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fredthomsen
Premium
join:2011-03-01
Reviews:
·T-Mobile US
·Comcast

Internet and Satellite sharing same coax

I have searched for this question online and I've seen a variety of answers, most of which are non-technical and simply this is a bad idea and I would never do this without any rational to back it up. I am looking for a concrete technical reason why this should not be done. I want to run the coax from the LNB (Dish Network) and the coax for the Internet (Comcast) over the same coax cable that enters my house.

I do have a DOCSIS 3.0 modem (SB6120) and I know the frequencies range from 5MHz to 1000MHz while the signal coming out of the Dish Network LNB is on the L-Band around 950MHz to 2300MHz, so yes there potential for overlap; however, it seems that my downstream channels are all in the 600MHz range and my upstream channels are in the 20MHz to 40MHz range. Assuming my cable modem keeps the same channels so there is no interference, is it possible to these two services to share a coax entering my home if I use a diplxer to combine them going into the house, and another to split them when the are in the house? Are there other considerations such as power levels that I am not thinking about?

Link to the diplexer I purchased 2 of in case I decide to try this: »www.amazon.com/dp/B0018BS728/ref···410_item


JoelC707
Premium
join:2002-07-09
Lanett, AL
kudos:5

The diplexer you linked skips from 860 to 950 so you won't have to worry about overlap. It could work but if Comcast ever puts any channels above 860, you could run into problems.

Basically you just want a single cable passing through the outside wall as you mention you're going to split the signals after it's inside. Do you not have room to run multiple cables through the wall?

The issue you're going to run into is it's almost certainly not supported by either Dish or Comcast. If you have any issues, they're going to point to the diplexers and say "they're your problem" and you'll have to remove them to get either company to diagnose the problem.


fredthomsen
Premium
join:2011-03-01

Understood. I'll be on my own if I have service issues. Thanks for your help.



beerbum
Premium
join:2000-05-06
Reading, PA
kudos:1
Reviews:
·Comcast
reply to fredthomsen

you really shouldn't run catv and satellite on the same coax.. even if the catv is just cable.. reason being that the satellite system requires power be run through the coax.. that voltage (13-18vdc) can cause interference with the catv signal..

that plus you will likely end up back-feeding that voltage into the catv system itself, and should your cable company discover this your cable will be disconnected.


Midniteoyl

join:2013-11-22
Knox, IN
kudos:1

said by beerbum:

you really shouldn't run catv and satellite on the same coax.. even if the catv is just cable.. reason being that the satellite system requires power be run through the coax.. that voltage (13-18vdc) can cause interference with the catv signal..

that plus you will likely end up back-feeding that voltage into the catv system itself, and should your cable company discover this your cable will be disconnected.

This.. Power over cable.. If you isolate that, the dish switches wont work.

Not to mention prolly fry your modem.

Midniteoyl

join:2013-11-22
Knox, IN
kudos:1

Disregard... I read 'splitter', not diplexer .. Still nursing first cup of joe:)


Midniteoyl

join:2013-11-22
Knox, IN
kudos:1
reply to fredthomsen

Here's a direct answer..

"The hopper uses frequencies in the CATV band (42-900MHz) to communicate between the rooms. You can't mix in Comcast and expect to have this work. DirecTV and Dish Network without Hopper only uses 1.2GHz to 2.1GHz so you could mix in the CATV signals without issue."

from: »Dish Network and Comcast Internet on one Coaxial Cable


harald

join:2010-10-22
Columbus, OH
kudos:1
reply to fredthomsen

How about a lightning hit on the dish?


Aranarth

join:2011-11-04
Stanwood, MI
Reviews:
·Frontier Communi..

said by harald:

How about a lightning hit on the dish?

If it is is properly installed and grounded you MIGHT be ok.

I would say that using a diplexer increases the odds of damage to the catv modem and things connected to it but if you have a direct strike to the house the emp blast is gonna take out all kinds of things anyway.

JoelC707
Premium
join:2002-07-09
Lanett, AL
kudos:5

I had a couple things go wonky (cleared after a power cycle) and many more outright die in one way or another after a nearby strike (just a few houses down the street tops). A direct hit on the dish (or anywhere close by) is going to cause all kinds of problems regardless of the setup.



Johkal
Cool Cat
Premium,MVM
join:2002-11-13
Happy Valley
kudos:9
reply to JoelC707

Comcast does have channels over 860; well into the 1000s.


JoelC707
Premium
join:2002-07-09
Lanett, AL
kudos:5

Partially incorrect. They may have channels over 860, depending on the market, but they most certainly don't have them "well into the 1000s" as the gear running the plant tops out at 1000 MHz AFAIK. Some markets may have older gear that tops out at 750 or 860 (or lower but those would be old and probably abandoned/neglected markets).



Johkal
Cool Cat
Premium,MVM
join:2002-11-13
Happy Valley
kudos:9

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JoelC707
Premium
join:2002-07-09
Lanett, AL
kudos:5

Wrong type of channel. I'm talking frequency channel, not TV channel.


Liberty

join:2005-06-12
Tucson, AZ
Reviews:
·Cox HSI
reply to fredthomsen

I used to install Direct & Dish but has been roughly 6 years or better sine last one.

I frequently would do what you are contemplating using a diplexer.
But for the jobs I was involved with were to preserve their cable internet feed and bring in sat tv.

Can't hurt to try I suppose unless you don't want cable wrapped around house if it doesn't work.


fredthomsen
Premium
join:2011-03-01
Reviews:
·T-Mobile US
·Comcast
reply to fredthomsen

I set this up this weekend and everything is working great. I am not seeing an increase in error counts on the cable modem, and only a slight decrease in SNR. Dish picture still looks great. I added a DC block on each end of the comcast line for added paranoia.

Many asked why I wanted to do this, and the reason is my townhouse is tall and skinny, and the wiring is run outside (not sure whose bright idea that was), and so pulling another cable would have been a hassle.



Kawartha
It's 5 O'Clock somewhere right??
Premium
join:2002-11-11
Peterborough, ON

Glad to hear this worked... had similar questions asked of me here in buildings where one would like SAT and keep CATV inet... thanks for confirming it works


fredthomsen
Premium
join:2011-03-01
Reviews:
·T-Mobile US
·Comcast

No problem. I should add that my cable modem downlink channels were all in the 600 MHz range and if yours are in the top of the DOCSIS 2.0 range (~800MHz) then the potential for interference issues might be greater.

Also DOCSIS 3.0 introduces can have downlink frequencies up to 1GHz, so that would be an issue. I do have a DOCSIS 3.0 modem; however, I would assume the CMTS won't go to that higher range for sometime as those channels would be under utilized as most don't have 3.0 yet (pure speculation on my part).