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Old February 21st 18, 09:15 AM posted to uk.telecom.broadband
Martin Brown[_2_]
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Posts: 99
Default BT HH4 speed issue

On 20/02/2018 17:24, Woody wrote:
A friend who is a farmer also runs a small caravan site and has provided
free wi-fi for his guests. He is at the end of almost 3000m of (mainly)
overhead line and so the download speed is slow.

My exchage only line is slightly longer than that and about 20% above
ground. I am on the wrong side of the beck and the underground line is
in water. I get 5.5Mbps sync provided there are no gremlins or spiders
in the works. (many people do not get 2Mbps off the same exchange)

When we arrived on site last month it was doing almost 1.6Mb. We then had
two nights of heavy rain and frighteningly high winds. When I checked again
the download was only 650K but the upload was unchanged at about 760K. The
farm is in East Somerset: Speedtest using Vodafone servers at Newbury gives
about 19mS ping.

That is a bit of an odd combination. If the SNR is so bad as to only
support a 1.6Mb sync rate why is the upload speed not pegged at 448k?
And more than that why is it still on FASTPATH with sub 20ms pings?

It would almost certainly benefit from interleaving error correction on
and the upload speed dropping. Resynching at a time of day where radio
interference is strongest will force a slightly more robust connection.
My ping is about 40ms due to interleaving being on.

It would be worth trying the bellwire hack on the slower lines to see if
it will help improve rejection of RF noise. It gained me +50%. YMMV

When we revisited this month the speed was unchanged - 650K and 760K. Today
I power cycled the HH4 and within 10 minutes it was doing 1.53Mb: now, some
6 hours later it is doing just over 1.8Mb with upload still at 760K.

Sounds a bit like spiral of death problems while you are not there.
Every time the line drops for SNR issues it will retrain to a probably
slower speed. Running a better router that supports routerstats might
shed some light on what is going on. Likewise for error stats.

FWIW I get an insane number of Interleave FEC corrections on my uplink
(but then I do upload a fair amount of stuff).

Putting the thing on a timer to cycle the power at 1am might improve
things from the perspective of daytime users.

Two questions:

Should the HH4 have retrained to the higher speed without need for power
cycle intervention, should I try to get himself to use a better router, or
is this a BTOR issue? All lines incidentally are through BT Business.

Yes but rather slowly for modest speed improvements (and any glitches
will cause an immediate loss of sync speed). What features is the
exchange capable of - I'm guessing it is ADSL Max enabled?

The overhead carries four pairs all of which are active and carry their own
broadband. BT dslchecker indicates two lines (those used for the campers
the domestic B/B) should be able to do 1-3Mb, the third line (used for the
farm business) should be able to do 2.5-3.5Mb, and the fourth line (used by
his son's business) should be able to handle 2-6Mb - and indeed this seems
to be the case, today the latter line was doing 5.86Mb. It baffles me that
four lines all running the same route and in the same cable (there are no
streetcabs on this exchange) can have such speed variation. They are all

It may well depend on the routes they take and the state of connections.
It puzzles me a bit too that you could have three speeds quite so
different at the same geographic location.

direct exchange lines (fibre is not available on this exchange and there is
no LLU) and have a single U/G and O/H cable feed. About six houses in a
hamlet that also use the same feed (split at a* pole-top DP) I am told also
suffer from slow speeds. For the record I have done quiet line tests on the
campers line and on the high-speed (!) line: the campers line is (a bit)
lower audio level than the other and has noticeably more hiss on it but
neither has any crackling and both ring without problem.

Anyone any suggestions on either or both questions?

Low signal and more hiss doesn't sound ideal. Can you measure the
properties of each line with a modem capable of real diagnostics?

Martin Brown