Request for help to check my modem Signal Levels

[Ziggi]

Hi Guys got a problem with our modem (NTL)Ambit 250 it will lock and work fine some days all day but other days i've gotta reset it loads, When it stops working I get the ready light flashing

Here are the modem configuration info I grabed we are on 20mb

Acquire a Downstream Channel 459000000 Hz Locked
Connectivity State OK Operational
Boot State OK Operational

Network Access : Allowed
Maximum Downstream Data Rate : 20480000
Maximum Upstream Data Rate : 768000
Maximum Upstream Channel Burst : 3044
Maximum Number of CPEs : 1
Modem Capability : Concatenation Enabled, Fragametation Enabled, PHS Enabled

Downstream Lock : Locked
Downstream Channel Id : 52
Downstream Frequency : 459000000 Hz
Downstream Modulation : QAM64
Downstream Symbol Rate : 6952 Ksym/sec
Downstream Interleave Depth : taps12Increment17
Downstream Receive Power Level : -5.2 dBmV
Downstream SNR : 29.2 dB

Upstream Lock : Locked
Upstream Channel ID : 3
Upstream Frequency : 47400000 Hz
Upstream Modulation : QAM16
Upstream Symbol Rate : 2560 Ksym/sec
Upstream transmit Power Level : 42.5 dBmV
Upstream Mini-Slot Size : 2

would appreciate if anybody could point out what the problem of the ready light flashing and no access is to forward onto VM:mad:

thanks in advance ;)

[Sephiroth]

Your SNR at 29.2dB is too low. For a 20Mbps service, you should be modulating at 256QAM not 64QAM. So the service has "reverted" to something that is more useable with that poor SNR.

The causes of poor SNR could be a misfunctioning modem; coax not properly screwed in at either end; water in the external wall box; some mis-connection at the street cabinet or anywhere else (in which case your neighbours would have a problem too).

So, internal stuff to check then if not fixed, a call after 08:00 to VM services.

[Ziggi]

Ok Thankyou Sephiroth will give me a few things to check I do have a long Coax inside that maybe got damaged

but i did see VM vans few weeks ago messin with the local Street cabinet and since then i belive the problems have started,

Is there anyway to check these Configurations on my sammy v+ box as thats on its own Coax and pretty short ?

Thanks again

[Sephiroth]

Good idea.

Yes there is a menu item (which I forget and |I'm not at home right now so can't check). I think it's marked Maintenance or something. I'm fairly sure the info's in the V+ section of this forum.

[Ziggi]

I think I found it via Home - 8 Settings - 6 Technical Stuff - down a page

SNR 34.0dB

whats the range at which I should recive if you dont mind me asking :)

[Peter_]

Your SNR at 29.2dB is too low. For a 20Mbps service, you should be modulating at 256QAM not 64QAM. So the service has "reverted" to something that is more useable with that poor SNR.
.
The SNR is low but the Langley and Bromley platforms do use 64QAM for 20Mb and 50Mb.