Check Signal Levels

[SiJ2000]

Hi,

Just out of curiosity, what processes does the engineer go through to check the levels?

Do they just change the tap point in the cabinet to one with lower attenuation? I ask because my cabling is fine, it has just expanded with further services this year, therefore, there are splitters/isolators there which weren't there originally when we just had one box and the cable from the street going straight into it!

I have tested the cabling as I am an engineer (Data, not TV) and there is no unexpected attenuation/noise in the cabling...

Please let me know!

Thanks

S

[jb66]

In most areas yes, but in some telewest areas the network is set up for 3 devices, any less you attenuate any more and your either lucky and have enough signal or an hdu is fitted

[SiJ2000]

OK, Mine is an ex NTL area... I know the cab has different tap points for different levels of attenuation, but no idea which ones still have capacity or which one i'm in!!

Thansk

[pip08456]

OK, Mine is an ex NTL area... I know the cab has different tap points for different levels of attenuation, but no idea which ones still have capacity or which one i'm in!!

Thansk

Would you like to refine your question as I can't see what you are getting at.

Yes there's different tap point to enable the tech to adjust the attenuation on the line (basically just moving you to a different amp)

Does it matter which one you are in and if so how?

The capacity is the number of tap points-see above.

I just can't see where you are coming from.

I don't know if this will help but worth looking at seeing as you are interested

http://chriswoods.co.uk/2010/01/photos-inside-a-virgin-media-cable-street-cabinet/

[SiJ2000]

Hi,

That is interesting... I just have a concern as, whilst all my services are stable, my Upstream Power level is around the 55 mark and was one on 57!

I am just hoping that if it does get unstable and starts being troublesome in the future if they make any changes, that they aren't going to just recable my house, as those cables/connections/splitters are fine! They just never put me on a stronger signal when fitting extra splitters and boxes from the original single box with no splitter (cable in street straight through wall into STB!)

Thanks

Simon

[pip08456]

55dBv is getting towards the high side and as long as it doesn't fluctuate (as levels do) any higher is not a cause for concern. Once at 57dBv is right at the edge as your router is very nearly on the max but if an isolated case again not a cause for concern. It will be different if it happens on a regular basis.

Personnally I would like the signal more within the 40's to give leeway to any fluctuation up or down.

As 2nd line on the VM forum usually don't like a signal to be at 55 it may be worth posting there and reporting the change from 55 to 57 and they may get a tech out to do a minor adjustment.(they have the tools to check your connection online)

It will take up to 3 days for them to get to you
(from the date and time of last comment in thread you open )

Also have a look at Sephs post (must be OK Igni's not commented! :D) here (http://community.virginmedia.com/t5/Up-to-50Mb-broadband/POWER-LEVELS-amp-SNR-A-TECHNICAL-PRIMER/td-p/148072).

Forgot to add post your U/S,D/S stats and logfile too.

[SiJ2000]

Sorry, this is my current stats:

Downstream Lock : Locked
Downstream Channel Id : 56
Downstream Frequency : 298750000 Hz
Downstream Modulation : QAM256
Downstream Symbol Rate : 6952 Ksym/sec
Downstream Interleave Depth : taps12Increment17
Downstream Receive Power Level : -2.2 dBmV
Downstream SNR : 37.8 dB

Upstream Lock : Locked
Upstream Channel ID : 2
Upstream Frequency : 45800000 Hz
Upstream Modulation : QPSK
Upstream Symbol Rate : 5120 Ksym/sec
Upstream transmit Power Level : 54.7 dBmV
Upstream Mini-Slot Size : 1


What do you think? It's pretty consistent at this level... Went up to 57 last week when something changed (Maybe new UBR?) and my IP changed for the first time in months after an hours outage...

Thanks

Simon

[pip08456]

Sorry, this is my current stats:

Downstream Lock : Locked
Downstream Channel Id : 56
Downstream Frequency : 298750000 Hz
Downstream Modulation : QAM256
Downstream Symbol Rate : 6952 Ksym/sec
Downstream Interleave Depth : taps12Increment17
Downstream Receive Power Level : -2.2 dBmV
Downstream SNR : 37.8 dB

Upstream Lock : Locked
Upstream Channel ID : 2
Upstream Frequency : 45800000 Hz
Upstream Modulation : QPSK
Upstream Symbol Rate : 5120 Ksym/sec
Upstream transmit Power Level : 54.7 dBmV
Upstream Mini-Slot Size : 1


What do you think? It's pretty consistent at this level... Went up to 57 last week when something changed (Maybe new UBR?) and my IP changed for the first time in months after an hours outage...

Thanks

Simon


I would think (and don't quote me) that the outage and spike in upstream may have been due to perhaps work on the network in your area.

The change in IP can happen at any time as you do not have a static one although usually it will stay the same. It is not guaranteed though.

[SiJ2000]

Hmmm, went down again over night last night and now these are my figures:

Downstream Lock : Locked
Downstream Channel Id : 57
Downstream Frequency : 306750000 Hz
Downstream Modulation : QAM256
Downstream Symbol Rate : 6952 Ksym/sec
Downstream Interleave Depth : taps12Increment17
Downstream Receive Power Level : -2.8 dBmV
Downstream SNR : 38.7 dB

Upstream Lock : Locked
Upstream Channel ID : 2
Upstream Frequency : 45800000 Hz
Upstream Modulation : QPSK
Upstream Symbol Rate : 5120 Ksym/sec
Upstream transmit Power Level : 55.2 dBmV
Upstream Mini-Slot Size : 1

Again, perfectly stable etc, I am just concerned with all this going on that it's going to stop being stable if they are making changes as I don't have much contingency left!!

S

[pip08456]

I'm betting the upstream power level spiked again, you could really do with i looking at

[SiJ2000]

I might give it a couple of weeks then phone it in. I know the cabling is OK, so I suspect they just need to tap into a less attenuated point ijn the cabinet as I have splitters/etc which I didn't have before, having gone from just one V+ and Broadband in a single room where the cable came straight in, to 3 x V+, 1 x VBox and Broadband all going round the house!

Cheers

S

[Sephiroth]

It looks to me that there is attenuation on your line. Lowish DS and high US.

If nothing else is wrong, the engineer can move you to a lower attenuation tap point. The success of this would depend on where you're sitting now. From 29 to 22 dB would make your DS +4 and your upstream +48 dBmv which is OK; from 22 to 15 would have the same effect. From 18 to 15 would put your DS to 0 and US to 52 dBmv.

Thart sort of change might improve stability.

[SiJ2000]

Hmmm, without the modem even disconnecting/reconnecting (as no events in the event log), my stats are much better today!

Downstream Lock : Locked
Downstream Channel Id : 57
Downstream Frequency : 306750000 Hz
Downstream Modulation : QAM256
Downstream Symbol Rate : 6952 Ksym/sec
Downstream Interleave Depth : taps12Increment17
Downstream Receive Power Level : -2.7 dBmV
Downstream SNR : 39.4 dB

Upstream Lock : Locked
Upstream Channel ID : 2
Upstream Frequency : 45800000 Hz
Upstream Modulation : QPSK
Upstream Symbol Rate : 5120 Ksym/sec
Upstream transmit Power Level : 53.2 dBmV
Upstream Mini-Slot Size : 1

[SiJ2000]

Again without touching, but it resync'd over night, now look at the stats (much better again)!!!

Downstream Lock : Locked
Downstream Channel Id : 57
Downstream Frequency : 306750000 Hz
Downstream Modulation : QAM256
Downstream Symbol Rate : 6952 Ksym/sec
Downstream Interleave Depth : taps12Increment17
Downstream Receive Power Level : -1.9 dBmV
Downstream SNR : 39.3 dB

Upstream Lock : Locked
Upstream Channel ID : 2
Upstream Frequency : 45800000 Hz
Upstream Modulation : QPSK
Upstream Symbol Rate : 5120 Ksym/sec
Upstream transmit Power Level : 51.7 dBmV
Upstream Mini-Slot Size : 1

Could it be that changes can be made elsewhere downstream, or if they have, I assume that all my neighbours must have had an improvement too??

[Sephiroth]

Or something dried out in a pit, reducing attenuation slightly. So yes, something happened. But you'd need to check with your neighbours.

[SiJ2000]

Well they fixed something as the lowest it's EVER been was after install at 53!! Went up to over 57 at one point, then down to 52.7 and now 51.7...

Let's hope it stays... Even when it spiked at 57, it was never slower than 100% with no packet loss and minimal jitter all along. Guess I have been VERY lucky!! ;)

[Sephiroth]

Rather lucky, I'd say. DOCSIS is designed for this. High attenuation can be overcome by upstream power and provided it's reasonably stable (i.e. not stepping up at 0.25 intervals every 5 seconds - which is usually a noise problem), then you'll have no worse a problem than your neighbour, if any.