OFDM errors

all of my channels are working fine except the OFDM channel. Can someone shine some light as to what the problem maybe?. When the Xfinity Technician came he ran a new line from the pedestal up to the modem . However he put a splitter in between so don't know if this could be the cause.

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Accepted Solution

EG

Expert

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110.3K Messages

2 years ago

The upstreams are much better ! Now there is plenty of wiggle room. The downstreams are higher (especially at the higher channels) approaching out-of-spec levels. It's always a balancing act with splitters ! This could go either way. Leave it out for now and see if you have any connection problems. Live with it for a few days. If problems arise you can always put it back in the line.

(edited)

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jsc305

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9 Messages

@EG question. What should be the acceptable parameters for the down and upload stream. Also the internet bounced so I had to put the splitter again. However , in the splitter there is the in and out connection. one is -3dB and the other is -7dB. which one should I put it in?

2 years ago

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EG

Expert

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110.3K Messages

Here are the Comcast spec signal values from the pinned Self Troubleshooting Tips topic at the top of this board's page;

Specification	Min	Max
Downstream Power Level
Cable Modems	-10dBmV	+10dBmV
Gateways and EMTAs	-7dBmV	+7dBmV
Downstream Signal to Noise Ratio	35dB	-
Upstream Power Level	+35dBmV	+50dBmV
Upstream Signal to Noise Ratio	31dB	-
Upstream Receive Power	-2dBmV	+2dBmV

The -3 dB port has less insertion loss than the -7 dB port. But if line attenuation is indeed needed, a splitter should not be used for that purpose. The right tool for the job should be used. In this case, a -6 dB FPA ( Foward Path only Attenuator) such as the one in the link below would appear to be the right fit;

https://www.amazon.com/FPA6-54-Forward-Attenuator-DOCSIS-Internet/dp/B08KTRC3XZ

It will knock down that hot downstream power by 6 dB, but it won't affect the upstream power which will be good / in spec.

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2 years ago

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EG

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110.3K Messages

2 years ago

The OFDM channel is a very wide bandwidth channel that packs a lot of data within. Due to that fact, seeing a large number of corrected errors is normal. The FEC (Forward Error Correction) circuitry / system is doing its job. The vast majority of those errors are *corrected* ones. There are very few *uncorrected* errors in comparison !

Are you actually experiencing any connectivity / performance problems or are you just focusing on those bit errors on that channel ?

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jsc305

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9 Messages

@EG not seeing any issues but was curious if this was a normal pattern. Also there's nothing connected to the splitter other than the cable coming from outside and going to the cable modem. Should I remove the splitter or leave it?

2 years ago

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EG

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110.3K Messages

2 years ago

First. What do the upstream power level values look like ? The downstream power is good as are the SNR values.

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jsc305

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9 Messages

2 years ago

is this what you were asking for?

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EG

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110.3K Messages

2 years ago

Those are approaching the high / marginal side. Take the splitter out and post what the power levels look like then.

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jsc305

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9 Messages

@EG without splitter. Also this is an Arris S33 brand new modem. Just installed it last week. Looks like the numbers came down

2 years ago

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EG

Expert

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110.3K Messages

2 years ago

How 'bout the downstreams ?

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jsc305

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9 Messages

@EG

here you go. Didn't see much of a change

2 years ago

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OFDM errors

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