Amateur radio interference to NBN (VDSL2) connection in Australia

From time to time I transmit on the 80m and 40m band. The frequencies in these bands overlap with the frequencies utilised by the NBN here in Australia. The NBN in Australia utilises VDSL2 often using the existing copper phone line for the final stretch from the node to the premises – in my case the final 700m.

When I first started transmitting I noticed my internet connection would drop. After a bit of experimentation I found that I can see the interference in the admin screen of my modem (FRITZ!Box 7490).

Here is what the SNR graphs look like steady state

When I transmit on 80m or 40m there is plenty of interference introduced by the transmitter as seen in the following screenshots.

Test transmission on 80m
Test transmission on 40m

I have just finish studying for my Advanced licence and so have had the ear of a few people with the extensive knowledge on all things interference lately. They kindly suggested winding the phone line around ferrite rods which I tried (clump of 4 rods with 5m of phone line wound around it) but the internet still drops when I test transmit 100W CW, have also added various values of capacitor in shunt between red and green phone line. As can be seen from the following screen shots, the various capacitance have some fairly dramatic impacts on the bandwidth that is available to the connection and hence what speeds I get on my VDSL2 (NBN) connection.

20,000pF resulted in 11.05MBits Down and 1.45kBits Up

20,000pF in shunt – really knocks the internet connection around. notice only have 1 download and 1 upload band

10,000pF results in 14.MBits Down and 3MBits Up

1,000pF results in 26MBits Down and9.7MBIts up

33pF its getting back to normal now 41MBits Down and 11.5MBits Up.

I hope there are others out there that find this page and it can assist in identifying issues you may have and what doesn’t seem to work for me. If you have any suggestions on what will fix this persistent issue I’m all ears.

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