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Sephiroth
Alessandro Volta
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Message 21 of 26
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Re: New Installation, Suboptimal Speeds

The technicians get some training (I have a copy of the video that forms part of that training and that deals with attenuators). But they don't always really understand how the system works. So, when they are sent out to you, with the mission that upstream power levels are too low, they slap an attenuator on which increases the push from the hub and then promptly attenuates back to what it was before.

The advice you have been given by others in this thread is that 30dBmv on the upstream is below the recommended threshold. Indeed, that is what the technicians are told. However, in my sticky thread giving reasoned advice, I say that anything lower than 50dBmv is fine and I provide the technical explanation to back that up ( https://community.virginmedia.com/t5/Speed/POWER-LEVELS-amp-SNR-A-TECHNICAL-PRIMER-updated-October-2... ).

In my estimation, whatever has happened now, was going to happen without the technician's visit. Whether or not that has improved your downstream speed may still be an outstanding matter.

Seph - ( DEFROCKED - My advice is at your risk)

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Sephiroth
Alessandro Volta
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Message 22 of 26
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Re: New Installation, Suboptimal Speeds


@glenmore3685 wrote:

Upon further reading, could my original upstream level have been fine? I read that if you're close to the cabinet the hub doesn't need to kick out a lot of power in that situation? [SEPH]: Correct for coax cable.  Was that in my sticky thread and do you believe me?

I read that the Hub is told the power level to apply and told to increase it if required, does that mean the hub was told to kick out the upstream level it was and that was fine?  [SEPH]: More or less.  The hub increases the power level (I think from 15) until the VM end says, I read you error free.

SO CONFUSED!!! Smiley Very Happy

BTW I have a fibre to the property installation if that makes any difference to anything.  [SEPH]: Makes a huge difference.  The technician's advice from 2016 (which may have been updated but I'm not privy to that) was based on coax cable to the property.  With fibre to the property, there is negligible power loss .

Your Hub 3 is coax driven - so the attenuator reduces power to the media convertor that VM have installed in/on your poperty.  Fibre thereafter with negligible loss to the first active node.

 


 

Seph - ( DEFROCKED - My advice is at your risk)

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glenmore3685
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Message 23 of 26
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Re: New Installation, Suboptimal Speeds

Sorry if any of my responses suggest I don't believe you, that is certainly not the case!

The penny has dropped, I get that the hub is pushing out an extra 6db but this is being removed by the attenuator that's plugged into the back of it. In effect all the attenuator has done is lowered the downstream levels that didn't require lowering. 

Incidentally I was running some tests before the engineer showed up and the speeds were actually as expected for 350, the attenuator didn't change them. When he showed up I mentioned the speeds appeared OK but the upstream was out of spec so he then fitted it. He did mention he was still an apprentice! 

I think I'm going to remove the attenuator....

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Sephiroth
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Message 24 of 26
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Re: New Installation, Suboptimal Speeds


@glenmore3685 wrote:

Sorry if any of my responses suggest I don't believe you, that is certainly not the case! [SEPH]: Never entered my head!

The penny has dropped, I get that the hub is pushing out an extra 6db but this is being removed by the attenuator that's plugged into the back of it. In effect all the attenuator has done is lowered the downstream levels that didn't require lowering. [SEPH]: Correct.

Incidentally I was running some tests before the engineer showed up and the speeds were actually as expected for 350, the attenuator didn't change them. When he showed up I mentioned the speeds appeared OK but the upstream was out of spec so he then fitted it. He did mention he was still an apprentice!  [SEPH]: He prolly won't know more when he's not an apprentice unless he reads stuff like the sticky thread!

I think I'm going to remove the attenuator.... [SEPH]: I would. Do please report back, though.

 


 

Seph - ( DEFROCKED - My advice is at your risk)

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glenmore3685
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Message 25 of 26
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Re: New Installation, Suboptimal Speeds

OK attenuator removed, stats back to where they were before. Post removal speed test @ Ethernet connected machine stable and where it should be. I seem to have an issue with a laptop that doesn't appear able to get higher than 280 mbps but that's my issue rather than Virgin's.

I'll monitor for a few days but all appears well at the moment.

It's clear that the hub is able to increase the upstream power if required which leads me to the question that if it was requested to (or needed to) increase the upstream I assume it could? I therefore assume that the system is happy with the 30.3 upstream power level and the fact its not within spec is not a major issue?

 

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Sephiroth
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Message 26 of 26
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Re: New Installation, Suboptimal Speeds

Yep - your queries are resolved.

Seph - ( DEFROCKED - My advice is at your risk)