Cable Forum - Shifting modem

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- - Shifting modem (https://www.cableforum.uk/board/showthread.php?t=33691800)

misog

01-02-2013 18:46

Shifting modem

thenry

01-02-2013 19:34

Re: Shifting modem

you can do it yourself or call into VM and sort your package out. your V+ can be upgraded to a TiVo which will require a tech visit. ask the tech to move the modem while hes there. your 20meg will go to 60meg if you havent already been doubled. that will require a SuperHub. if you log into MyVirginMedia you may have an early upgrade option up top. this could be a self install, SuperHub being sent via HDNL/Yodel or a tech booking will be stated.

Sephiroth

01-02-2013 19:39

Re: Shifting modem

Quote:

Originally Posted by misog (Post 35530361)

At present I have a V+ box and telephone in the lounge and my 20M broadband modem in another room.
I want to move my PC and modem into the lounge but Virgin want £99 to move the modem.
Can I pick up a broadband connection off the connection box for the V+ or what other options have I got.

To answer your question directly, in case you want to stay with your existing package, you need a cable tv splitter in the lounge.

Incoming coax goes into the splitter, V+ and Modem come out of the splitter. Simples.

You can buy splitter on ebay.

e.g: http://www.ebay.co.uk/itm/2-Way-Sign...-/220504724690

£

misog

01-02-2013 20:28

Re: Shifting modem

Thanks Seph .
A splitter should be the simple answer BUT im not sure it will work.
As I have been a cable customer for many years my front garden is full of siamese cables which makes gardening interesting.
This means that my TV, Broadband and even telephone are on separate cables back to the cab.
If I pick up my broadband off the TV feed will it leave a noisy back end from the old unterminated broadband connection.

Sephiroth

01-02-2013 21:10

Re: Shifting modem

Simply buy a terminator or two as well. It'll work - but to be sure, just connect the modem to the V+ box and see what happens. The VM end responds to the IP header from your modem, not to the dumb tap point to which it is connected.

Let us know.

misog

02-02-2013 10:19

Re: Shifting modem

I connected the modem to the coax supplying the V+ and it worked OK thanks.
I will pick up a splitter from Maplins this afternoon.
I am concerned that the splitter may reduce the signal too much so I can return it if I have problems.
In the past the techs, rather than running a new cable for the V+, patched it onto a cable next door so its a bit flakey out there.

I have just checked the power levels and have 12.6dBmv with a SNR of 37.7 so cant see that I should have problems

Sephiroth

02-02-2013 10:54

Re: Shifting modem

The 12.6 dBmv will need taking down. The splitter will knock off about 4 dB but if you can get a 6 dB forward path attenuator as well, that would put the modem at less risk. Sometimes the SH can hack 10 or 12 dBmb; mine won't work properly if downstream power exceeds 7 dBmv.

qasdfdsaq

02-02-2013 13:19

Re: Shifting modem

Quote:

Originally Posted by misog (Post 35530512)

I am concerned that the splitter may reduce the signal too much so I can return it if I have problems.

Yes but the problem you will have is the opposite. The splitter won't reduce the signal enough. You need to reduce the signal even more.

Quote:

I have just checked the power levels and have 12.6dBmv with a SNR of 37.7 so cant see that I should have problems

The SNR is getting borderline. Splitters (and attenuators, and anything else) reduce your SNR and below 35 things can get flakey. The Superhub tends to report SNR 2-3dB higher than the old VMNG anyway, so it's "actually" already 35 by old standards.

thenry

02-02-2013 14:02

Re: Shifting modem

SNR will most probably rise once attenuation is applied.

Sephiroth

02-02-2013 14:10

Re: Shifting modem

Why?

thenry

02-02-2013 14:14

Re: Shifting modem

seen it before. SNR drops when high power levels are active. balancing of some sort.

---------- Post added at 14:14 ---------- Previous post was at 14:14 ----------

OP needs to state his upstream level

craigj2k12

02-02-2013 14:40

Re: Shifting modem

SNR (ratio of signal to noise) will change if signal or noise does

Sephiroth

02-02-2013 15:14

Re: Shifting modem

Yes - but to wjhat effect? If it's miniscule, what's the point of mentioning it?

thenry

02-02-2013 15:18

Re: Shifting modem

Quote:

Originally Posted by qasdfdsaq (Post 35530607)

misog

02-02-2013 15:33

Re: Shifting modem

Whats all this rubbish about reducing levels.
I have put the modem back onto its original connection box and have measured the levels on that cable (remember my broadband and TV are on two separate cables back to the cab) and the levels are 13.6db and a 39.1 snr. My modem has been quite happy running at that level for years.

craigj2k12

02-02-2013 15:35

Re: Shifting modem

I'm not going to go digging up old threads, but I did note the SNR change between VMNG300 and Superhub when I had both activated at once and was told by qas it was the difference in the chipset, not just the superhub reporting higher values

thenry

02-02-2013 15:36

Re: Shifting modem

its not rubbish. why have you got seperate cables from the cab. you should have 1 BB and TV cable from the cab and 1 telephone cable.

craigj2k12

02-02-2013 15:47

Re: Shifting modem

Quote:

Originally Posted by thenry (Post 35530743)

its not rubbish. why have you got seperate cables from the cab. you should have 1 BB and TV cable from the cab and 1 telephone cable.

I only had one cable, but 2 modems activated

thenry

02-02-2013 15:50

Re: Shifting modem

attitude problem.

Sephiroth

02-02-2013 16:03

Re: Shifting modem

What is the proof that the SH overestimates SNR?

---------- Post added at 15:59 ---------- Previous post was at 15:55 ----------

Quote:

Originally Posted by misog (Post 35530736)

I'm with you on this. When I moved my SH, there was no change. I've had 11 dBmv, put an attenuator on, no change; power fell, took attenuator off, no change. In all cases, no change other than the normal .05% tops variances.

---------- Post added at 16:03 ---------- Previous post was at 15:59 ----------

Quote:

Originally Posted by thenry (Post 35530743)

its not rubbish. why have you got seperate cables from the cab. you should have 1 BB and TV cable from the cab and 1 telephone cable.

Does it matter whether he has several cables from the cabinet? He can successfully move hos modem, which is all he wants to do.

thenry

02-02-2013 16:11

Re: Shifting modem

he could cause a fuss and have VM come out and sort all the cables out = no moving modem charge. tbh ive given enough to get his modem moved without charge. bye.

Sephiroth

02-02-2013 16:14

Re: Shifting modem

Why should he? It's easy enough to do as he's proved. VM have got better things to do.

Bye.

qasdfdsaq

02-02-2013 18:16

Re: Shifting modem

Quote:

Originally Posted by thenry (Post 35530637)

SNR will most probably rise once attenuation is applied.

Quite the opposite. The more rubbish you connect between the signal source and the receiver the less signal you get and the more noise you get.

---------- Post added at 18:16 ---------- Previous post was at 18:14 ----------

Back on topic. If it works, don't mess with it. If it doesn't work... that's another matter. You can sometimes maintain a working connection down to 28dB SNR - in fact 3G works down to -22dB SNR.

Course my definition of "SNR" and "works" may differ from yours.

misog

02-02-2013 19:10

Re: Shifting modem

Im a old,analogue, Cable London customer and had a lot of trouble with analogue so cables were replaced.
I think my telephone is on the original cable, my broadband on a newer one and my TV on one of next doors many cables.
As for asking Virginmedia to sort the cables out dont make me laugh.
Thanks for the help . The splitter worked and as expected reduced the levels by 4 db or so

ferretuk

02-02-2013 19:15

Re: Shifting modem

Quote:

Originally Posted by thenry (Post 35530648)

seen it before. SNR drops when high power levels are active.

Could do if the front end is overloading and clipping. Bringing the levels down would remove the resultant distortion...

Under normal circumstances, introducing a splitter should have negligible impact on the SNR - Most of the noise in the system is introduced in the street network, so although the splitter attenuates the signal, it also attenuates the noise by the same amount (in relative terms) so the ratio of signal to noise is unaffected.

The splitter will add a minute amount of noise itself of course...

craigj2k12

03-02-2013 00:40

Re: Shifting modem

Quote:

Originally Posted by Sephiroth (Post 35530769)

What is the proof that the SH overestimates SNR?

Theres no proof, as horseman suggests here, its different chips (i.e. the superhub is actually better in this respect)

Sephiroth

03-02-2013 08:26

Re: Shifting modem

QED.

qasdfdsaq

03-02-2013 16:50

Re: Shifting modem

Quote:

Originally Posted by ferretuk (Post 35530925)

Could do if the front end is overloading and clipping. Bringing the levels down would remove the resultant distortion...

True, but it really shouldn't be clipping at +12

Quote:

Under normal circumstances, introducing a splitter should have negligible impact on the SNR - Most of the noise in the system is introduced in the street network, so although the splitter attenuates the signal, it also attenuates the noise by the same amount (in relative terms) so the ratio of signal to noise is unaffected.

The splitter will add a minute amount of noise itself of course...

What do you call negligible or minute? Honest question - back on my VMNG300 each attenuator reduced SNR by 0.8-1.4dB. Two of them made it drop from a reasonable 35.5 to a not so reasonable 32.8

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