[mythtv-users] How to best deal with Comcast's "Improved" Lineup?

Brian Wood beww at beww.org
Wed Jul 21 21:17:33 UTC 2010

On Wednesday, July 21, 2010 03:02:34 pm Douglas Peale wrote:
> On 07/21/2010 01:22 PM, Brian Wood wrote:
> > On Wednesday, July 21, 2010 01:34:07 pm Douglas Peale wrote:
> >> You won't know until you try, but trying is really cheap. just get a 2
> >> way splitter and use that to combine the signals, and give it a try. If
> >> you don't already have a splitter, it will cost you about $5.
> > 
> > It would be better to use directional couplers to do the combining, and
> > not hybrid splitter/combiners, as you would get much better isolation
> > between the two devices being combined. The isolation spec on hybrid
> > combiners is based on the assumption that each port is seeing precisely
> > 75 ohms, while with DCs the isolation isn't dependent on precise
> > termination, and the isolation is better in any case.
> > 
> > The problem is that you would lose more signal by using DCs. I don't know
> > what level the devices put out, it would have to be at least +10 dbmv.
> > or more, assuming 8 db. loss DCs.
> > 
> > Might not work well, due to insufficient output levels, I just wanted to
> > point out that DCs make a much better combining network than hybrid
> > splitter/combiners do.
> > 
> > A couple of DC would run about $10 or $12, more than a splitter, but
> > technically a better solution.
> 1) a directional coupler is more expensive
> 2) a directional coupler is harder to find
> 3) a directional coupler may not be necessary
> 4) a directional coupler will not help if the source is crappy and mucks up
> adjacent channels. 5) he still won't know until he tries.
> Do the simplest cheapest test first. If that does not work, then start
> worrying about alternatives.

All true. If it were me I would simply go to the "DC" drawer in my junk closet, but I realize not everyone has one of 

IMHO the cable company should provide the DCs, any installer generally has a bunch of them on their truck. If they are 
needed to make the cable company's gear work properly, they should provide them, though I realize there may be a difference 
of opinion about what "work properly" actually means.

Certainly can't hurt to try hybrid splitters, but if they "almost" work, the additional isolation of DCs might push the 
system over the edge into "working".

My main purpose was to make sure the OP knew that DCs are a better solution for combining sources, even if splitters turn 
out to be "good enough".

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