1 ACCEPTED SOLUTION
Accepted Solutions
Ok, your downstream signal levels are still too high, but, the question is, are you seeing any issues with downstream data or disconnects. If not, then the best solution is to leave it alone. You don't need the amplifier. Disconnect it and put it aside just in case you decide to use a MoCA network at some point in the future.
The best solution for this is to install a Forward Path Attenuator to drop the downstream signal levels That attenuator will drop the downstream signal levels and leave the upstream levels where they are. Here's an example:
https://www.amazon.ca/line-Signal-Forward-Attenuator-FPA6-54/dp/B07882H96R
That's a 6 dB Forward Path Attenuator. The better solution would be a 9 dB Forward Path Attenuator, but, that looks to be fairly expensive. So, I'd go with a 6 dB Forward Path Attenuator if I really wanted to do something about this.
https://www.amazon.ca/FPA9-54-Forward-Attenuator-DOCSIS-Cable/dp/B08DMBWG8Q
I don't believe that Rogers techs carry Forward Path Attenuators in their vans. I suspect that they would only have the normal attenuators on hand which drops the downstream signal level but ends up pushing the upstream signal level by the same amount. That's not a great solution unless you have sufficient upstream room between the upstream signal level and the max output level of 51 dBmv. If you were to install a normal 6 dB attenuator you would end up with approx 3 to 4 dBmV for the downstream levels and approx 45 dBmV for the upstream levels, which is still acceptable. Ideally one would drop the downstream signal levels down to 0 dBmV, but, using a conventional attenuator, you would end up with the upstream signal levels around 48 to 49 dBmV, which is too close the max output limit of 51 dBmV for my liking. Overtime, as the external cable and its connectors age, the downstream levels naturally drop due to cable losses, and the modem output levels are commanded to increase in order to arrive at the CMTS within the required specs. Running at 48/49 dBmV before that starts is looking for trouble at some point in the future. When the modem reaches its max output levels, its starts to drop upstream channels one by one in order to use the max output power across fewer channels. That will happen channel by channel as required. When you're at that stage, you will know it as the data rates will drop due to the loss of one or more upstream channels.
If you had a splitter on hand, either a two port or a multi-port splitter you could use that temporarily as an attenuator. Its not an ideal solution, but it would work. A two port splitter drops the signal level by 3.5 dB, a multi-port splitter will usually have one port dropping 3.5 dB, and two or more ports dropping 7 dB. You could use the 7 dB port for an experiment. With either of those in place, you would see the difference in the signal levels at the modem. The splitter isn't ideal as the unused ports should have a 75 ohm terminator installed to prevent any internal signal reflection back down the cable system. They look like this:
Hope this helps. As they say, if it ain't broken, don't fix it.
Of note, you have two DOCSIS 3.1 downstream OFDM channels running, so, I'd expect pretty good downstream performance. DOCSIS 3.1 upstream isn't running on your modem. That has to be enabled at the CMTS, so, its most likely that your CMTS isn't running DOCSIS 3.1 upstream for any of it's connected neighbourhood nodes.
@amd7674 your DOCSIS 3.0 downstream channels (1 to 32) are too high. They should all be centred around 0 dBmV with a signal to noise ratio of 36 to 40 dB. The upstream DOCSIS 3.0 channels (1 to 4) should be running in the 36 to 40 dBmV range.
Can you bypass the amplifier and post the signal levels. After you bypass the signal levels, restart/reboot the modem, then copy the signal levels.
Without any other devices, such as Nextboxes or Home Phone modems in the local cable network, you probably don't need the amplifier. The signal levels will show if that's the case.
Ok, your downstream signal levels are still too high, but, the question is, are you seeing any issues with downstream data or disconnects. If not, then the best solution is to leave it alone. You don't need the amplifier. Disconnect it and put it aside just in case you decide to use a MoCA network at some point in the future.
The best solution for this is to install a Forward Path Attenuator to drop the downstream signal levels That attenuator will drop the downstream signal levels and leave the upstream levels where they are. Here's an example:
https://www.amazon.ca/line-Signal-Forward-Attenuator-FPA6-54/dp/B07882H96R
That's a 6 dB Forward Path Attenuator. The better solution would be a 9 dB Forward Path Attenuator, but, that looks to be fairly expensive. So, I'd go with a 6 dB Forward Path Attenuator if I really wanted to do something about this.
https://www.amazon.ca/FPA9-54-Forward-Attenuator-DOCSIS-Cable/dp/B08DMBWG8Q
I don't believe that Rogers techs carry Forward Path Attenuators in their vans. I suspect that they would only have the normal attenuators on hand which drops the downstream signal level but ends up pushing the upstream signal level by the same amount. That's not a great solution unless you have sufficient upstream room between the upstream signal level and the max output level of 51 dBmv. If you were to install a normal 6 dB attenuator you would end up with approx 3 to 4 dBmV for the downstream levels and approx 45 dBmV for the upstream levels, which is still acceptable. Ideally one would drop the downstream signal levels down to 0 dBmV, but, using a conventional attenuator, you would end up with the upstream signal levels around 48 to 49 dBmV, which is too close the max output limit of 51 dBmV for my liking. Overtime, as the external cable and its connectors age, the downstream levels naturally drop due to cable losses, and the modem output levels are commanded to increase in order to arrive at the CMTS within the required specs. Running at 48/49 dBmV before that starts is looking for trouble at some point in the future. When the modem reaches its max output levels, its starts to drop upstream channels one by one in order to use the max output power across fewer channels. That will happen channel by channel as required. When you're at that stage, you will know it as the data rates will drop due to the loss of one or more upstream channels.
If you had a splitter on hand, either a two port or a multi-port splitter you could use that temporarily as an attenuator. Its not an ideal solution, but it would work. A two port splitter drops the signal level by 3.5 dB, a multi-port splitter will usually have one port dropping 3.5 dB, and two or more ports dropping 7 dB. You could use the 7 dB port for an experiment. With either of those in place, you would see the difference in the signal levels at the modem. The splitter isn't ideal as the unused ports should have a 75 ohm terminator installed to prevent any internal signal reflection back down the cable system. They look like this:
Hope this helps. As they say, if it ain't broken, don't fix it.
Of note, you have two DOCSIS 3.1 downstream OFDM channels running, so, I'd expect pretty good downstream performance. DOCSIS 3.1 upstream isn't running on your modem. That has to be enabled at the CMTS, so, its most likely that your CMTS isn't running DOCSIS 3.1 upstream for any of it's connected neighbourhood nodes.
@amd7674 those attenuators don't look like Forward Path Attenuators. Here's a link to a PPC spec sheet that shows the attenuator numbering scheme:
That attenuator that is shown on the spec sheet is probably the ideal attenuator for your situation. Its an FPA10-54. that is a 10 dB attenuator that starts at 54 Mhz and goes upwards from there. Its too bad that the spec sheet doesn't show the performance above 860 Mhz, although I wouldn't expect much difference, if at all above 860 Mhz.
Looking around, all I've see are attenuators that start at 5 Mhz, instead of 54 Mhz which is where the PPC Forward Path Attenuators start. So, my choice at this point would be the PPC Foward Path Attenuators. Don't know where to find them however as they don't seem to show up in a search. I suspect that a cable supply company would have them on hand, just a question of whether or not their available for retail customers.
Here's a link to the PPC residential products:
https://www.ppc-online.com/solutions/premises
Expand the product type and select "Attenuators".
Not a stupid question at all. 2 attenuators as indicated would work. Ideally you would be at 0 dBmV or just slightly above. When the next firmware version, 7.2.4.1.4b15 is loaded you will be able to keep track of the corrected and uncorrected codewords for the DOCSIS 3.0 downstream channels. With those numbers available, you can run an experiment, one attenuator versus two, and compare the codeword numbers after a set period of time. That should be the arbiter of which configuration works best.
You should install the attenuators at the modem, so that the signal level remains high until it hits the attenuator(s). That should keep any noise down to a minimum, which should be reflected in the codeword numbers.
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