21-08-2018, 01:12 PM
* I'll expand on how I more than tripled my sync speed. I've made this a separate post to hopefully make it clear to Old Sparky that this is background information that doesn't necessarily need to be read or understood. I hope it is of interest to others though. I posted similar things in threads over on UKVRRR, so apologies for those who have seen it all before.
When I first got ADSL, the sync speed settled on 4Mb/s. Compared to dial-up, it was amazing; I didn't give it much thought initially. But then I started thinking about basic physical stuff - the ADSL signal is a bunch of high frequencies riding on top of the baseband voice signal, so surely this means we need to think about basic transmission line theory? Then I thought about my house telephone wiring. While the microfilter was installed at the master socket, the extensions were connected to the removable lower half - as you'd expect. But, these extensions were surely acting as unterminated stubs, so would reflections from these interfere with the high frequency ADSL carriers? Presumably, at frequencies related to the length of the extension cables, notches in the high frequency response would occur?
To test this theory, I simply did something similar to what I suggested above - I removed the lower plate and plugged the 4 way flat extension cable into the test socket. At the end of the flat extension cable - in another room - I had my microfilter, then the modem and a Dect base station.
After making this change, the sync speed had doubled from 4 to 8Mb/s. That impressed me!
The next change was to move the master socket. Stupidly, it was in a bedroom - perhaps a legacy of a time when this old terrace had been split into 2 flats. I moved it to the cellar, which is below that bedroom (and the lounge). To do this, I bought the correct parts from a very handy eBay seller who has the same cable, connection boxes, jelly crimps, etc, as OpenReach use - there's no problem moving your master socket provided you don't mess it up - and if you do, OpenReach can charge you to fix it. But it's "breach of contract", rather than the widely believed "illegal".
The router was also moved down to the cellar - where I have a central cabinet to contain my IT gear and Cat5 patch panel - and the master socket was now alongside this. Effectively, this replaced the flat extension cable with proper twisted pair "drop wire", so maintained the correct characteristic impedance over the last 5-10 metres. And - perhaps surprisingly - the sync speed was now 12Mb/s. Maybe it's not all that surprising in reality - by the time the signal gets to you from the exchange, it's tiny. Anything that impairs the signal to noise ratio is going to reduce the potential data rate. The way that DSL automatically and dynamically adapts to the prevailing signal to noise ratio of the circuit really is very impressive - read up on it if you haven't before
Finally, I decided to replace the old BT master socket with a new one that contains the microfilter in the faceplate. These are quite interesting - read more about them here: https://www.telecomgreen.co.uk/engineeri...ided-tour/
The thing to notice is how sophisticated the filtering is. "Dangling" microfilters vary a lot in quality - https://www.adslnation.com/support/filters.php - so it's worth having a decent one.
I really wasn't expecting this to make much difference, but I was about to get FTTC, so wanted to do everything I could to optimise the signal path. It was only £13 from eBay, so cheap and easy to do. Upon installation, I found that my sync speed had risen from 12 to 14Mb/s - that surprised me, but obviously was good news.
When I did go for FTTC, Zen sent out the modem very promptly ahead of the go-live date. This was quite a posh unit, and so I couldn't resist trying it with my existing ADSL ahead of the change-over. And it got me another extra Mb/s or so (I'd have to look up the numbers when I get home).
So just to recap, I started out with 4Mb/s, and ended up with more like 15 or 16Mb/s, just as a result of making some easy changes to my wiring. OK, you could argue that moving the master socket was a bit of an effort, but it needed doing anyway, and it was dead easy once I'd bought the right parts (and a lot cheaper than paying OpenReach to do it). None of the wiring was actually faulty in any way, and indeed was configured the currently recommended way (not the "best" way, though) for a self-install, but simple measures made the performance so much better. All in return for some basic thinking about analogue electronics.
I can't understand why some (very good) engineers get "blind spots" with computer technology, because everything is analogue in the end
When I first got ADSL, the sync speed settled on 4Mb/s. Compared to dial-up, it was amazing; I didn't give it much thought initially. But then I started thinking about basic physical stuff - the ADSL signal is a bunch of high frequencies riding on top of the baseband voice signal, so surely this means we need to think about basic transmission line theory? Then I thought about my house telephone wiring. While the microfilter was installed at the master socket, the extensions were connected to the removable lower half - as you'd expect. But, these extensions were surely acting as unterminated stubs, so would reflections from these interfere with the high frequency ADSL carriers? Presumably, at frequencies related to the length of the extension cables, notches in the high frequency response would occur?
To test this theory, I simply did something similar to what I suggested above - I removed the lower plate and plugged the 4 way flat extension cable into the test socket. At the end of the flat extension cable - in another room - I had my microfilter, then the modem and a Dect base station.
After making this change, the sync speed had doubled from 4 to 8Mb/s. That impressed me!
The next change was to move the master socket. Stupidly, it was in a bedroom - perhaps a legacy of a time when this old terrace had been split into 2 flats. I moved it to the cellar, which is below that bedroom (and the lounge). To do this, I bought the correct parts from a very handy eBay seller who has the same cable, connection boxes, jelly crimps, etc, as OpenReach use - there's no problem moving your master socket provided you don't mess it up - and if you do, OpenReach can charge you to fix it. But it's "breach of contract", rather than the widely believed "illegal".
The router was also moved down to the cellar - where I have a central cabinet to contain my IT gear and Cat5 patch panel - and the master socket was now alongside this. Effectively, this replaced the flat extension cable with proper twisted pair "drop wire", so maintained the correct characteristic impedance over the last 5-10 metres. And - perhaps surprisingly - the sync speed was now 12Mb/s. Maybe it's not all that surprising in reality - by the time the signal gets to you from the exchange, it's tiny. Anything that impairs the signal to noise ratio is going to reduce the potential data rate. The way that DSL automatically and dynamically adapts to the prevailing signal to noise ratio of the circuit really is very impressive - read up on it if you haven't before
Finally, I decided to replace the old BT master socket with a new one that contains the microfilter in the faceplate. These are quite interesting - read more about them here: https://www.telecomgreen.co.uk/engineeri...ided-tour/
The thing to notice is how sophisticated the filtering is. "Dangling" microfilters vary a lot in quality - https://www.adslnation.com/support/filters.php - so it's worth having a decent one.
I really wasn't expecting this to make much difference, but I was about to get FTTC, so wanted to do everything I could to optimise the signal path. It was only £13 from eBay, so cheap and easy to do. Upon installation, I found that my sync speed had risen from 12 to 14Mb/s - that surprised me, but obviously was good news.
When I did go for FTTC, Zen sent out the modem very promptly ahead of the go-live date. This was quite a posh unit, and so I couldn't resist trying it with my existing ADSL ahead of the change-over. And it got me another extra Mb/s or so (I'd have to look up the numbers when I get home).
So just to recap, I started out with 4Mb/s, and ended up with more like 15 or 16Mb/s, just as a result of making some easy changes to my wiring. OK, you could argue that moving the master socket was a bit of an effort, but it needed doing anyway, and it was dead easy once I'd bought the right parts (and a lot cheaper than paying OpenReach to do it). None of the wiring was actually faulty in any way, and indeed was configured the currently recommended way (not the "best" way, though) for a self-install, but simple measures made the performance so much better. All in return for some basic thinking about analogue electronics.
I can't understand why some (very good) engineers get "blind spots" with computer technology, because everything is analogue in the end
