100M Signal Levels - Page 2

jb66 · 06-09-2011, 13:26

It should be between -3 and +6. Time to email CEO office

RB2004 · 06-09-2011, 13:57

Quote:

Originally Posted by jb66

It should be between -3 and +6. Time to email CEO office

Hi, after the engineer left, I phoned back the 100mbit team, logged into my computer remotely and done some speed tests on the virgin media website and even he couldnt get more than 55mbit at that moment in time.. also showed him my previous speed tests which showed a fluctuation in speeds 1 minute 96, then maybe 80, then 74, back up to 96 then down to 50 etc lol very erratic.. and his answer was to send out another superhub for what good that will do... im going to be back on the phone no doubt...

regarding the CEOs office, I actually emailed them first originally because i was fed up of this 6 year ongoing issue of weak/borderline signals. all they did was send down an engineer, the first one.. and he did sod all... just told me RG11 was a london architecture, moved my line on the taps and said about the corrosion in the pit before promptly leaving.

Then when he did nothing I phoned retentions, threatened to leave and they booked me a cable repull... which was cancelled because the area manager thought it un-necessary, that was when the 100mbit team said -6 dBmV was borderline and sent this engineer.. but hes turning around saying -7 dBmV is borderline as problems wont occur until it hits -7.1 dBmV, and -6 dBmV is fine.. and after phoning back 100mbit team they dont want to argue with this engineers verdict.

Just seem to be going around in circles now. This engineer told me im the only person on this particular tap.. which means the signal coming out must be ok... and probably for normal customers with maybe 1-2 boxes and a modem is adequate... but because I have 3 boxes, and a modem... 4 way spliiter outside (3outputs, 1 input) and a 3 way splitter inside (2 outputs, 1 input) to split for modem and V+ my signal is significantly weakened.. and even if im only loosing 2-3 dBmV over the cable its enough to make my signal levels borderline.

---------- Post added at 12:57 ---------- Previous post was at 12:45 ----------

It occurs to me, that a lot of these engineers know I need a repull, but they cant do anything more themselves because im already on the highest tap, and the only cable on that tap. which is why they arent doing anything just leaving.

But nobody will recomend a repull because they know I wont get one so its easier for them to fob me off with excuses.

Just lost for ideas now.

Sephiroth · 06-09-2011, 14:07

There's a reasoned explanation of attenuation between street cabinet and cable modem here.

How far are you from the street cabinet? There are attenuation points of 12, 15, 18 & 22 dB (if my memory serves me correctly) from which an engineer can choose for your case. So the highest leaving the tap point would be c. 30 dBmv (see the article) and then the losses on the way.

jb66 · 06-09-2011, 14:18

Did you mention an HDU if they refused RG11? That will boost your downstream by 6db as they would remove the 3 way spitter and if they wired it properly removing the 2 way splitter you'd actually gain 10db

Sephiroth · 06-09-2011, 14:27

JB - have you done these before? Like come straight into the house from outside and do the HDU inside, avoiding the outer wall box and connections?

RB2004 · 06-09-2011, 14:34

Quote:

Originally Posted by Sephiroth

There's a reasoned explanation of attenuation between street cabinet and cable modem here.

How far are you from the street cabinet? There are attenuation points of 12, 15, 18 & 22 dB (if my memory serves me correctly) from which an engineer can choose for your case. So the highest leaving the tap point would be c. 30 dBmv (see the article) and then the losses on the way.

I will have a go at estimating the distance and get back to you. must be about 100 metres total cable length give or take a few metres by the time you go from the brown box to the pavement, then down the street to the pit, then accross the road from the pit to the green cabinet which is in line. Might actually be less, which is why they arent giving me the RG11, but with the 2 splitters, 3 boxes and modem plus the signal drop on the cable alone its pushing my signal too weak.

if there is a 22 dB attenuation point, surely it shouldnt end up at -6 dBmV

I know I have 2 splitters on the line, the 4 way with 3 outputs, and a further 3 way with 2 outputs connected to one of the ways on the 4 way.

but ok, deduct 6 dBmV roughly for those splitters but surely on a 22 dB attenuation point I should be getting a better signal than that.

I had a look at the link posted on the VM website you referenced.

It does clearly say,

QAM256 -3 dBmv to +7 dBmv

So why is the 100mbit team telling me they wont argue with the engineers verdict, that -6 dBmV is fine, and the engineer saying he wouldnt be worried unless it is -7 dBmV? is this some kind of lack of traning or knowledge or something?

---------- Post added at 13:34 ---------- Previous post was at 13:32 ----------

Quote:

Originally Posted by jb66

Did you mention an HDU if they refused RG11? That will boost your downstream by 6db as they would remove the 3 way spitter and if they wired it properly removing the 2 way splitter you'd actually gain 10db

Yep, he wasnt interested.. just kept saying signal levels are fine, as they are above -7 dBmV and that i wont have problems unless it drops to - 7.1 dBmV

lol, the amount of hastle this is creating, just to get it fixed it makes you wonder if its easier to just open up the pit one night when nobody is around and have a go moving yourself onto another tap... even though im sure thats highly illegal so i wont be doing that.

Sephiroth · 06-09-2011, 14:54

It wasn't so much the -3 to +7 I was recommending to you. It was the 100 metre calculation of signla loss depending on the tap point you're on. You'd have to go to the cable type (e.g. RG11) web sites to get the attenuation calculation per metre at 400MHz.

Personally I have no doubt that -7 dBmv would be somewhat problematic.

BTW, Masque of VM has posted -3 to +7 in this forum as the optimal 256QAM downstream power levels.

jb66 · 06-09-2011, 15:02

You can get internal hdu and external, the internal has 1 input 4 outputs and 1 for the plug. Ok so your modem says -7 thats at mid range, your high frequencies are going to be near -15 as high frequencies drop of more.

RB2004 · 06-09-2011, 15:08

Quote:

Originally Posted by jb66

You can get internal hdu and external, the internal has 1 input 4 outputs and 1 for the plug. Ok so your modem says -7 thats at mid range, your high frequencies are going to be near -15 as high frequencies drop of more.

Yep, thats about right because if I can remember, my V+ box signal levels on the one downstairs with the modem on the same splitter... the signal levels are as low as -12 dBmV

Sephiroth · 06-09-2011, 15:15

Quote:

Originally Posted by jb66

You can get internal hdu and external, the internal has 1 input 4 outputs and 1 for the plug. Ok so your modem says -7 thats at mid range, your high frequencies are going to be near -15 as high frequencies drop of more.

I hadn't thought of that. The SNR at the modem is an estimate after demodulation.

For my mathematical mind (and the attenuation tables, of course, where do you put "mid range" as a frequency point?

jb66 · 06-09-2011, 16:11

I usually test 104mhz for low 323, 331 for mid and 619 and 691 for high. A drop of 100m will seriously hamper your high frequencies, that's why rg11 is a better solution than an hdu.

RB2004 · 06-09-2011, 16:15

Quote:

Originally Posted by jb66

I usually test 104mhz for low 323, 331 for mid and 619 and 691 for high. A drop of 100m will seriously hamper your high frequencies, that's why rg11 is a better solution than an hdu.

any sugestions on how I can force an RG11 pull? lol

because im being told no i cant have one, and when i did manage to get one booked the area manager cancelled it as he said it was not necessary.. no idea how he came to that conclusion though nobody came to check out my setup, or signal levels on each device.

jb66 · 06-09-2011, 17:21

You shouldn't have to, you should ask the engineer to fix your net then let him work out the how

RB2004 · 06-09-2011, 18:45

Quote:

Originally Posted by jb66

You shouldn't have to, you should ask the engineer to fix your net then let him work out the how

lol, I have, ive had 2 engineers down, who have done nothing and walked away, the latter thinking -7 dBmV is acceptable. As far as they have been concerned there is no problem.

RB2004 · 09-09-2011, 15:01

latest signal levels as of today.

Locked QAM256 194 55616000 Kbits/sec 299000000 Hz -6.4 dBmV 38.7 dB Hybrid
Locked QAM256 193 55616000 Kbits/sec 291000000 Hz -6.1 dBmV 38.2 dB Hybrid
Locked QAM256 195 55616000 Kbits/sec 307000000 Hz -6.1 dBmV 38.9 dB Hybrid
Locked QAM256 196 55616000 Kbits/sec 315000000 Hz -6.6 dBmV 38.6 dB Hybrid