Often I looking for some info on a amateur radio project I interested in, I do some searching on the web, one site I usually end up on and finding some good info is George Smart's (M1GEO) blog. He trying all sorts of stuff with the hobby (and general electronics too) and find his posts well documented with what the particular subject is about and what he trying to achieve in it and what the results are. Always worth a look here. One such example was compiling up up WSJT for Linux, I found George's article most helpful and I was able to successfully compile WSJT on Linux myself following his instructions.
https://www.george-smart.co.uk/radio/
Wednesday, April 25, 2018
Wednesday, April 11, 2018
RFI from Foxtel IQ2 STB's on 10m & 6m bands
I noticed hearing modulated signals across 29 MHz band and 52-53 MHz bands when scanning the FM segments from time to time, not clean carriers but data modulated carriers appearing then disappearing. By accident, I just happening to hear this occurring one day and by chance doors were open in the house where I could see through doorways to the TV set where the XYL was flicking through Foxtel channels. OMG, the modulation on the signal varying as channels are being changed, here was the culprit, our Foxtel IQ2 STB (set-top-box).
I got out the Uniden handheld scanner and did some sniffing around the STB, but no, it seems to be radiating from the LED flat panel TV, turned power off to the TV but noise still radiating, unplug power cable from TV and noise still there, unplug HDMI cable to Foxtel STB, then RFI signal drops off drastically.
Sniff closer to Foxtel box, very strong signal from the ethernet RJ45 cable and the HDMI cable. Remove both cables and noise almost non-existant. sniff the power cord at the rear of Foxtel STB and noise still very low, plugin the HDMI and ethernet cables one at a time, pretty equally as strong.
I noticed it detected noise on 2m band too, but much lower levels than that of 10m and 6m bands.
Outcome, the Foxtel box itself not radiating but very bad when HDMI cable plugged into a LED flat panel TV, as it using the TV as a RFI antenna. As a secondary source of RFI it using the Ethernet RJ45 cable as a nice antenna too. I think from memory the IQ2 box made by Pace.
Solution, grabbed my box of various sized ferrite clipon cores, added 7mm ID and 9mm ID cores on the power, RJ-45 and HDMI cables, closest to the rear of the Foxtel IQ2 box, this suppressed the RFI sufficiently, in terms of 10m and 6m bands, could now only receive RFI up to about 1 metre from the STB, whereas my transceiver antenna could hear it from 20 metres away. I also tried clamping some ferrite cores over the two coax leads running to the satellite dish LNA but that made absolutely no difference, so RFI not radiating back out via coaxes, that I could see.
I got out the Uniden handheld scanner and did some sniffing around the STB, but no, it seems to be radiating from the LED flat panel TV, turned power off to the TV but noise still radiating, unplug power cable from TV and noise still there, unplug HDMI cable to Foxtel STB, then RFI signal drops off drastically.
Sniff closer to Foxtel box, very strong signal from the ethernet RJ45 cable and the HDMI cable. Remove both cables and noise almost non-existant. sniff the power cord at the rear of Foxtel STB and noise still very low, plugin the HDMI and ethernet cables one at a time, pretty equally as strong.
I noticed it detected noise on 2m band too, but much lower levels than that of 10m and 6m bands.
Outcome, the Foxtel box itself not radiating but very bad when HDMI cable plugged into a LED flat panel TV, as it using the TV as a RFI antenna. As a secondary source of RFI it using the Ethernet RJ45 cable as a nice antenna too. I think from memory the IQ2 box made by Pace.
Solution, grabbed my box of various sized ferrite clipon cores, added 7mm ID and 9mm ID cores on the power, RJ-45 and HDMI cables, closest to the rear of the Foxtel IQ2 box, this suppressed the RFI sufficiently, in terms of 10m and 6m bands, could now only receive RFI up to about 1 metre from the STB, whereas my transceiver antenna could hear it from 20 metres away. I also tried clamping some ferrite cores over the two coax leads running to the satellite dish LNA but that made absolutely no difference, so RFI not radiating back out via coaxes, that I could see.
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