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Author Topic: Keeping Medium Wave transmissions out of VDSL ?  (Read 1222 times)

adsb

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Keeping Medium Wave transmissions out of VDSL ?
« on: July 06, 2017, 04:53:18 PM »

My VDSL has always been disappointingly slow, and having looked at the QLN figures during the day I can see that strong Medium Wave signals are wiping out quite a chunk of the spectrum.

http://www.adsb.co.uk/blog/medium_wave_kills_vdsl.html

I'm about 10km from Brookmans Park, and about 8km from Saffron Green.  If my experience is typical, how on earth do users closer to these transmitters manage with VDSL ?  And if my experience isn't typical, is there anything I can do to improve matters ?  The strongest signals are -85 (don't know the units, dBm perhaps ?).
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ejs

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Re: Keeping Medium Wave transmissions out of VDSL ?
« Reply #1 on: July 06, 2017, 05:18:39 PM »

So what are your actual and estimated speeds?

You've already highlighted things like the non-twisted pair dropwire which ought to be replaced.

The only other aspect is that these frequencies are used by both VDSL2 and ADSL2+, and so the VDSL2 signals tend to operate at reduced power (adjusted so that the VDSL2 signals from the cabinet are the same strength as ADSL2+ signals from the exchange when they reach the cabinet, so it depends on the distance between exchange and cabinet). So this part of the spectrum often has greatly reduced bitloading on VDSL2 anyway.
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adsb

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Re: Keeping Medium Wave transmissions out of VDSL ?
« Reply #2 on: July 06, 2017, 05:44:14 PM »

So what are your actual and estimated speeds?
The estimated speed for a clean line is 27.4 - 36.6 Mbps with a handback threshold of 25 Mbps.
The best VDSL sync speed I've ever achieved is 22.4 Mbps.
The estimated speed for an impacted line is 15 - 30 Mbps with a handback threshold of 11.4 Mbps.  The BT Wholesale speed estimator says there's no bridge tap, so I guess a have a "copper line condition" - and that's not the same thing as a fault.

You've already highlighted things like the non-twisted pair dropwire which ought to be replaced.
Indeed, just that Openreach won't replace it.  They install lines, and fix faults.  But old and nasty wiring doesn't count as a fault.

The only other aspect is that these frequencies are used by both VDSL2 and ADSL2+, and so the VDSL2 signals tend to operate at reduced power (adjusted so that the VDSL2 signals from the cabinet are the same strength as ADSL2+ signals from the exchange when they reach the cabinet, so it depends on the distance between exchange and cabinet). So this part of the spectrum often has greatly reduced bitloading on VDSL2 anyway.
Ah, OK.  The cabinet is ~2.2 km from the exchange, so the VDSL signals might be down quite a way.
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j0hn

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Re: Keeping Medium Wave transmissions out of VDSL ?
« Reply #3 on: July 06, 2017, 05:46:37 PM »

Quote
Indeed, just that Openreach won't replace it.  They install lines, and fix faults.  But old and nasty wiring doesn't count as a fault.
It doesn't meet their own standard if it isn't twisted pair.
Have you tried the CEO, if the average engineer wasn't willing to replace it?
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Talktalk FTTP 550/75 - Speedtest - BQM

banger

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Re: Keeping Medium Wave transmissions out of VDSL ?
« Reply #4 on: July 06, 2017, 07:10:31 PM »

I had mine replaced. It was Dropwire 6 underground and dug 30 metres of my drive up as the wire was partially under flagstones not in the duct so couldn't be pulled through. It was replaced with an underground twisted pair and gave me an extra 13 meg sync. If as suggested an engineer won't ask triage get on to Openreach CEO.
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Tim
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Asus RT-AC68U and ZyXEL VMG1312-B10A Bridge on 80 Meg TTB Fibre

https://www.thinkbroadband.com/speedtest/1502566996147131655