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Old 09-08-2006, 20:00   #3
sollp
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Join Date: Mar 2005
Location: here
Age: 55
Services: Virginmobile,Sky TV, ZEN 76Mb,ZEN Phone line.
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Re: Return path problems?

Quote:
Originally Posted by MrDuck
Hi,

I've had BB disconnects happening continuously for approx. 6 months.

So far:

1. New external cable pull - RG11 - ~90m
2. New internal cabling - RG6 (i think)
3. Ambit (NTL 250) modem (same as original) replacement - same problems

I have to connect directly to the incoming coax, without a splitter (to STB) to get some sort of BB service. It will stay up for undetermined periods with usually one or two disconnects per day - sometimes down for hours at a time.

I have tried 3 types of NTL splitter: 3.5 dB (red writing on label), 3 dB (blue writing - from memory - engineer took this one back, so can't confirm) and an isolated 2 way (green label, chunky). I also now have a 6dB forward path attenuator, square type, FLD5W (not currently used). Any splitter in the signal path kills my BB. The FP attenuator does not seem to greatly affect the uptime of the modem, when used.

Here are stats from modem - note upstream power level:

Downstream Lock : Locked
Downstream Channel Id : 2
Downstream Frequency : 586750000 Hz
Downstream Modulation : QAM64
Downstream Symbol Rate : 6952 Ksym/sec
Downstream Interleave Depth : taps12Increment17
Downstream Receive Power Level : 5.4 dBmV
Downstream SNR : 33.4 dB

Upstream Lock : Locked
Upstream Channel ID : 6
Upstream Frequency : 22000000 Hz
Upstream Modulation : QPSK
Upstream Symbol Rate : 2560 Ksym/sec
Upstream transmit Power Level : 61.0 dBmV
Upstream Mini-Slot Size : 2

It looks like a return path issue to me. We also have no return path on the STB when connected. My immediate neighbour noticed that his return path has not been available since a local TV and BB outage a few weeks ago. We have updated STBs for interactive services and are serviced by Bromley.

I have also been told by TS (UK) that the UBR has low utilisation (~13%).

I have an engineer coming out on Saturday and would like to make sure that he checks the cabinet equipment. Should I ask him to check the 'Return Path Modulator and Amplifier' as per:

http://www.cableforum.co.uk/board/sh...hlight=cabinet

?

Not sure if the 'normal' engineers have the ability to repair cabinet equipment so would like to check. Will the engineer have to make a request back to NTL to get another (network) engineer out to fix cabinet equipment? I have not got any reasonable info back from TS (UK or India) on this question.

Any help would be greatly appreciated as this is now driving me nuts! The last engineer said that he did not know what the problem was when the modem failed to come up - should he have tried to diagnose the problem from the cabinet? or is that left up to somebody else?

Thanks
Yes it is a return path issue/problem. Your transmitting at 61dB this is to high ideally you should be no more than 55dB at the very most. Your connection is dropping out because of this. Why they haven't seen this on previous visit's i don't know. I know they do not have the correct test equipment but a quick look on the STB engineering screens or log into the modem would have flagged this problem before now. They need to come back test to see if it is a network fault and get it passed over oto the network guys if it is, pronto!
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