CATV Splitter

[kaneohe]

I think I know that if a splitter connects to 2 separate TVs, that roughly
50- % of the incoming signal goes to each side. What happens if one side is disconnected at the splitter(open) but the other side remains connected vis the splitter. Does the remaining side get 100-% of the incoming signal or 50-%?

 

[FIREmenow]

I'm pretty sure it would still be 3.5dB (50%) loss due to the hardware and connections inside. You should probably also put a 50Ω or 75Ω (depending on your system) termination on the unused port to keep RF reflections down.

 

[Big_Hitter]

I'm pretty sure it would still be 3.5dB (50%) loss due to the hardware and connections inside. You should probably also put a 50Ω or 75Ω (depending on your system) termination on the unused port to keep RF reflections down.

Yes

 

[kaneohe]

Thanks, FIREmenow and Big_Hitter. I'm hoping you're right. I've had intermittent issues w/ the CATV. This past wk was particularly bad with picture breakup, no sound, or just a screen w/ blue boxes w/ error message and promises that the channel would be back soon. Usually the reception would be ok sometime after calling Comcast.......either they would have me reboot the CATV box, or they would reset the box remotely or something.......but the next day, usually in afternoon, the problem would recur. On Friday,they must have had a bigger area problem as no help was available and only a message that I could have them call me when things were fixed.

Saturday AM, things were fine again and then in PM, the usual problems started. CSR reset box and things got good. In the process she had asked about whether I had a splitter but didn't follow up. That triggered the thought
in my mind that maybe I should remove the splitter and associated coax extension cable and hopefully get a stronger signal. I removed those pieces on Sat PM after things had gotten better w/ the original setup so I didn't really see
a difference at the time.

Hopefully based on your replies though, the signal strength increased so perhaps I may be less susceptible to the problems I was having.

 

[Just_Steve]

Thanks, FIREmenow and Big_Hitter. I'm hoping you're right. I've had intermittent issues w/ the CATV. This past wk was particularly bad with picture breakup, no sound, or just a screen w/ blue boxes w/ error message and promises that the channel would be back soon.

I had similar issues and called my cable company they came out and checked the incoming signal strength which was good before the splinter but very low at the 5 TV's. Their solution was to us an electrical powered amplifier/splitter.
No issues since.

 

[Big_Hitter]

yes get an amplifier - i have mine amplified after it's split for the downstairs internet/tivo feed to the other 3 TVs - no issues at all

I should upload a photo of my cable box

 

[Big_Hitter]

every time you use a splitter you are shortknocking the signal

last year they had to replace the cable going into the house because it was "ancient" - after that I stopped having problems with the modem - i hung out with the cable guy and learned a few things (you retired guys must really get on their nerves lol) - DW has no idea where the cables are or where they go to or what they do

 

[John Galt III]

Similar problem here with my cable tv. Certain channels are often choppy and pixilated, and a lot of the channels have a message saying "sorry, no signal, contact cable company". Called the cable co and they asked if I had a splitter. I looked, and yes, I do have a 2 way splitter in the basement. One port is disconnected. Cable csr implied the splitter was defective/old/ needed to be replaced possibly. I tried to remove the splitter completely and just have one cable line going to TV, no splitter, but the splitter is made out of some brass-colored tube that doesn't want to come off (maybe a special tool is needed?). So the splitter is still on. CSR didn't mention amplifier. Where would I put the amplifier? Could I attach it near the TV at the cable in port?

 

[Big_Hitter]

I think you need to get rid of that splitter and splice it with a barrel. You should be able to get some connectors and ghetto crimp them with pliers.

How To Crimp a Connector onto a Cable at The Home Depot

see if that works, if it doesn't try an amplifier as close to the box as you can

 

[misanman]

A couple of years ago we were having some problems with our Comcast service and they came in and cleaned up the in-house stuff by removing splitters, disconnecting unused runs, and installing a new amplifier. They measured the signal at the end of each drop to make sure it was up to spec. This, together with a new cable run from the street solved the problems we'd been having.

 

[kaneohe]

Similar problem here with my cable tv. Certain channels are often choppy and pixilated, and a lot of the channels have a message saying "sorry, no signal, contact cable company". ...............

I think my message said something "temporarily unavailable; be back soon"
Curious which channels have the problem. Mine was channels 1-20 and
> 90. The ones in between were fine. Don't understand why ....the lower channels were "local" stations.

 

[Root]

Most 2-way splitters reduce the signal levels by 3.5dBmv. Amplifiers should not be used unless the power measured on an RF meter is less than 3.5dBmv before the splitter.

Ideally 0dBmv (digital) is enough signal for the cable box. It is possible to "overdrive" the RF tuner in some boxes by giving it more signal than necessary.

Also, please make sure that all splitters are capable of passing frequencies over 750Mhz or else you may be accidentally causing more problems by blocking RF carriers.

 

[Koolau]

Two different locations I used the splitter supplied by the cable co. Both gave problems but the cable co. kept putting me off. Both times, I eventually threatened to drop their service and they brought out an amplifier which solved the problem. With all the cable boxes, amplifiers, internet boxes, etc. I must have a huge "phantom" load using up a lot of monthly KWs. YMMV

 

[Just_Steve]

This is a link to the amplifier the cable company installed to cure all of my TV and Broadband issues.

http://www.extreme-broadband.com/amplifiers.html

 

[FIRE'd@51]

I'm pretty sure it would still be 3.5dB (50%) loss due to the hardware and connections inside. You should probably also put a 50Ω or 75Ω (depending on your system) termination on the unused port to keep RF reflections down.

I don't believe this is correct. If only one output is used the signal won't split in half because it would see essentially infinite impedance from the unused port, so very little (if any) of the signal would travel that way, leaving essentially 100% of the signal through the used port.

BTW 3db is a 50% reduction in power, not 3.5db.

 

[John Galt III]

I think my message said something "temporarily unavailable; be back soon"
Curious which channels have the problem. Mine was channels 1-20 and
> 90. The ones in between were fine. Don't understand why ....the lower channels were "local" stations.

For me, channels 2 through about 47 are fine, then I get some channels that are choppy, or don't come in at all (just get an error message). All the channels that are choppy or have error message are rare, sort of unknown channels like NASA, The Decade, Grit TV, etc. So it seems to me the signal from the cable company for those channels is low, or defective, for some reason. It's always the same channels that have the problem.

 

[John Galt III]

When the cable techs come out to fix the problem, do you get a service charge for it?

 

[kaneohe]

I don't believe this is correct. If only one output is used the signal won't split in half because it would see essentially infinite impedance from the unused port, so very little (if any) of the signal would travel that way, leaving essentially 100% of the signal through the used port.

BTW 3db is a 50% reduction in power, not 3.5db.

a contrary opinion from some tech forum:

ScottMac
Moderator<br>Networking<br>Elite member

The signal is split, whether you have a connection on the post or not. On a two-way splitter, you will lose more than half the signal automatically (the split, plus the "insertion loss").

https://forums.anandtech.com/threads/cable-modem-coax-cable-issues-through-splitter.1252812/

 

[Root]

I don't believe this is correct. If only one output is used the signal won't split in half because it would see essentially infinite impedance from the unused port, so very little (if any) of the signal would travel that way, leaving essentially 100% of the signal through the used port.

BTW 3db is a 50% reduction in power, not 3.5db.

This is not correct either. If you send 20dBmv of RF into a 2way splitter, the output(s) will be 16.5dBmv regardless if one output side is connected, terminated or left open, or both ports are used.

 

[John Galt III]

My cable is underground then comes above ground where it goes into a cable box on the outside of my house. Would they fish a huge length of coaxial cable from the street, under ground, and up to the side of my house? I ask because I saw the cable TV van outside the neighbor's house, and they had a huge length of black cable going all over the place, in the street, in his yard, but I couldn't tell where they were putting it. Maybe the neighbor had the same problem I have.

 

[euro]

My cable is underground then comes above ground where it goes into a cable box on the outside of my house. Would they fish a huge length of coaxial cable from the street, under ground, and up to the side of my house? I ask because I saw the cable TV van outside the neighbor's house, and they had a huge length of black cable going all over the place, in the street, in his yard, but I couldn't tell where they were putting it. Maybe the neighbor had the same problem I have.

Yes, they will do that if they determine that the signal that comes into the house is too weak compared to the signal up on the street. They just did that with mine - it's a 500ft run and they didn't hesitate at all. In fact, they put a temp overground cable and week later came back and buried the "final" cable. They offered the 500ft temp cable to me but I declined.... based on previous usage, it would take me about 1200 years to use up that much cable

 

[Koolau]

When the cable techs come out to fix the problem, do you get a service charge for it?

That is negotiable up front. When the nice young lady said that there would be a service charge for the cable guy to bring me an amplifier, I told her to connect me to the folks who could cancel my service. She said "Just a minute." When she came back on the line she said "There will be no charge for this service. We want you to be very happy with your cable experience..."

If you have to, mention to the nice lady you are thinking about "Direct TV". YMMV

 

[Peter]

Interesting question. So I measured it:

3dB splitter, both ports terminated, 3.6dB loss to each port. Why not 3.0dB? Because there are splitter losses, primarily in the coupling transformer.

As above, with one port open, the other terminated, 4.2dB loss to the terminated port. Where is the 'lost power' going? Actually, there is no lost power; the generator (or CATV system) is now mismatched, and is delivering less power to the splitter than before.

So the answer to the OP's question is that you need to remove the splitter to increase the signal level at your TV.

 

[Big_Hitter]

When the cable techs come out to fix the problem, do you get a service charge for it?

never - this is cableone

they also come out for free and put in wifi boosters all over the house for ya

 

[kaneohe]

Interesting question. So I measured it:

3dB splitter, both ports terminated, 3.6dB loss to each port. Why not 3.0dB? Because there are splitter losses, primarily in the coupling transformer.

As above, with one port open, the other terminated, 4.2dB loss to the terminated port. Where is the 'lost power' going? Actually, there is no lost power; the generator (or CATV system) is now mismatched, and is delivering less power to the splitter than before.

So the answer to the OP's question is that you need to remove the splitter to increase the signal level at your TV.

Thanks for your curiosity. Now I know the real answer!