[mythtv-users] [OT] coax splitting?

[Gary Balliet]

Omer Shenker wrote:

>Hello,
>
>I have coax running from the wall, and 2 or 3 tuners I want to connect. I'm
>looking for recommendations as to doing this. In the same house I have
>another TV and a cable modem, so I'm worried I need some sort of amplifier
>to have 5 devices connected and still get a good signal in each of them. I'm
>pretty clueless about this stuff.
>
>Both tuners can take either coax or S-video, but the TV's S-video input is
>needed for input from the myth box, so if I want to record 2 w/myth and
>watch 1 wo/myth, the TV needs coax in. Let me try to draw a picture, in
>which data travels down and to the right unless otherwise noted:
>
>CURRENT
>
>+------------+  coax  +------------+
>|box in attic|--------|secondary TV|
>+------------+        +------------+
>   c|       c\
>   o|        o\
>   a|         a\
>   x|          x\
>+-----------+ +------------+ myth +--------+  Sv  +----------+
>|cable modem| |myth tuner 1|------|myth out|------|primary TV|
>+-----------+ +------------+      +--------+      +----------+
>
>WANTED
>
>+------------+  coax  +------------+
>|box in attic|--------|secondary TV|
>+------------+        +------------+
>   c|       c\
>   o|        o\
>   a|         a\
>   x|          x\
>+-----------+ +--------------+
>|cable modem| |mystery device|
>+-----------+ +--------------+
>              ?/  ?|        c\
>             ?/   ?|         o\
>            ?/    ?|          a\
>           ?/     ?|           x\
>+------------+ +------------+ +----------+
>|myth tuner 1| |myth tuner 2| |primary TV|
>+------------+ +------------+ +----------+
>           m\       m|          /
>            y\      y|    -->-->
>             t\     t|   / Sv
>              h\    h|  /
>               +--------+
>               |myth out|
>               +--------+
>
>So what I'm inquiring about is the mystery device (or cable) and the two
>mystery connections, which can either be coax or S-video. The coax running
>from the mystery device to the primary TV would be nice, but I can live
>without it.
>
>FWIW, I have basic (non-digital) cable from Time Warner in the US. All the
>myth stuff is on one box next to the TV.
>
>Thanks in advance,
>  
>
>------------------------------------------------------------------------
>

Hi.

You're going to have a tough go of it there. I work for a cable company 
here in B.C. (yes Harold that company) and the standard that most cable 
companies try to achieve is to get 10db of signal to your house (box in 
attic here i guess) In reality I have seen anywhere from -24 db (noise 
floor) to 18 db.  First thing to remember is that db is a log scale - ie 
2 db is 10x more than 1 db.  Now the first 3 way split will drop you 5.5 
db. per leg, to 4.5 db of usable signal. Next split is the mystery 
device which is also a 3 way splitter (if going passive)  (again a 5.5 
db drop) which will get you down to -1 db. While the ideal is to get 0 
db to the side of the tuner/tv,  I have seen good picture at ~2-3 db (It 
is here that the quality of the tv becomes apparent).  So at this point 
you could still have no problems given 1) a good tuner card   2) 10 db 
at the side  of the house 3) perfect connections to your tuners - ie rg6 
cable and good (read solid one piece crimped on) connectors and premium 
splitters. Any less and you will have problems. Basic cable is usually 
set low in the frequency range so should have less roll-off  and 
therefore better signal than premium. You will notice poor signal by a) 
noise - snow  b) banding  c) poor reception in the higher channels (ie 
above ~45) Best of luck.
Your cable company should be responsive to your needs dependant on the 
number of outlets you are paying for -ie we want to keep you happy but 
if you're ripping us off..... - best bet is to buy an amp and hope it 
doesn't screw up you or your neighbours cable modems. Where i work 
homeowner amps are grounds for immediate disconnection as they can bring 
down a whole node. Remember you now send crap back to us.

Best of luck.

./gary