These days, the internet is connected to just about everything electronic in the modern house, from TVs to refrigerators.
My family and I are serious internet users, so when the new QTH was being built, I had the electricians run Cat6 cable to 14 outlets throughout the house.
I installed a 24 port network IP switch in a dedicated server cabinet in the garage and connected my NBN modem to it. All good so far – lots of pretty lights on the switch, and all the TVs, PCs, Sonos music systems and Bose internet radios worked perfectly.
All was great….until I put my HF rig on 20m….to be confronted with this:
S7 spikes about every 60 kHz
There was a lovely birdie right on 14150 kHz. Armed with my trusty Sony portable HF receiver, I wandered about the house listening for the QRM. The signal sounded like a multi tone data stream. Sure enough, the signal was strong at all the Cat 6 wall outlets and the patch cables to the equipment. It was almost full scale at the switch itself.
I confirmed the problem by turning the switch off. The QRM stopped.
After some head scratching, I decided to do a system reconfiguration, with the aim of reducing the number of Cat6 ports used in the house, and therefore the amount of noise generated on 20m.
I managed to reduce the ports I needed down to 10 – with a particular focus on eliminating the ports with the longest runs of Cat6 cable, and the wall outlets closest to the 20m antenna.
I replaced the 24 port switch with an 8 port model from a different company. With this and 3 spare ports on the NBN modem, I had enough network capacity.
The QRM was now down to S3, but it was still there.
So, I consulted the chaps at QRM Guru (www.qrm.guru) and purchased a number of clip on ferrites and ferrite rings.
I put rings with at least 6 turns of cable on every patch cable coming from the switch, every cable from the NBN modem and every patch cable at the Cat 6 wall outlets throughout the house. I also used clip on ferrites on all the cables coming from the patch panel.
Ferrites everywhere – note the new 8 port switch on top of its 24 port predecessor
Success! The QRM was down to S1 now.
The moral of the story?…. Ferrites work and persistence pays off.
Order your kits here.