ntl250, low/high signal levels

FireFoxx80 · 17-11-2006, 11:59

Hi there,

First time poster (seems original post was eaten), but this forum seems very informative. Helped me out once already.

Over the last 3 weeks I have had increasing packet loss on my 5+yr old Terayon modem. The only pattern to this was that the packet loss was in proportion to usage (4MB connection). Packet loss was about 8-12%, occurring in chunks rather than intermittent loss.

I saw the sticky about Terayon's and QAM256, so I phoned ntl to report the fault and they sent an engineer around to replace the modem.

So, engineer arrives yesterday to install modem. Swaps the modem out and installs a new ntl250 modem. Whilst he's there, he also says that my signal levels are too high, and could be what's causing the problem; so he also sticks two attenuators/forward pass equalizers on both my ntl250 modem and my digibox. I am not 100% sure of the combination as I only realised the problem this morning. The engineer also went out into the road to fiddle with the box to change something.

This morning I wake up to no net connectivity at all, not sure about digital TV signal, the box was reporting it had a channel at least (not stuck on tune/boot). I check the modem diagnostics and it reports a downstream of about 28dB and an upstream of about 61dB. And although it can lock onto a downstream, it fails on the upstream and goes into a continuous reboot cycle.

Anyway, I phone ntl and they say that my signal levels are now "through the floor". The soonest they can get an engineer out is next Thursday (Saturday as I cant take time off work). The guy on the phone suggests I can try messing with the attenuators, but might not help.

So, any suggestions?

Edit: Sorry mods, as I say, first post eaten (prolly me not seeing preview/post difference this early in morning), made test post to see if acct was/wasn't restricted.

**Chris** · 17-11-2006, 12:02

Your first post said 'test, sorry, please ignore' ... I eat posts like that for elevenses.

to the Forum. I never had an attenuator on my cable modem or STB, but have a look at the ones on yours and if you think you can get them off and on again without damaging anything, then I don't see why you shouldn't try, especially if the CSR suggested it. If you break something you can always blame them ...

FireFoxx80 · 17-11-2006, 18:50

Resolved (I think)

ntl engineers had put two attenuators on the digibox, and a single 4dB one on the cable modem.

Before:
DownStream -4.5
DS SnR 24.3
Upstream 46 to 61 fluctuating

No connectivity with this setup.

After removing attenuator:
DownStream -3.0 to -3.3
DS SnR 41.0
Upstream 55.5

Working for now, no aparrent packet loss yet.

Still going to keep engineer booked and see what it's like after a few days. Fingers crossed it is fixed now.

Nedkelly · 17-11-2006, 19:19

The problem is with your upstream 60 to 61 dbmv is way to high .A tech can not test this with the standard meter issued .A tech vist is needed as if left you modem will keep dropping the conection .Hope this helps

jaycee · 18-11-2006, 04:19

55dBmV upstream power is still pretty high, but if it holds steady and the downstream SNR stays at 41dB (a very good figure), i'd leave it at that.

Attenuators are typically for capping DOWNSTREAM power levels usually when it's like +5dBmV or greater. If the engineer went and upped the gain in the cabinet he shouldn't have installed attenuators!