125M : Exposed VM coax cable in junction box

[Sephiroth]

That means the amplifier is out of slope - but not so as to worry. The SNR is poor though although not far from being in the optimum range.

The SH in modem mode would eliminate the VMNG300 being on the way out.

[Eeeps]

Originally Posted by Sephiroth

That means the amplifier is out of slope - but not so as to worry. The SNR is poor though although not far from being in the optimum range.

The SH in modem mode would eliminate the VMNG300 being on the way out.

I'm not sure it's the amp characteristics. Here are my five down stream...

Locked 140 290750000 Hz QAM256 3.8 dBmV 43.2 dB 4730 25
Locked 141 298750000 Hz QAM256 3.9 dBmV 43.2 dB 4548 12
Locked 142 306750000 Hz QAM256 3.8 dBmV 43.2 dB 4513 11
Locked 143 314750000 Hz QAM256 3.7 dBmV 43.2 dB 4625 17
Locked 144 322750000 Hz QAM256 4.2 dBmV 43.9 dB 1304 0

The first four were the originals and the fifth was added about 4 months ago. This has about 0.5dB higher amplitude and 0.7dB better SNR.
My guess is that this fifth channel is provisioned from a different line card in the CMTS.

[Sephiroth]

I didn't say the amp characteristics were a cause of the OP's problem.

But looking at your stats, Eeeps, or rather your closing statement - the fifth channel MUST be on the same line card as the others. You are terminated on one line card, not on two. Generlly speaking (but not mandatory in DOCSIS 3), downstream channels 2 onwards are separated by 8 MHz bandwidth, which is your case. The fifth channel arises becasue VM are load balancing across as many downstream channels as are available to a network segment and which have high SNR.

[jb66]

Originally Posted by Sephiroth

That means the amplifier is out of slope - but not so as to worry. The SNR is poor though although not far from being in the optimum range.

The SH in modem mode would eliminate the VMNG300 being on the way out.

How can you tell if its out of slope? there all mid range frequencies shown

[Sephiroth]

Originally Posted by jb66

How can you tell if its out of slope? there all mid range frequencies shown

Frequency 299000000 307000000 315000000 323000000
Power Level(dBmV) -1.05 -0.40 -0.53 -0.59
RxMER(dB) 34.48 33.38 34.48 34.93

Because attenuation increases with frequency, the huighest power level should be at 299 MHz, not tbhe lowest

But it's not out in a link destroying manner. Just an observation.

[jb66]

I thaught you were looking at that.

The amp may still be sloped correctly but the lenth of the cable and the thickness of it determines the outcome at the house.

For example the 411 frequency may be 15db on a tap and 691 shoukd be higher say 20db. After 60m or so at the end of he drop you find that 411 is 4db but 691 is 0db.

So if the op above is close to the amp then the highest frequencies should be higher than the low as that's the way the amp is set up and the cable isn't long enough to even them out.

Anyway it's 0.5db and it will be playing no part in the issue

[qasdfdsaq]

Originally Posted by Sephiroth

But looking at your stats, Eeeps, or rather your closing statement - the fifth channel MUST be on the same line card as the others. You are terminated on one line card, not on two.

Actually it doesn't have to be part of the CMTS at all or even in the same building, VM have used E-QAM architectures in some places IIRC.