Other SOTA sites: SOTAwatch | SOTA Home | Database | Video | Photos | Shop | Mapping | FAQs | Facebook | Contact SOTA

Super Broadband VDSL


#1

Hi all UK stations,

This issue is not going to directly impact activators but it has the potential to shut down the chaser side of the hobby.

A couple of weeks ago I notice that when I transmitted on 5.260MHz a carrier immediatly apeared on the same QRG. The strength was about S1, about 20dB above noise. I completed my QSO with the carrier present, a period later I noted that the carrier had disapered. Transmit again and the carrier appeared again. A bit more investigation showed that this issue was present every 4kHz up the 60 m band and the same thing was present on 80, 40 and 30m. In each case the carriers were spaced 4kHz apart and were heard following a short transmission.

I have now exchange E mails with the RSGB EMC committee, John Rogers M0JAV@RSGB.org.uk. He assures me that these carriers are caused by Super Speed broadband modems. My transmission (less than 1 Watt is all that is needed) de-stabalises the modem and put it into a training mode. I am still assessing my situation, in my case the carriers are exactly on the frequency integers, 7.028, 7.032 10.118MHz etc making these frequencies useless for weak signal working. I understand that last year Ofcom were contacted by the RSGB and a report has been issued. Having read the report, In my opinion it is ineffective, Ofcom seem to be in deniel of the existence of a problem.

If you are aware of new carriers on your bands, with the charactaristics I have described, I recommend you advise John so he can build up a picture of the problem.

Regards
David G0EVV


#2

Sorry David to hear you have problems. You are certainly not alone with this issue it is effecting many amateurs around the country. My own solution is to move address next year to a more isolated home, so that in the future I can DX on the low HF bands should I want to.

I highlighted this problem a few months back on the reflector.The interference is different depending on your own circumstances, distance from the DLSAM VDSL cabinet, number of drop wires, etc.

It may manifest as a series of training carriers, notably on the 30m band, but I have since seen these present on 20m and now 60m as you describe.

I am located directly across the street at the edge of a village from a VDSL cabinet. The street uses overhead drop wires to feed houses their ‘fiber’ internet service.
This is a technical report submitted to the committee describing the interference at my own address. Bands effected are 40m 80m. I have used professional test and measurement equipment to quantify the noise. The report is still in a draft state, I don’t feel any more motivation to improve it, I’d rather put that effort into selling my house.

This is my report on a shared address on my google drive:

https://drive.google.com/file/d/0B9qPaAy7sooUQ0p1aGViMm0zTm8/view

Bad news, I feel the RSGB are powerless here. OpenReach are ‘willing to help’. However the problem is they’d have to replace pretty much all of the overhead wiring as it is not suitable to carry VDSL. The old wires are untwisted, and it is absolutely hopeless to expect any balance on the lines to reach better than 20dB. Add to this problem, your counting on the guy next door to terminate and distribute their line properly.

Reporting this to John however is a must. But I wouldn’t be too hopeful of a solution. Apparently, some amateurs have had success. I cannot put up any towers here, so I am not staying. My decision is motivated by a number of other factors and not just the noise.

I believe a lot of these problems in recent times are down to poor education around EMC.

Jonathan


#3

I suppose we have to live with it … this is a typical view of my 40m CW band … it is like that 24/7, whether I transmit or not :

I should be so lucky that 7.032 is not affected … but e.g. 7.033 is unusable unless the other station is S9++.
(and alas, selling my house and move is not an option for me)
73 Luc ON7DQ


#4

So its not just ‘us’ then…

Here is another guy with the same issue.

https://m0vse.uk/20-battling-with-vdsl-qrm.html

There is no doubt we will put more pressure on OpenReach. Whilst I was out on the Llyn peninsula I noticed a VDSL box out there, I consider that part of the country to have one of the lowest noise floors I’ve ever experienced.
Sadly its getting rolled out everywhere. Might even take some of our most prolific chasers out in the process.

Protests, court cases are probably on the horizon. Don’t stay silent, throw all your toys out of the pram !

Jonathan

,


#5

I get it here but it is weak and not a problem compared to the broad band noise that I suffer from. Where these signals are troublesome but not strong enough to make the AGC desense the receiver a good narrow tuneable AF notch might help, something like the old “selectoject” filter of the good old valve days!


#6

Same issue here. 40 metres is worst affected, but I see the effects on all bands up to and including 20 metres. Several favourite SOTA watering-hole frequencies are affected; 7.032, 14.060 and 14.064 in particular. The worst problems (for me) seem to come in the parts of the spectrum used to download data from the cabinet to the customer (which seems to include top band, 80 metres up to 3.75MHz, 60 metres, 40 metres, and 20 metres). My own VDSL line seems to be responsible for quite a lot of the retraining I see. I can very substantially reduce the comb on 40 metres by unplugging my modem from the phone line.

Modem unplugged and plugged back in. There’s a faint training comb still detectable in the gap, but it’s at a greatly reduced level…

The tones keep going for six or seven seconds after the modem is unplugged, then drop to a much lower level. When I plug the modem back in there’s an initial burst of tones, and then they drop off again quite soon…

After plugging it back in, the training comb is fairly short-lived. The general noise level after the comb has subsided, however, is higher than it was in the gap when the modem was un-plugged…

…until I transmit again, of course. Then back they pop.


#7

Rick, Have you reported this to John @RSGB ?


#8

This latest bit I’m about to add to the RSGB forum. The previous stufff, yes. I sent it to John back in March last year…


#9

No Brian, you are mistaken. It IS a problem. :wink:


#10

No, Andy, I am not mistaken. When I have several S-points of frying bacon noise throughout the bands that I use most, a comb of quite weak carriers is not causing me any additional problems. The filter between my ears copes adequately with the carriers, it struggles with the frying bacon!

And to think that fifty years ago I was plagued with TV time base harmonics…


#11

The fail is strong…


#12

Indeed. The failure was in your reading of my first sentence. Now give over!:tired_face:


#13

I can only assume that radio station G8ADD is sponsored by OpenReach.


#14

I cannot think of any words or expressions to describe his lack of clarity in his thoughts that are suitable for a family website such as this.


#15

OK, good.

The more information John has the better.

Anyone thinks this is a minor ‘problem’. Tune your car radio to ~ 600kHz AM and drive around in a nearby village / town. You’ll soon appreciate why noise levels have gone up when you approach a telegraph pole !


#16

pray tell me how do you do that with a DAB radio as fitted in “modern” cars?
Eh?
73
Ken


#17

Well if you’ve got DAB and/or an ‘analogue’ tuner fitted you can do it, can’t you ?

I don’t think its that uncommon. I have a 2012 plate, has an AM radio…

Cannot vouch for other cars.

Jonathan


#18

An amazing attack of word-blindness or an incapability to comprehend the significance of the word “here”. Now for heaven’s sake, stop acting dumb, you are distracting from the topic!


#19

[quote=“G0EVV, post:1, topic:15688”]I am still assessing my situation, in my case the carriers are exactly on the frequency integers, 7.028, 7.032 10.118MHz etc making these frequencies useless for weak signal working.[/quote]Not just for weak signals, either. Good examples (for me) this morning. First:

Fri 08:20	YU1RK/P on YU/IS-081	14.0656 cw
*[RBNHole] at SK3GW 24 WPM 27 dB SNR (Posted by RBNHOLE)

A nice strong signal well clear of any of the *DSL training tones, so an easy contact.

Then:

Fri 09:24	HB9BQU/P on HB/VS-026	7.032 cw
*[RBNHole] at GW8IZR 23 WPM 5 dB SNR (Posted by RBNHOLE)

Not quite as strong a signal, but would have been fairly easily workable except for the *DSL carrier about 40 to 50 Hz below. Even using the narrowest available filtering I couldn’t reliably split the activator’s signal from the training carrier well enough to make it workable. If the activator had been even 50 Hz higher it would have been a fairly easy contact. As it was, no contact.


#20

Hi All,

Thank you all for your contributions to this subject, I have learnt a lot in a week.

Clearly VDSL is a significant threat to SOTA, both in the UK and Europe. In conjunction with a local amateur who is the owner of a quality spectrum analyser, as requested by Roger, I am going to see if I can quantify the issues at my QTH were the telephone lines enter the property underground. I am sure that this problem is not going to go away, or to be soon resolved by the purveyors of super speed modems.

From the SOTA perspective what we need is to develop a work around solution:

I am not sure how this threat affects SSB but for CW I suggest, we should avoid centering our carrier on any integer.frequency so we should not use 7.028 or 7.032 ( I am unsure if the modems all have a same frequency comb with a spacing of 4kHz). The one observation is that that the modem signals are very frequency accurate, being within a few Hertz of the integer frequencies.

I suggest we harness this frequency accuracy to our benefit so activators should use:

7.0324, 7.0326 etc
10.1184, 10.1186 etc
14.0624, 14.626 etc
Lets play the game, keep away from kHz integers. not difficult really!

Please keep your suggestions coming.

Regards
David G0EVV