Continual degradation of speed.

[Vince2]

Hi all, I have a long standing (years) issue with a degradation of speed over a number of months. I have had so many engineers' visits that I now know them all personally! I am a licensed amateur radio operator with an FTTC connection to a cabinet just under a mile away. There is, alas, overhead copper wire for the final leg to the premises. I have, for a long time suspected that my HF radio activities are the cause of this issue which sees my speed (after an engineer's DLM reset) start at 40mbps and, over a period of months degrade past the 19mbps "stay fast" threshold and continue downwards to the point where it is unusable. When I have mentioned my suspicions to the visiting engineers they have largely been sceptical, mainly I suspect they don't come across this issue very often. All they have done is say they can't find any problem, do a DLM reset and start the merry go round off again. The last engineer to visit was more receptive and we proved beyond doubt that this was the problem with him monitoring the line while I transmitted a low-power steady carrier. We have the latest faceplate and there are no extraneous house wiring left over from previous corded extension phones. From my own tests any transmissions on the low bands i.e. 3.5MHz, 5MHz, 7MHz and 10MHz case an almost instantaneous reduction in the Noise Margin from normality at 7db to 5db or less. Thus over time DLM considers the line to be unstable and reduced speed accordingly. Any transmissions in the bands at 14MHz and above don't affect the Noise Margin, presumably because they are notched. So, every 3 months or so I call BT , they send out an OR engineer who scratches his head, does a few tests and resets the DLM. Three months or so later the whole process starts again. This is getting very tedious and I need a permanent solution. I want to enjoy my hobby of over 40 years without hassle - can anyone suggest what my next steps should be? Vince

[licquorice]

I'm afraid there is very little, if anything, you can do to prevent the interference. VDSL uses the frequency range of 25Khz to 17Mhz.

Have the RSGB got any ideas, you are more likely to get a solution there.

A drastic solution is to turn off your hub whilst active with the radio ensuring at least an hour between turning off and back on again to prevent DLM considering it a fault, but that is not really practical.

FTTP if and when it becomes available to you is probably the only answer.

[Keith_Beddoe]

4G mobile broadband might be another option, if you have a good 4G mobile signal. Or if you are prepared to get a lower speed, then an ADSL connection would be another option, unless of course you use 160M.

[Ribblelancs]

Have you asked RSGB?

It's a difficult subject.  Have heard of a case where neighbours were complaining, (without substantial proof). OFCOM claim the there's no problem with Amateur Radio.

RSGB may give advice on the Antenna type and orientation. 

[Vince2]

Hi all,

Thanks to everyone for taking the time and the trouble to respond.  My apologies for the lack of line feeds in the original post.  They were there when I hit send but the forum software seems to have stripped them out.

I didn't expect there would be much I could do, but it was worth a try.

I've discussed this with the RSGB EMC committee rep and he says that there's little that can be done as well.

Speed is not important to me, I could live with, say 15mbps or even less.  In this day and age how do I go about asking for an ADSL line?

Interestingly enough, my immediate neighbours either side are not with BT and they don't have any speed or reliability isuues at all.  I'm not sure how that can be unless there are other ISPs without DLM or with a different sort of "line conditioning"  system.

I've always asked BT to intervene once the speed hits 15 so I've never seen just how far DLM would reduce it.  Is there a limit to how low it will go?

Many thanks again for yuor help and suggestions...

Vince

[licquorice]

Different ISPs use different DLM algorithms, there are basically 3 settings Speed, Standard and Stable. Speed prioritises speed of stability and Stable prioritises stability over speed. It is believed BT use the speed profile but nothing with DLM is very transparent. Have a look at https://kitz.co.uk/adsl/DLM.htm for an explanation of DLM.

[Vince2]

Thank you - I'll do that.

I've been looking at the possibility of changing to ADSL but

1) I'm too far from the exchange to get anything much more than about 5mbps

2) Just got off the phone with BT and they will simply not entertain a VDSL to ADSL swap. I need to see my contract out and then see what happens.

Thanks