[mythtv-users] Signal strength issues changing from NTSC to QAM256

[Tony Sarathchandra]

So at the start of this month, the much discussed analog to digital cutover
of Comcast channels >32 occurred in my area (Bay Area). Prior to this change
I had been happily receiving channels 2-89 or so via the NTSC input of my
HVR-1600 MythTV BE/FE setup.  I had been using the ATSC input of the
HVR-1600 for OTA DTV as well which was working well.

So I temporarily disconnected the OTA ATSC input, hooked up the Comcast
cable to this input, changed config to QAM256 in mythtv-setup and did a
scan, nothing!  After fiddling a bit the details of which I will spare here,
I found that I was able to pick up most of the QAM channels, albeit some
quite poorly, if I bypassed the 3-way splitter which I was using to split
the Comcast signal between the HVR-1600 and my older AVerMedia TVPhone98
(bttv compatible) card being used as a second tuner near my MythTV BE
server. Here's a primitive diagram of how the coax cabling is laid out at my
place.

 
|----3.5dB-------->HVR-1600 NTSC input (MythTV Backend)
  Comcast cable in--->[SV-2G 2-way splitter]---3.5dB------>[SV-3G 3-way
splitter]|----7.0dB-------->HVR-1600 ATSC/QAM input (MythTV Backend)
				|
|----7.0dB-------->AverMedia NTSC input (MythTV Backend)
				|------------3.5dB------->TV           

I have an initial 2-way splitter as you can see going to a TV in another
room. I'm guessing that the signal level after this initial 3.5dB loss and
the subsequent 7.0dB loss is not sufficient enough to the QAM tuner to
detect a strong enough signal.  Any thoughts on how I can alleviate this
situation as I do need the splitters in place to use all the tuners in the
house? 

Should I invest in a cable amplifier at the initial 2-way splitter point?
Would this improve the QAM signal strength sufficiently? I've also been
looking adding a second ATSC/QAM tuner to my setup as I do want to receive
OTA DTV as well, would something like a HD Homerun be more able to operate
with lower signal levels that the HVR-1600? Any feedback much appreciated.

Thanks

Tony


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