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Hello Everyone.
I think you will find that with your line length
from the serving exchange (7km)? the S/N ratio will be poor, a
minimum of 10dB is required, my copper connection is about 2.7km which is
considered to be approaching the limit, although the tests at the customer NTE
showed that 3Mbt/s.should have been possible. At these line lengths
any rf will swamp the DSL signal. I have discussed this problem at length
several time with the people I worked with at Adastral Park ( commonly known as
BT Labs), both DSL and EMC, the problem is compounded if a) you have a long
length of overhead drop wire, b) the number and configuration of
any internal extensions, and c) the position of the router with respect to the
incomming NTE (master socket). If the dropwire is long, the induced common mode
interference will be transformed into differential mode before it reaches the
router, any internal extension wiring will increase attenuation, especially if
it is a 'star configuration.
The router should be as close as possible to the
incoming NTE. A spectral analysis of my line revealed that there were no DSL
carriers above 500kHz, hence not being able to use 500kHz, if the router
shuts down because a corrupted incoming signal, it will start a 're-training'
sequence with the DSLAM in the serving exchange, however if either the line or
the router is changed, the exchange equipment will then go though a process of
determining the best possible data speed of the new configuration, thia can take
up to ten days, if during this time any of the speedtest sites are used
different data rates will be loged.
I changed my 1st generation BT Homehub router
for an older BT Voyager 2500, which improved the situation with the
HF bands but not at 500kHz, even with high value common mode chokes on
everything in sight. The problem was finally solved by changing over to BT
Infinity Fibre To The Cabinet (FTTC) with copper line length of 400m giving data
speeds of 14Mbt/s.
I hope some of this is both of use and interest you
all.
73
Ken
M0KHW
----- Original Message -----
Sent: Friday, November 26, 2010 10:08
AM
Subject: Re: LF: Any ADSL2 BBand router /
RF proof ?
|
Hi Again Graham and LF
Hmmmmm OK looks like you are in better shape than me. A local
station who has difficulty with his ADSL has put Ferrite clamp on
filters on all leads in and out of the Modem including the power supply
lead. He claims (and I have no reason to doubt him) that this has solved
his problems. The modem is the new BT Black Box one. I have one of those
although much more reliable and faster it still suffers from my
description below. The issue I have appears not to be Modem related but
exchange based.
I talk to Larry regularly on 4m so next time, if I remember, I will
get the details of his solution Viz ferrite type and where on the lines
he is fitting them and forward it to you. It may help.
As before good luck with your efforts; what ever success you get
please publish it. Ken M0 KHW Luton has an ADSL problem
too so several people would be interested I am sure. 73 es GL
petefmt I support www.NotSpotTelecom.Com your community Telco /
ISP. --- On Fri, 26/11/10, Graham
<[email protected]> wrote:
From:
Graham <[email protected]>
Subject: Re: LF: Any ADSL2
BBand router / RF proof ?
To: [email protected]
Date:
Friday, 26 November, 2010, 0:49
Ok Pete
This is the new router , as
its in the same place as the old one , with (now)
the same filters , the PC is linked with
a short network cable , the rest of the pc's
are linked by radio. its the adsl like thats
failing
The edimax router was
quite robust , never had a drop out on HF and only
over 200 watts , feed , on 500 would stop
the link , this one fails with 25
watts on 160 .. the router is off
most of the day and night , only
on with the pc , the new router is
faster , from 6 (old) meg to 9 med down
and 500k (old) to 890 k upload , but if
it keeps dropping out with no cure
then its not much use for my usage
G,
Sent: Friday, November 26, 2010 12:26 AM
Subject: Re: LF: Any ADSL2 BBand router / RF proof
?
|
Hi Graham
Are you sure the problem is the router?
136, 500, 160 and to some extent 80m here are
kill the ADSL. Even at very low powers. If
your ADSL is cut during your transmissions only and
resumes at the original speed directly afterwards it may
well be the router being temporarily being knocked out. If
however you line stays down for a period of time say
several hours then it is not the router. What you are
doing is putting noise (owing to RF) onto your line which
is being picked up at the exchange DSLAM. The exchange
equipment (DSLAM) serving your line will reduce data speed
to ensure that a connection of sorts is maintained. This
speed can go down to below 80kb/s from which it will not
recover without technical intervention by BT Open Reach.
If it goes down to about 300/500kb/s it may well recover
it's original speed over a period of time BT quote 72
hours yes 72 hours (I think this time period is not a
technical issue but one to stall the punters off). On a
good day the recovery period can be speeded up by turning
the router off and disconnecting every thing from the line
and waiting. This makes a quiet line for the automatic
recovery to work.... on a good day!!! If you don't have
enough life left to wait for BT to physically do some
thing then the best thing is to write to BT HQ in London
to the their CEO (his name and location can be found with
a bit of research) and tell him what you think of his
outfit. I know from experience he does not like receiving
this kind of letter. You may have your ISP as Joe Blogs
Internet Provider dot Com but in reality it is all
provided by BT they own the final mile and the exchange
...... legal niceties to one side it is a fact.
If you get a good Broad Band data rate of
say 4/8mb/s your transmissions on LF/MF will only
slightly degrade your ADSL but if like me on the end of
7.5km of copper its only 1/1.5mb/s on a very good day, RF
will wipe out your ADSL for a week or more.
So without a lot of letter writing to BT and
angry phone calls your ASDL will not return to original
speed..
To maintain a usable data rate on Broad Band here I
can not use 136 or 500kc/s above a few Milli Watts at TX
output about 1 Watt on 160m 80 about 50Watts and on
60m and above 100Watts (possibly more but not tested
yet). Also the longer you stay on the worst the speed
degrades.My guess is with ADSL2 having a much wider
bandwidth the problem for Amateurs will extend further up
the spectrum than shown above.
Hope you are not in my situation....... Oh and don't
believe all this Fibre stuff. Open Reach have told me
that one reason why Fibre is not being rolled out like the
Virgin setup is that there are only a few BT people
capable of working with Fibre. This is the reason
why BT is Wedded to copper wire. So we locally have
Internet breakdowns owing to Junkies and the like ripping
the Copper cables out of BT ducting to pay for
drugs... Bedfordshire has had Internet disconnections for
days owing to this phenomenon. So along with cable theft
and the lack of trained staff a proper interference
free Broad Band coverage using fibre in this country
is looking particularly bleak.
Good luck! 73 es GL
petefmt I support www.NotSpotTelecom.Com your
community Telco / ISP. --- On Thu, 25/11/10,
Graham <[email protected]>
wrote:
From:
Graham <[email protected]>
Subject: LF:
Any ADSL2 BBand router / RF proof ?
To:
[email protected]
Date: Thursday, 25
November, 2010, 22:06
Any ADSL2 BBand
router / RF proof ?
Just upgraded to
ADSL2 with a orange
net-gear router/wifi router,
now 15 watts on 160
kills the connection
router is in the same
location as the old edimax , which
kept running with 200 watts on 500
K and 400 on Hf
? any RF
proof ADSL2 on the
market >
Tnx -
G..
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