random" noise that results in bad pixelation.  And while if the MSO
has extra bandwidth, there is a tendency to avoid the FM band for
precisely this problem, Comcast is known to use that band (I had
a hardline broken at a pedestal near me, which resulted in bad
pixelation for the channels that shared the FM band; the QAM
constallation was the classic one for that case; it could have been
used in the tutorial).

Before spending any more time try to rework your cabling, call Comcast
and request the removal of the notch filters, and have them check the
signal levels at your demark, and the noise levels across the spectrum
to insure there is no leakage.  In most cases, for the appointment, the
best thing to do is to say some channels do not work, and the picture
either freezes, or breaks up.  When the tech gets there, the first thing
they will likely do is remove the notch filters and check the levels
(because that is the first thing you check).

Gary
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