DMT and missing tones

I am using DMT to try to find out what is wrong with my BB connection. I have noticed that on connection it shows several missing tones.

What impact does this have?

Depends on where they are as there are gaps where the AM radio stations exist. Other gaps could be down to local interferance.

The latest batch:
Gap1 1000kHz-1005kHz (Tone232)
Gap2 1108kHz-1113kHz (Tone257)
Gap3 1208kHz-1220kHz (Tone280-Tone282)
Gap4 1384kHz-1389kHz (Tone321)
Gap5 1393kHz-1397kHz (Tone323)
Gap6 1440kHz-1445kHz (Tone334)
Gap7 1458kHz-1462kHz (Tone338)
Gap8 1466kHz-1471kHz (Tone340)
Gap9 1475kHz-1484kHz (Tone342-Tone343)
Gap10 1492kHz-1501kHz (Tone346-Tone347)
Gap11 1522kHz-1527kHz (Tone353)
Gap12 1531kHz-1535kHz (Tone355)
Gap13 1540kHz-1544kHz (Tone357)
Gap14 1548kHz-1617kHz (Tone359-Tone374)
Gap15 1634kHz-1682kHz (Tone379-Tone389)
Gap16 1695kHz-1703kHz (Tone393-Tone394)
Gap17 1760kHz-1764kHz (Tone408)
Gap18 1945kHz-1949kHz (Tone451)
Gap19 2005kHz-2014kHz (Tone465-Tone466)
Gap20 2023kHz-2027kHz (Tone469)

In reply to a post by ukwiz:

The latest batch:
Gap1 1000kHz-1005kHz (Tone232) 999 KHz - Radio Solent
Gap2 1108kHz-1113kHz (Tone257) 1107 KHz Talk Sport Hampshire
Gap3 1208kHz-1220kHz (Tone280-Tone282) 1215KHz Absolute Radio (was Virgin)
Gap4 1384kHz-1389kHz (Tone321)
Gap5 1393kHz-1397kHz (Tone323)
Gap6 1440kHz-1445kHz (Tone334) 1445 KHz BBC Devon
Gap7 1458kHz-1462kHz (Tone338)
Gap8 1466kHz-1471kHz (Tone340)
Gap9 1475kHz-1484kHz (Tone342-Tone343)
Gap10 1492kHz-1501kHz (Tone346-Tone347)
Gap11 1522kHz-1527kHz (Tone353) 1521 KHz Gold, Reigate & Crawley
Gap12 1531kHz-1535kHz (Tone355)
Gap13 1540kHz-1544kHz (Tone357)
Gap14 1548kHz-1617kHz (Tone359-Tone374) 1557 Khz Gold, Southampton
Gap15 1634kHz-1682kHz (Tone379-Tone389) MW Band ends at 1605 KHz
Gap16 1695kHz-1703kHz (Tone393-Tone394)
Gap17 1760kHz-1764kHz (Tone408)
Gap18 1945kHz-1949kHz (Tone451)
Gap19 2005kHz-2014kHz (Tone465-Tone466)
Gap20 2023kHz-2027kHz (Tone469)

That's just the stations local to you (in bold)

Hi

quote :
What impact does this have?

The basic impact is that it will reduce you connection rate (synch rate ) unless you have Plenty Of SNR margin in other tones .

See the link below for a fuller explanation .
http://www.kitz.co.uk/adsl/adsl_technology.htm#frequ...

Regards Jeff

Edited by deleted (Wed 24-Jun-09 18:17:48)

In reply to a post by zebedeee:

In reply to a post by ukwiz:

The latest batch:
Gap1 1000kHz-1005kHz (Tone232) 999 KHz - Radio Solent
Gap2 1108kHz-1113kHz (Tone257) 1107 KHz Talk Sport Hampshire
Gap3 1208kHz-1220kHz (Tone280-Tone282) 1215KHz Absolute Radio (was Virgin)
Gap4 1384kHz-1389kHz (Tone321)
Gap5 1393kHz-1397kHz (Tone323)
Gap6 1440kHz-1445kHz (Tone334) 1445 KHz BBC Devon
Gap7 1458kHz-1462kHz (Tone338)
Gap8 1466kHz-1471kHz (Tone340)
Gap9 1475kHz-1484kHz (Tone342-Tone343)
Gap10 1492kHz-1501kHz (Tone346-Tone347)
Gap11 1522kHz-1527kHz (Tone353) 1521 KHz Gold, Reigate & Crawley
Gap12 1531kHz-1535kHz (Tone355)
Gap13 1540kHz-1544kHz (Tone357)
Gap14 1548kHz-1617kHz (Tone359-Tone374) 1557 Khz Gold, Southampton
Gap15 1634kHz-1682kHz (Tone379-Tone389) MW Band ends at 1605 KHz
Gap16 1695kHz-1703kHz (Tone393-Tone394)
Gap17 1760kHz-1764kHz (Tone408)
Gap18 1945kHz-1949kHz (Tone451)
Gap19 2005kHz-2014kHz (Tone465-Tone466)
Gap20 2023kHz-2027kHz (Tone469)

That's just the stations local to you (in bold)

Do you think this will improve when AM/FM radio is phased out over the next few years?

I certainly hope so as it would free up some tones on my DMT graph.

p.s. I'm assuming that my area won't get FTTC of course because, if it does, then I'm obviously going to ditch ADSL/2+ and go for that instead !

As I understand it, only national stations are to be phased out. Most of yours are local ones. All you can do is to keep your phone line as short as possible - you can't do anything to wiring on BT's side, but you can keep unfiltered extension wiring to a minimum.

If your router is connected to an extension socket, try fitting a filtered master socket, and connect your router directly to that, and run Cat5 ethernet to your PC.

Edited by deleted (Sun 28-Jun-09 12:08:37)

In reply to a post by zebedeee:

As I understand it, only national stations are to be phased out. Most of yours are local ones.

Thanks for confirming that.

In reply to a post by zebedeee:

All you can do is to keep your phone line as short as possible - you can't do anything to wiring on BT's side, but you can keep unfiltered extension wiring to a minimum.

If your router is connected to an extension socket, try fitting a filtered master socket, and connect your router directly to that, and run Cat5 ethernet to your PC.

I have an attenuation of around 55 dB and, as I don't have any extension wiring and already have a filtered faceplate fitted, my line won't improve unless my area gets FTTC.

As far as I understand it, certainly with MW is that any free frequencies will be sold / put up for auction anyway, so will still be in use by someone / something

FM frequencies are no where near hose in use for ADSL / ADSL2 / ADSL2+

Useful site to try and find out what frquencies correspond to what stations:

http://transmit.tv

These are just some of mine
http://transmit.tv/main.php?t=161792295
http://transmit.tv/main.php?t=30671290
http://transmit.tv/main.php?s=241471856&x=555264&y=1...
http://transmit.tv/main.php?t=577666538

Thanks for the link, it's an interesting site.

55dB attenuation, and I would expect a lot of gaps at the > 1.1MHz range as the physics means the signal is attenuated more over distance and thus the slightest noise can mean the tone is not used.

But my attenuation is 27dB.

Full stats:
Uptime: 1 day, 12:35:54
DSL Type: G.992.5 annex A
Bandwidth (Up/Down) [kbps/kbps]: 1,001 / 7,486
Data Transferred (Sent/Received) [GB/MB]: 2.32 / 358.33
Output Power (Up/Down) [dBm]: 12.0 / 18.5
Line Attenuation (Up/Down) [dB]: 15.0 / 27.5
SN Margin (Up/Down) [dB]: 16.0 / 16.5
Vendor ID (Local/Remote): TMMB / BDCM
Loss of Framing (Local/Remote): 13 / 0
Loss of Signal (Local/Remote): 4 / 0
Loss of Power (Local/Remote): 0 / 0
Loss of Link (Remote): 0
Error Seconds (Local/Remote): 9 / 0
FEC Errors (Up/Down): 49 / 35,992
CRC Errors (Up/Down): 49 / 39
HEC Errors (Up/Down): 29 / 32

Ok got confused with CurlyWhirly and you.

ADSL2+ is more prone to interference caused by extensions (used or not) in the home, hence why the I-Plate is increasing its presence (cheap version is to remove the ring wire at the master socket).

Hi,
I got looking at my missing tones, and seems a big coincidence that Radio 5, Talk Sport and Absolute Radio are spot
on the frequencies where I get 0 bits per tone.
There are some other holes I haven't yet been able to match to radio stations.
I am 32km Northeast of Brookmans Park transmitter.

I keep a summary of my bitloading log here: http://tinyurl.com/mxstld

Cheers,
Peter

In reply to a post by ukwiz:

I am using DMT to try to find out what is wrong with my BB connection. I have noticed that on connection it shows several missing tones.

What impact does this have?

It'll sound funny if it ever starts to sing

More seriously it reduces your bandwidth by between 1 and 14 bits per tone. It's likely caused by local interference. Try switching everything off and see if the tones come back. Don't resync your modem too often though if on IPStream. Another option might be to detune a radio and see if you can hear anything.

Most likely though there's nothing you can do about. Follow the advice below:

http://www.kitz.co.uk/adsl/socket.htm

..and hope for the best.

In reply to a post by CurlyWhirly:

Do you think this will improve when AM/FM radio is phased out over the next few years?

Possibly. Little else will though and it seems a high price to pay.

I think that Ofcom are backing down on that recommendation. For once they seem to have got a clue and realised how stupid it would be.