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

Douglas Peale Douglas_Peale at comcast.net
Wed Jul 21 19:34:07 UTC 2010

Hash: SHA1

On 07/21/2010 05:55 AM, Brian Wood wrote:
> On Wednesday, July 21, 2010 04:17:51 am Craig Huff wrote:
>> And another problem...
>> In the setup directions for the DC50Xu, after directing that the DTA
>> be set to channel 3 for set-up, there is a note: "Note: Some parts of
>> the country use channel 4.  If you do not have a picture after
>> completing the activation, you may need to switch both your TV and the
>> DTA to channel 4."
>> Does anyone know it that means my scheme described above of combining
>> one DTA outputting on channel 3 with one on channel 4 is toast?
> STBs (and their predecessors, "converters") usually output on wither channel 2 or 3, or channel 3 or 4. This is so that 
> you can use a channel that is not used over-the-air in your area, to prevent interference. In the says of single-braid 
> RG-59, before quad shielded cables, this was necessary. Generally adjacent channels are not used in any market, so at 
> least one of the available output channels would be usable.
> Now that most OTA stations have moved to UHF (there are exceptions), it's more likely that you will have both 2 and 3, or 
> 3 and 4, clear of any OTA signals, so you might think it would be OK to use both.
> The problem is the output of STBs is extremely "dirty", the output on channel 3, for example, is very likely to throw crap 
> that's within the channel 4 bandwidth. Also, the aural carrier from an STB's modulator is down by 10 db., which is normal 
> for OTA broadcasts, and will throw "beats" into the upper adjacent channel. Cable companies run aural carriers at 15-17 
> db. down, in order to be able to use adjacent channels without problems.
> So there is a very good chance that combining the outputs of two STBs will result in crap from one interfering with the 
> other, unless good filters are used in the combining network, which is expensive (and is the reason the STB outputs are not 
> well-filtered, too expensive).
> It might work, but I'd expect problems. You'd have to try it out I guess.
> A couple of high-quality bandpass filters would probably help, but would cost more than your entire Myth setup.

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.

Let us know the results.
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