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mickbirch2000 Posts: 745 Forum Member ✭✭
28/02/10 - 10:03 in Broadband Internet #1
I have recently become aware of the effect of the old AM transmitters have on broadband. In Bournemouth we have 5 medium wave transmissions from Fern Barrow.
1/ 1.3 Mhz 850w Radio Solent
2/ 1.19 Mhz 250w Virgin
3/ 1.05 Mhz 1Kw Talksport
4/ 0.9 Mhz 250w Radio 5 live
5/ 0.8 Mhz 270w Classic Gold
They are all fairly low power but still powerful enough to affect my broadband I live approx 3Km from the transmitter site.
Using the DMT tool which interrogates my voyager 2110 & produces graphs of s/n etc there are 3 gaps in the usable DSL channels which correspond exactly with the frequencies of Talksport, Radio 5 live & Classic Gold.
My broadband is ADSL2 mode currently, it was ADSL2+ mode but noise problems in the evenings have made it revert to ADSL2.
I thought AM medium wave radio transmissions were being phased out with the advent of DAB etc.
I personally now use a Roberts stream 202 radio & can stream litterally thousands of radio stations including all the local ones via the internet which works very well for me.
There are now so many platforms for radio reception isnt it about time there was some rationalisation.
Mick
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tellytart1 Posts: 3,684
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Make sure you have the bell wire (pin 3) disconnected from your master socket to the extensions, as this is a single wire and will act like an antenna picking these transmissions up and cauing extra inteference on your phone line.
The phone line itself is two wires operating in balanced mode, so should be less suceptible to the AM inteference.
As a result of removing the bell wire, you may find your sync speeds go up.
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mickbirch2000 Posts: 745
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28/02/10 - 11:10 #3
tellytart1 wrote: »
Make sure you have the bell wire (pin 3) disconnected from your master socket to the extensions, as this is a single wire and will act like an antenna picking these transmissions up and cauing extra inteference on your phone line.
The phone line itself is two wires operating in balanced mode, so should be less suceptible to the AM inteference.
As a result of removing the bell wire, you may find your sync speeds go up.
Yes I did that about 3years ago to get the DSLmax up to 8Mb to stabilise, before I was getting approx 10 re-syncs every evening, the BT helpdesk were absolutely of no use in those days, are they any better now?
That one thing made a huge difference & then updating the voyager 2110 firmware more recently also improved things.
Unfortunately the cable to our flats is above ground to cross the road & then dives underground again into the flats. That small section on poles & then the internal wiring is enough to act as an aerial despite being balanced pairs.
I might have a look at the internal wiring to make sure proper twisted pair cables were used.
Mick -
Earake Posts: 1,808
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28/02/10 - 11:15 #4
Are you using this ?
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mickbirch2000 Posts: 745
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28/02/10 - 11:27 #5
Earake wrote: »
Are you using this ?
Yes thats the site that I found all the info, didnt realise we had so many medium wave transmissions locally.
Mick -
WellHiddenMark Posts: 1,797
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28/02/10 - 12:18 #6
It was my understanding that these frequencies are actually notched out at the MSAN in the exchange rather than by the modem at the customer premises.
This is why the theoretical maximum of 24 Mbps is just that, a theoretical.
Certainly the whole of Manchester is affected by some very strong AM radio signals. Once AM radio is gone, everyone's ADSL speed will go up by several hundred kbps.
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The Sack Posts: 10,805
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28/02/10 - 17:30 #7
The effects will become less in the summer when the sun is up longer to supress the MW signal but TBH if you are getting resyncs that would suggest your router isnt hanging on to the noise margin rather than it being as simple as the local transmitters knocking it out. DMT shows some massive gaps all over the shop but my DSL is very stable.
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mickbirch2000 Posts: 745
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01/03/10 - 09:44 #8
Re-booted the voyager this morning & its now gone back to ADSL2+ mode with 6.4db down & 6.6db up noise margins.
There are 5 holes or channels missing in the band on DMT, how much affect that is having I dont know but my sync speeds are 11.5Mb/s down & 1.2Mb/s up which is more a factor of line length I think as its 38db line loss.
I will see if the router manages to hold onto this mode/speed over the next few days, still on default 6db SNR, havent tried adjusting it with dmt but I may do just to see whats possible.
Mick -
[Deleted User] Posts: 947
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02/03/10 - 12:53 #9
you will always see gaps in the tones where there is a local AM transmitter, and as a result will lose a small amount of bandwidth.
unfortunately there is pretty much nothing that can be done until AM radio is phased out.
It will only play a major effect on your line if there is a fault with your pair, such as low insulation or it is not balanced(as previously suggested). when this is the case the AM radio sometimes becomes apparent on the PSTN frequencies and can be heard with a TELE290 (http://www.hbl.co.uk/downloads/productsheets/telecom/test_telephone_290_en.pdf) set on monitor. fitting an RF3 filter to the line can help(a very very little), but that will only protect from transmitters spilling into the broadband spectrum.The main reason that AM/MW interference can affect b/b is your CB radios where the equipment is not properly shielded/earthed and this can be a nuisance. REIN also appears like an AM transmitter and will usually cause tones to be missing around the 600Khz (tune your car radio and have a drive round, the world is a noisy place) region, however depending on the severity and proximity will determine if that is what is affecting your line.
The MSANS do transmit at those frequencys, as when i have done frequency spectrum analysis on a line i can see the spikes of the local AM transmitters and the corresponding gaps in the tones graphs, on one line, then much reduced spikes and a few tones on another line out of the same exchange.:)
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