100M HDU installed, problems since.

InfiniteBiscuit · 03-12-2012, 23:13

Hello forum.

Last week I had an HDU I think it's called, installed. Powered three way splitter. As I was having trouble getting on demand/interactive in the bedroom. Mr Engineer came out, stated that the power levels were far too high in this flat, and that I would need an HDU to resolve the issue.

So he installed one. Then when he couldn't get the box working anyways, he decided to give me a new box. And voila, it works!

However, ever since my internet has been reduced to garbage. Engineer told me I'd need the HDU plugged in all the time, as I wouldn't get internet or the TV service in the bedroom otherwise.

But my internet is now suffering awful latency times, a lot of jitter, and occasional packet loss.

As some who quite enjoys shooting people on Call of Duty, this is becoming irritating. What can be done?

jb66 · 04-12-2012, 07:42

whats your signal levels?

General Maximus · 04-12-2012, 08:51

it is more likely that you didn't need the HDU ti start off with and the box was faulty and installing the HDU has nnow screwed up yur power levels

Sephiroth · 04-12-2012, 10:45

As mon General says, if power is too high (downstream, I assume), an HDU is not needed. An HDU would boost a hopefully clean incoming signal and distribute it to multiple points.

The use of the word "box" in the foregoing posts has rather confused me. Presumably it means the HDU and not the modem.

The usual supplied device by VM (AFAIK) can be googled as TRATEC 85-FDU-APPNOTE.

InfiniteBiscuit · 04-12-2012, 11:15

Thanks for the replies, people.

I'll post some signal levels when home, and I'll likely put the old non powered splitter on, as the engineer left that.

When referring to the 'box', I meant the V+ box. I should have specified.

Basically, the engineer said the HDU would fix the issue, and when it didn't, he replaced the V+ anyways.

Sephiroth · 04-12-2012, 11:33

Here's a sort of look ahead on this.

1/
If your downstream power levels on your modem are > -3 dBmv, your signal to the V+ box won't need boosting.

2/
If your modem downstream SNR is < 34.5dB, then you're potentially (but nt necessarily) at the edge of a trouble zone that the HDU cannot fix.

3/
If your upstream power (before the HDU was installed) is high - say above 50 dBmv, then the HDU isn't going to help that either, although it might be a necessary level due to your distance from the street cabinet. If your upstream power is 55 dBmv (you need to refresh the power screen a few times to see if it is moving in that direction), then there is an upstream problem that cannot be fixed by the HDU.

The typical application for an HDU is where you live at the end of the cable run from the street cabinet and you have a number of devices split off at the external wall box. The aim of the HDU is to ensure that there is no further powe level drop due to the length of cable around your house to the several devices.

The V+ box will tell you in the Settings menu what the power levels & SNR are. Would be useful to compare against the modem.

HTH

InfiniteBiscuit · 04-12-2012, 13:19

That's all good to know, thanks. I'll have a look either tonight or tomorrow and update the post.

The engineer seemed to think that the HDU was the greatest piece of kit in the world. "This'll solve all your internet problems." I didn't have any problems until it was installed. Latency was always low, rarely dropped out, and I'm lucky enough to have always have a consistent speed at the 100Mbps mark.

Stephen · 04-12-2012, 14:06

I had a HDU installed when I moved house and nothing ever worked. After a fault tech came out he removed it for a non powered splitter as he said my power levels were spot on but spiking a little high and the HDU couldn't cope.

Tech that originally installed the HDU tried to tell me they have to install them for every install now! nonsense I thought.

Just glad it was removed.

jb66 · 04-12-2012, 15:00

When you have a long cable run RG11 is more effective than an HDU as the high frequency signals will be very low.

HDUs are mostly used in sid architecture where there are a set of taps every 20m. If your close to the amp there will be a 26db attenuated tap to lower the downstream, unfortunatly the upstream will also be attenuated by 26db so will be high. Its common for the upstream to be 47db from the pit in those situations. Add a 3 way splitter and a few connectors and the upstream rises above 55db.

Sephiroth · 04-12-2012, 15:31

Quote:

Originally Posted by jb66

When you have a long cable run RG11 is more effective than an HDU as the high frequency signals will be very low.

HDUs are mostly used in sid architecture where there are a set of taps every 20m. If your close to the amp there will be a 26db attenuated tap to lower the downstream, unfortunatly the upstream will also be attenuated by 26db so will be high. Its common for the upstream to be 47db from the pit in those situations. Add a 3 way splitter and a few connectors and the upstream rises above 55db.

Just to expand on JB's explanation. If you are close to the amp, the upstream power required to be drawn from your modem will be lower than if you are further away. That's why the 0 dBmv/40 dBmv downstream/upstream sweet point rule of thumb is used. I'm close-ish to the amp and in the days before I had 4 taps at the hope, my modem only needed 29 dBmv to get back to the first active node (optical). Another rule of thumb is that each active node needs to see at least 15 dBmv input power - there are settings to control this and the rule is not fixed because of infrastructure differences from area to area.

Now mine is c. 40 dBmv. But in SID areas, it's as JB explains because of the attenuation at each pit.

But you can do the maths once you've worked out the upstream attenuation to the amp, plus the tap point attenuation etc. So JB is essentially correct.
.

RB2004 · 05-12-2012, 00:34

Quote:

Originally Posted by jb66

When you have a long cable run RG11 is more effective than an HDU as the high frequency signals will be very low.

HDUs are mostly used in sid architecture where there are a set of taps every 20m. If your close to the amp there will be a 26db attenuated tap to lower the downstream, unfortunatly the upstream will also be attenuated by 26db so will be high. Its common for the upstream to be 47db from the pit in those situations. Add a 3 way splitter and a few connectors and the upstream rises above 55db.

That was the setup here, pit very 20 metres or so, then I had 5 devices in the house.

So my signal levels were borderline -5 to -7 dbmv

With slightly high upstream.

But in my case I had a few engineers out and none would fit a HDU.

In the end had to fit one myself and now signal levels are spot on

and no problems since!