Observer

Re: Only 4 downstream channels: My modem supports 8.

I think you're saying that in the future, the modem could pick up a downstream channel below 550 Mhz since channels 13 (531 Mhz) and above have a QAM256 signal and that would reintroduce high bit errors.  The upstream power level seems low according to internet wisdom but I don't know how to measure the upstream error rate from the modem.

 

All our utilities are underground including the cable.  The main cable in the neighborhood was upgraded about a year ago and the 4 downstream channel problem started maybe 2 months ago.  Before the 4 DS channel problem and after factory reseting the modem, speed test results have been consistently > 100 Mbps.  I attached a picture on the cable connection with an in series device marked FBR 3/73.

 

FBR 3/73FBR 3/73TerminalTerminal

Expert

Re: Only 4 downstream channels: My modem supports 8.

2 things wrong.. There's 3 ports in the pedestal that don't have terminating resistors in them and there indeed is a filter trap on your line that needs to be removed.

Very sloppy work by whoever replaced that Tapoff. with missing terminators and if all in the neighborhood are like that, it's no wonder levels are off.

 

Expert

Re: Only 4 downstream channels: My modem supports 8.

A FBR 3-73 blocks cable channels 3-73 ( 54-517 mHz) with >50 dB of isolation that rolls off to 0 dB at 550 mHz

 

Observer

Re: Only 4 downstream channels: My modem supports 8.

I have two questions.  One, the Antronix Milenium Series Multi-tap 2414 doesn't indicate if a termination resistor is recommended.  If the coax terminal has DC voltage then a termination resistor would not be used.  Two, the cable mdem termination system hands out the downstream channels.  Is it possible the CMTS was replaced without factory resetting the cable modem and that caused the wrong DS channels to be active?

Expert

Re: Only 4 downstream channels: My modem supports 8.

ALL F CONNECTORS MUST HAVE TERMINATING RESISTORS ON THEM TO BALANCE THE PORTS THAT ARE IN USE.

 

That aluminum can at the pedestal is the issue, it needs to be removed.  With the amount of corrosion, it's also the probable broadcast TV ingress point

TWC/ SPECTRUM has NO RECORDS on who has what filter traps in line or which ones.... There are people that still have 20 year old "showtime/HBO single channel traps that cause a myriad of issues.

 Phone support has no clue, the level drop offs are a dead giveaway.

They added the lower channels 2 years ago and the day they did it in Austin, there were near 5-10,000 internet only customers that had issues, took them 2 months to remove the wrong filters and they still show up today. NC/SC was the same but with a lot fewer filters. I think they were replacing the ch 3-73 traps with ch 3-60 ones... In some places they used 3-65's and ch 62 on up were used for modems...

Serious lack of engineering.  Phone support was even worst, refusing to send out techs because customers sorta worked, denied there were any filter traps.. I spent a couple hours on the phone with them to get this resolved, was on with an actual tier 4 perdson to get the techs dispatched properly in Austin... as well as the TX BBB/ cable tv comission.

This is not a CMTS or modem issue, they assigned channels and assumed there were no trapped out channels.

 

 

 

Observer

Re: Only 4 downstream channels: My modem supports 8.

A big thanks to everyone who responded to this message.  It quickly allowed me to work around and understand an intermittent internet speed issue I was having.  The final step is getting Charter/Spectrum to fix the signal levels and update the channel trap.  However, I've moved to fiber, partly due to this issue and partly due to price, so I'll tackle that step if I return to cable internet.

Expert

Re: Only 4 downstream channels: My modem supports 8.


sunnyrunner wrote:

I have two questions.  One, the Antronix Milenium Series Multi-tap 2414 doesn't indicate if a termination resistor is recommended.  If the coax terminal has DC voltage then a termination resistor would not be used.

 

there is 90 vac on the hardline only.  

 there is nothing on the F connectors and it's assumed the technicians are smart enough to terminate all unused ports as open/ noisy ones affect all the other ports. They use the security ones so that customers can't add in pirate hookups.

 

The hardline 75 ohm terminators have a blocking capacitor in series with the 75 ohm resistor to prevent it from becoming a heating element, lol.


 

Established Sharer

Re: Only 4 downstream channels: My modem supports 8.

You're smart enough to know how to remove the trap 'as an experiment' and see whether your DS signal levels return to normal (between -8.0 to +10.0 dBmV and SNR of 35 dB or better).  It would save the home service tech one step during his next visit, but if you've transitioned to delivery over fiber there's no benefit for you in doing that.  

Expert

Re: Only 4 downstream channels: My modem supports 8.

his pedistal is a disaster and needs a competent tech to term the 3 unused ports, remove the trap and replace the F connector.

Many of the traps have hi vswr on the trapped out frequencies and affect other users on the tapoff as well. Since TWC/Spectrum has gone all encrypted qam for video, there's no longer need for the traps/filters.  only one would be a 1ghz lpf/ poe/moca one for WHdvr and MOCA distribution inhouse

those big filters are garbage, they aren't potted solid, suck in moisture and corrode

 

Established Sharer

Re: Only 4 downstream channels: My modem supports 8.

Agreed.  And the right place for a MOCA filter is on the customer side of the grounding block, preferably indoors on the splitter.