450 Hz spacing noise + 53 Khz spacing noise on kiwisdr watterfall

Dear Kiwi community,

I am looking for advice regarding what appears on my Kiwisdr at the start of the 0 to 10 KHz band but can also have an impact higher up.

My Kiwisdr is located in the countryside, it is located in a house which I think is radioelectrically quiet.

The installation is composed as follows:

- 1 Kiwisdr connected to a 5 v power supply via the barrel port.

- 1 linear power supply (as much as possible), with a Talema transformer. https://fr.aliexpress.com/item/4000022726883.html?spm=a2g0o.order_list.order_list_main.15.21ef5e5bk1XbWI&gatewayAdapt=glo2fra

- 1 G5RV antenna 63 meters long approximately 12 meters from the ground for the central point.

- 1 GPS antenna with a small SMA extension to position it outside, and thus get the best possible view of the satellites.

No Ethernet connection to the internet box, but a wifi connection with a Tp-link dongle.

Between the antenna and the Kiwisdr input there is a Cross Country Wireless Receiver Front End Protection Unit (VLF/HF).


And yet I have just noticed that what looks like harmonics is present at the beginning of the band, and surely impacts my reception up to almost 30 MHz.

<a href="https://ibb.co/jfr1ShV"><img src="https://i.ibb.co/jfr1ShV/Low-KHz.png" alt="Low-KHz" border="0"></a>

The signals identified are as follows:

0.68KHz - 0.45KHz spacing

1.13KHz - 0.46KHz spacing

1.59KHz - 0.45KHz spacing

2.04KHz - 0.45KHz spacing

2.49KHz - 0.46KHz spacing

2.95KHz - 0.46 KHz spacing

3.40KHz - 0.45KHz spacing

3.85KHz - 0.45KHz spacing

There is therefore around 450 Hz difference between the signals.

If I'm not mistaken it would be a harmonic of order 9 of my 230-240VAC power supply at 50 Hz?

But why would it be received on Kiwisdr like a radio wave?

Another thing that is quite surprising and quite visible in the 2 MHz band, there seems to be present on the waterfall another harmonic (perhaps related?), which appears every 53 KHz around (spacing).

<a href="https://ibb.co/tHTc0qY"><img src="https://i.ibb.co/tHTc0qY/53-KHz.png" alt="53-KHz" border="0"></a>

Example: 2034.69 KHz







Have you ever encountered this phenomenon, and do you have any ideas or solutions to try to try to eliminate them?

It is sometimes easier to view the situation directly on the Kiwisdr concerned so here is the address of my Kiwisdr impacted by this problem.


With my best 73




  • A few things to try.

    Find a battery powered MW transistor radio with an internal ferrite rod antenna,

    Tune it to an empty bit of spectrum between broadcast stations where you can hear the distinctive noise of the interference.

    Turn off your mains supply at the main breaker. Dies the noise go away ? If so bring up each breaker one by one, until you hear the noise again, this will help you locate the offending item(s).

    If the noise doesn't go away, take a walk around your neighbourhood, and use the directional properties of the ferrite rod antenna to triangulate and track down the actual noise source. Then figure out how to best deal with it.

    It's probably a switched mode power supply of some sort, possibly a scooter or mobility device charger or similar. Does the noise follow any pattern which may help you figure out what it could be ?

    Incidentally, does your antenna have a decent ferrite cored choke balun installed ?



  • I just realised where I had heard a similar type of noise before.

    It was from a variable speed drive fan in an air sourced heat pump. The brushless fans had an electronically generated 3 phase invertor drive circuit built into them, that produced a modulated tone in the audio frequency range which varied with the speed they were running at. They in turn were fed from a high voltage switched mode power supply, operating at a much higher frequency.

    So it could be something similar, like a washing machine, or some other industrial or farm machinery.



  • Hi Bensay,

    Just visited and it seems that your high frequency band has much worse interference.

    I'm not an expert in this area, but in my experience trying to combat external interference the three most effective ways are grounding (plus an arrester), using chokes, and appropriate low-attenuation filters. If necessary, using a SW radio as a sniff tool for seeking RFI in proximity.

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