Are metallic cable lengths the key?

A retired local BT engineer recently contacted us with some useful background data, whilst he was helping to improve the connection speed for a business near Hindhead, and included the following points:

  1. Cranleigh exchange covers a larger area than most other exchanges in Surrey, so it follows that we are likely to have some of the longest lines and, therefore, the slowest connections.
  2. BT’s FTTC could be the key to solving Surrey’s problem with slow connection speeds, because it effectively reduces line lengths.
  3. We can identify three broadband connection “speed points”: 20CN, 21CN and FTTC.

My reply included the following comments:

I think that you should add FTTP to your “speed points”, in fact probably as two “points”; one for BT’s slower asymmetric GPON version (max 330/30 Mbps), and a final one for symmetric point-to-point FTTP (max 1000/1000 Mbps).

As I recall, the upgrade to 21CN on my lines did improve connection speeds very slightly, but the more significant ADSL changes under customer control were (a) purchasing a modem which handled long lines better than the standard issue models (b) choosing an ISP/product with less contention e.g. Zen rather than BT or O2 (c) ensuring that internal wiring is optimised. I believe that (a) and (b) explain the fairly large difference in download speed between my two lines. However, when I switch between the two connections for work purposes, I do not really notice the difference until about 4pm (probably because the O2 connection is more symmetric), then O2 performance suffers noticeably. Somewhat ironically, the Zen connection is usually much better for leisure use such as shopping, but especially in evenings and weekends. Of course, a much larger improvement (on ADSL speeds) would be for BT to replace the decomposing aluminium cables with new copper, although doing this would be absurd in my opinion, since all copper will need to be replaced by fibre soon anyway.

My office connection (Zen) achieves throughput of about 1.8Mbps down and 0.3Mbps up with a 2wire 2700HGV modem. My backup connection is O2 using their standard modem: 1.2Mbps down, 0.6Mbps up. My estimate for FTTC is 4.6Mbps down and 0.9Mbps up on both lines, which I am told include aluminium cables in poor condition. My neighbours and I get connection problems quite frequently, often associated with crackly lines. Engineers tell us that these are mostly caused either by engineer work on an adjacent line disturbing a joint, especially in aluminium, or by water ingress. I currently have an intermittent fault documented in the comments here.

I can see from your map that Cranleigh exchange covers a large area by Surrey standards, which I had not known before. This then probably helps to explain why Cranleigh was the first rural exchange to be given FTTC in Surrey. Previously I had assumed this was purely down to the Ewhurst campaign. However, I doubt the Cranleigh coverage is large by national standards, and I believe that others on much longer lines than mine can get much better ADSL speeds if their infrastructure is in good condition and interference is low.

Finally, FTTC is not going to get my (or many other’s) connection up to the “superfast” speeds now generally agreed as the minimum acceptable, so it is certainly not the entire solution to Surrey’s problems. Also, the recent FTTC upgrade from “40Mbps” to “80Mbps” maximum makes no difference at all to those on long lines. See the information here, in particular the link to Mike Phillips’ graph might be informative.

I hope the above helps Phil when trying to improve broadband connections in and around Hindhead, and thank him for the information provided.


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