Monday, 11 July 2016

Interference

KPN Experia box internet modem
At the start of this year I did the 100DXCC in 100 days QRP challenge. At 5W power output there is not much chance you interfere with other appliances. But lately I had problems when I was using 50W or more on 80,60 and 40 meters. The problem is that my internet connection (not the WiFi connection with the router) was lost as soon I started transmitting. That means, no internet, no TV and no telephone. Especially the telephone disconnection can lead to dangerous situations in a emergency situation. So this problem had to be solved. Of course you first check everything at the shack. No earth loops, bad earth connections, bad connectors? I had the same problem on the horizontal loop so it could not be the antenna. The vertical antenna standing at least 10-15m from the house so any interference is almost not possible. I have a RF choke right below the autotuner at the base of the antenna to limit any RF on the coax. I noticed and measured a earth loop in the shack between the power supply and radio going trough the antennatuner.

So I disconnect that and fed my central earth point now through a ferrite ring to prevent my earth from radiating. It did help a tiny bit, internet did not disconnect immidiatly now but still after 5-10 seconds transmitting. So I made some interference precautions at the internet modem. Placed a netfilter between the power supply and net, although my shack is not physically connected so interference is almost not possible via electricity wires. Then I placed ferrite clamps on every wire at both sides. It didn't help anything at all! The only thing left was to disconnect cables one by one. Starting with the longest one a 10m CAT5e FTP cable to our TV. Without this cable I had no trouble at all, the internet did not disconnect. I plugged it in and had the trouble again but now after a while transmitting. So it definitely found the culprit. I immidiatly ordered a shielded CAT cable shown in the picture. This time as short as possible 7,5m. It actually was a little too short so I had to place the router modem elsewhere. I was afraid the WiFi signal would not reach the shack anymore now. But surprisingly the signal went up from good to very good. Anyway, I tested on 40m, 60m and 80m with a 80W PSK31 signal. Transmitting 3 times only give a few small hick ups at the TV. The internet connection was not lost, telephone and TV were ok. Hopefully the problem is solved now. When I have the horizontal loop up again in november I'll do more tests. For now at least I can work full output again.


4 comments:

  1. Hallo Bas, gelukkig dat het probleem nu opgelost is. Vervelende klacht. Hopelijk dat het bij dit blijft.
    73 Hans, PE1BVQ

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    1. Hallo Hans, ja je weet wat ik allemaal geprobeerd heb. Ik kan nu tenminste weer "QRO" zonder dat de TV etc. wegvalt. 73, Bas

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  2. Hallo Bas, ik had dat ook toen ik nog een Ziggo modem had [boven de 50 watt]. Inmiddels zijn alle kabels voorzien van ferrite clamps, maar dan ook echt alles. Nu met een KPN modem heb ik totaal geen last meer. Hoewel ik zelden boven de 50 watt zit, hooguit 30 watt. Maar meestal lager. 73 Paul PC4T

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    1. Kan me dat nog herinneren Paul, ik heb je destijds nog wat ferriet gestuurd. Ik denk ook zeker dat het type mode er mee te maken heeft. Hiervoor had k een zwart modem, die gaf geen problemen maar bij KPN vonden ze het nodig om het modem te vervangen. Ik geloof dat het samenging met digitale TV destijds. 73, Bas

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Thanks for your comment. Bedankt voor je reactie. 73, Bas