RFI

A page created to document investigations into RFI when using the RX-888 MKII

 

When the WellGood Loop was attached in 2024 there were 2 types of interference observed

Issue 1: Noise jump from 8.5MHz to 12MHz
Issue 2: Noise spikes from 12MHz

 

Both issues were found in this video by John Rogers (M0JAV) EMF Chair at the RSGB https://www.youtube.com/watch?v=z-isgEyF_V4&t=1s

Issue 1: Appears to be VDSL band ‘U2’ which is 8.5MHz to 12MHz (20 mins into video)

More details about VDSL is detailed here https://rsgb.org/main/files/2019/01/EMC-Leaflet-15-VSDL-v2-January-2018.pdf )

Issue 2: Appears to be power supply related (33.26 mins into video)

 

18th January 2025

Reconnected the RX-888 MKII to the WellGood v4.1 Loop

The Spectrum has changed since last year

 

I recorded my screen when I turned on my TP-Link AX5400 router. Around 1m 55s into the video the noise levels jump – this was at the point where the router was establishing an internet connection https://www.youtube.com/watch?v=B-7ubJTUZus

 

19th January 2025

I turned off everything in the house apart from my PC with the RX888 attached, bias-t box & Filter-Preamp (both use the same PSU) and TV monitor.

High noise levels remain with spikes relating to PSU noise evident
This shows the spectrum without the Turn Island Systems Preamp-Filter attached. The signal strength is lower

After reconnecting devices I noticed a significant noise increase when I connected the PC with the RX888 attached via ethernet to the router. The noise mirrors what was seen on the video linked to yesterday.  I tried 4 different ethernet patch cables and each one caused the noise to appear.

 

Summary: The first screenshot with nothing else turned on highlighted PSU spikes appearing. This could be caused by either the PSU in the Computer or the PSU used to power the bias-t & Filter-Preamp.  The noise increase when connecting the ethernet cable to the Computer could indicate poor shielding on the Computer.

Next steps

Try a 12v Linear Regulated PSU for the bias-t/ Filter-Preamp? https://pulsardevelopments.com/power-supplies/linear.html?output_volt_conv_dc=132

The computer power lead already has 2 ferrites on it – is there any other shielding I can try for the computer, specifically around the PSU and ethernet connector?

VDSL – ?

(21st January 2025) Purchased a www.rfcomms.co.uk Choke www.ebay.co.uk/itm/235873493937

Is there anyway of checking if RFI is coming from the wall power sockets?

 

20th January 2025

Thought I’d try a different power lead for my HP Prodesk 400 G5 MT, with a TDK ZCAT3035-1330 clip-on ferrite and a generic ferrite fitted at both ends of the 1m cable

The noise remains

I then decided to test an SDRPlay RSP1A using the WellGood and Filter-Preamp. The RSP1A has a maximum of 10MHz bandwidth so I’ve taken a number of screenshots to show the full HF band. Interesting that image 1 with a centre frequency of 5MHz shows a lower noise floor, whereas image 2 shows the noise floor jumps up around 5.75MHz.

 

 

Link to my RX-888 MKII Poject page www.airband-radio.co.uk/rx888