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Author Topic: Some more adventures in RFI reduction  (Read 514 times)

Offline ChrisSmolinski

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Some more adventures in RFI reduction
« on: April 19, 2018, 2137 UTC »
One issue I have with copying the ISS SSTV transmissions on 145.8 MHz is that I had lots of RFI right on the frequency. It also appeared on 11m, although somewhat weaker.  I traced it to the ethernet wiring in the shack, by using the AirSpyHF+ connected to the laptop, and with just a small whip antenna (I use this setup often for sniffing around the house for RFI sources).

I have 4 computers, plus a WiFi router to cover the upstairs, and a weather station all plugged into the switch. There's also ethernet cables going to the netSDR and AFE822x SDRs. I don't use WiFi here as the cablemodem  and main WiFi router are downstairs at the extreme other end of the house, the signal strength is low. Plus wired ethernet is higher speed. The cable that runs from the switch to the main router was already shielded (since part of it runs outside the house, and it is a long run, 100 ft).

I decided to take a gamble, and replace the switch, as well as all the other ethernet wiring with shielded cables. This would also be an opportunity to upgrade to a faster switch, the old one was 100 Mb.  I bought a gigabit switch (tp-link TL-SG108), which not only has shielded ports, but is also in a metal box. I hoped that would further reduce RFI. And indeed that's the case, the RFI issue on 145.8 MHz is almost completely gone. What remains is from the WiFi router up here, which happens to be located near the window that the VHF/UHF discone is mounted outside. I think moving the router further away may help with that. And it is completely gone on 11 meters.

And as a bonus, with the faster switch, my download speeds went from 90 Mb to 180 Mb.  ;D

If you still use wired ethernet, you may want to investigate if this is a source of RFI.
Chris Smolinski
Westminster, MD
eQSLs appreciated! csmolinski@blackcatsystems.com
NRD 545 / netSDR / AFE822x / AirSpy HF+ / KiwiSDR / 670 ft horizontal loop / 500 ft northeast beverage / 58 ft T2FD / 300 ft south beverage / 43m / 20m / 10m  dipoles / Crossed Parallel Loop

Offline redhat

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Re: Some more adventures in RFI reduction
« Reply #1 on: April 19, 2018, 2247 UTC »
Thats why I buy commercial switches and routers in metal boxes....with rack ears :)

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Offline jFarley

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Re: Some more adventures in RFI reduction
« Reply #2 on: April 20, 2018, 1305 UTC »
It's a never ending battle; congratulations!
Joe Farley, Near Chicago
SDR-IQ / R8 / R7
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Offline ChrisSmolinski

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Re: Some more adventures in RFI reduction
« Reply #3 on: April 20, 2018, 1317 UTC »
It's a never ending battle; congratulations!

Thanks. Now I am dealing with some critter that chewed through the cat6 cable that runs out to the crossed parallel loop. It really is a never ending battle.
Chris Smolinski
Westminster, MD
eQSLs appreciated! csmolinski@blackcatsystems.com
NRD 545 / netSDR / AFE822x / AirSpy HF+ / KiwiSDR / 670 ft horizontal loop / 500 ft northeast beverage / 58 ft T2FD / 300 ft south beverage / 43m / 20m / 10m  dipoles / Crossed Parallel Loop