Interference & a Galvanic isolator
Hello
Does anyone have any suggestions in order to solve my interference problems. I suffer from much the same as a lot of people in urban areas I suppose, lots of RF interference. I have a loop antenna, made with M&P Ultraflex 10 coax, using the outer braid only, inside a 42" hula hoop with a WellGood amp. The loop is fixed on the gable end of the house, so quite high up. I was using it at the bottom of my 70 foot garden, the signals were quite good there and it was far enough away from anything electrical in my house, however someone in a neighbouring garden has something in their shed which switches on at about 16:20 everyday which causes lots of noise, not across the whole spectrum, mainly the lower half of the MW band, that interference is still present now although reduced. I do suffer all the time with wideband interference from somewhere else, as the image shows.
I don't think my own house is too blame, and I am powering the Kiwi with an official Apple 20w charger so I don't think the problem is there. Would a galvanic isolator help ?, I attach some screen shots. Does anyone have any suggestions please.
Comments
I had such massive problems, which look like your waterfall, with Powerline devices. Since I banned them from my house, things have got much better.
Perhaps you or your neighbours also have problems with network switches? Your neighbours' powerline or solar panels could also play a role.
Regards, Steffen
I also saw something similar on my KiwiSDR. This was due to the charger for a 12 volt car battery. I do not know what kind of charger it was, but I found out that the neighbor was charging the battery next to me. The KiwiSDR spectrum looked exactly like in the first screenshot. Unfortunately, many manufacturers of pulse devices save money and do not install anti-interference filters in their devices. I repair household appliances and sometimes I see this. I always try to install the missing capacitors and chokes in such devices.
Dear all,
this is why I have moved the receiving antennas as far away from buildings as possible. The antenna of my KiwiSDR #1 is 50 meters away. The antenna of KiwiSDR #2 is 250 meters away. The 75 ohm lines are buried about 40 cm. This is the only valid solution I have found to eliminate all this radio interference from domestic appliances using a switching power supply.
I also have 32 photovoltaic panels (12 kWp three-phase), which doesn't interfere with KiwiSDR reception, provided the installation is well filtered.
The neutral system on the electrical installation is IT (230 V). This means that there is no neutral and the mains power supply is symmetrical (two-phase).
I hope this helps. Happy RFI hunting. Best regards, Philippe
Not long ago I purchased an Apex Radio 303WA-2 from Japan. I also purchased this with it:
IT5050 アイソレーショントランス ApexRadio - BCL 広帯域受信 株式会社 アペックスラジオ 4573533000213
https://www.apexradio.co.jp/it5050_j.htmlIt does seem to clean up a lot of the noise you are seeing - or at the least reduce it significantly enough to be bearable.
Unfortunately, shipping these out of Japan isnt cheap as a third party has to buy this and ship to you. Not ideal or cheap. You can find these on eBay too.
Interference & a Galvanic isolator
https://forum.kiwisdr.com/index.php?p=/discussion/3520/interference-a-galvanic-isolatorI suspect you are largely seeing common mode noise on the coax transmission line. While the loop antenna might have good enough CM===> differential isolation, it is likely that current injected on it and/or the LAN/PS side, passing through the Kiwi 'ground' is resulting in unwanted responses.
That you are seeing this at MW and perhaps lower (it would be helpful if you had shown the spectrum with frequency display included - the waterfall display is almost worthless for this kind of diagnosis) almost guarantees that this coupling is not by way of inverse-square radiation into the loop.
The Kiwi has only 85 dB rejection of ground currents through it's ground plane so it doesn't take a lot of current flowing through the common connections and the PCB ground plane to raise the noise floor.
Whatever the noise source may be your effective antenna system is likely not simply the loop. You can try adding a flux-coupled low inter-turn capacitance isolation transformer at the Kiwi which might help but I'd recommend running an active antenna system with balanced line and having very high CMRR rejection instead of the single-ended coax.
You can find Open Source HW kit which you can order from JLCPCB on my web page.
Glenn n6gn
I'd be tempted to have a chat with your neighbour, mine have always been interested in finding out what could be causing such interference, but perhaps I'm lucky that many of them seem to be ex-engineers.
As previously mentioned, it's most likely a Chinese battery charger or similar, that hasn't got the mains filter components fitted.
Also, don't discount your own property, try and drop the main breaker if you can, whilst monitoring using batteries. It's surprising what can be overlooked.
Regards,
Martin