Good synch but terrible speeds?

[#1]

The connection feels a lot faster today and according to BTw it is improving:
-------------------------------
27-09-2015 13:40
BTw
Best Effort Test: -provides background information.
Download speedachieved during the test was - 5.37 Mbps
For your connection, the acceptable range of speeds is 2 Mbps-7.15 Mbps.
IP Profile for your line is - 6.06 Mbps
2. Upstream Test: -provides background information.
Upload speed achieved during the test was - 0.46Mbps
Additional Information:
Upstream Rate IP profile on your line is - 0.83 Mbps
------------------------
There are less errors being reported by the router (as far as I can tell):
Thomson Gateway
DSL Connection
27-09-2015 13:40
Link Information

Uptime: 1 day, 7:47:22
DSL Type: G.992.5 annex A
Maximum Bandwidth (Up/Down) [kbps/kbps]: 1,048 / 7,396
Bandwidth (Up/Down) [kbps/kbps]: 1,044 / 6,872
Data Transferred (Sent/Received) [MB/MB]: 52.83 / 300.13
Output Power (Up/Down) [dBm]: 12.5 / 20.0
Line Attenuation (Up/Down) [dB]: 23.0 / 40.0
SN Margin (Up/Down) [dB]: 6.0 / 6.0
Vendor ID (Local/Remote): TMMB / IFTN
Loss of Framing (Local/Remote): 0 / 0
Loss of Signal (Local/Remote): 4 / 0
Loss of Power (Local/Remote): 0 / 0
Loss of Link (Remote): 0
Error Seconds (Local/Remote): 65,536 / 0
FEC Errors (Up/Down): 544 / 1,223,478
CRC Errors (Up/Down): 258 / 116
HEC Errors (Up/Down): 365 / 882
yet TBB test still looks lousy:

Could this anomaly be down to my AV software (Kaspersky)?

[#2]

I can't figure this out at all.
Speeds suddenly crawling again so I ran the BTw test again, about 15 minutes after the last one:
-------------------------
Best Effort Test: -provides background information.

Download speedachieved during the test was - 1.07 Mbps
For your connection, the acceptable range of speeds is 2 Mbps-7.15 Mbps.
IP Profile for your line is - 6.06 Mbps
2. Upstream Test: -provides background information.

Upload speed achieved during the test was - 0.61Mbps
Additional Information:
Upstream Rate IP profile on your line is - 0.83 Mbps
------------------------
How can it change so rapidly ? Routerstats reports a brief loss of synch around the time I did the TBB test but the router stayed connected.
I have an unused one of these:
http://www.amazon.co.uk/product-reviews/B001OAX9XU
Any ideas if this would be easy to set up for Plusnet?
The reviews on Amazon are a bit mixed, to say the least!

[#3]

Setting up another router should be fairly straightforward, it should only need your connection details to establish an Internet connection.
Your latest stats had only a few CRC (and HEC) errors, while connected at a slightly slower speed, and with a higher SNR margin (at least when the stats were taken). They looked OK apart from the low speed.
I suppose even your TBB speedtest result that achieved 6Mb stayed low for a while at the start of the download, so that might be something related to your computer and its software.

[#4]

I'm going to try the speedtests again through a laptop in attempt to rule out my main PC software.
I will also attempt a direct wired connection, bypassing the wireless  ( a bit of a pain as it will involve moving furniture around..!).
It's the inconsistency of the speed test results I find maddening - up one minute, down the next!

[#5]

Quote from: Bookworms

I will also attempt a direct wired connection, bypassing the wireless  ( a bit of a pain as it will involve moving furniture around..!).

Make sure you switch off the wireless adapter - sometimes it will keep trying to connect wireless even when connected  by cable
thus confusing/slowing down the router.

[#6]

It is not so much trying to connect or confusing the router, but rather that unless the wifi is disabled on the PC, then the PC is connected via BOTH wifi and Ethernet to the router concurrently.
There is then confusion within the PC over which connection it will use out of preference.  Unless each interface has different connection metrics, it will use the link which has been the most responsive the longest.  Therefore if a PC which is otherwise connected over wifi has a cable plugged into it, unless the wifi interface is disabled, there is every possibility that communication will continue over wifi, rather than (as many presume) over the Ethernet cable.

[#7]

Hmm, it looks like this could have been due to something wrong with my main desktop PC set up.
I carried out the BTw speedtest on both it and my old laptop within the space of a few minutes - the laptop results were ok (around 6Mb) whereas the PC results were below 1Mb.
I've cleared internet cache, run Ccleaner and rebooted my desktop and that seems (for the moment at least) to have cured the speed problem.
It's been a few weeks since I did a cold reboot on this system - I normally leave it on standby. 
Now...how to work out what on my PC was causing the problem.
I guess my mini Netgear wireless dongle is the most likely culprit?

[#8]

...and possibly that even though you plugged a cable into the PC, it was still connecting (in preference) over wifi? 
Worry not, it is good to hear that you've reached a conclusion.

[#9]

Quote from: Townman

...and possibly that even though you plugged a cable into the PC, it was still connecting (in preference) over wifi?

Well, actually I haven't yet tried connecting the PC directly via cable. 
If the speed problem returns I will be sure to do so.
Thanks to everyone for your comments.