Welcome to the world of EMC.
Many devices especially those cheap ones coming from Asia do not fulfil the requirements of the EMC-directive (Europe) or FCC (USA). They produce to much noise on the power-lines, the power-lines radiate this noise and you hear the harmonics of the switching-frequency of your (or your neighbours) power-supply.
An other version of these noise-generator is called PLC (Power Line Communication). PLC misuses the power lines for data communication and because power lines are not made for data communication they radiate the PLC signal.
You did not say which frequency range is disturbed but I assume its LF and MF and maybe SW. At first try to switch off (better: unplug) all devices and look whether the noise disappears. The worst noise producer I ever had was a small (5V,1A) power supply of a network switch.
If that doesn't work start a "Fox Hunt" with an AM-receiver and a ferrite antenna. The noise does not need to come out of your house, maybe its your neighbour.
Ferrite cores or chokes do not work good on low frequencies (LF, MF) their inductivity is to low.
Reason: No reason
RFsystems DX-10 (14kHz to 50MHz), resistive splitter 1/4, 1:16 transformer on Hi-Z of RSP2
ICOM Discone AH-8000 (10MHz to 2GHz)
12m above ground
That depends on how the noise comes into your receiver. Some of the countermeasures have already been mentioned.K4ZOT wrote:OK - thanks very much. Is there a way of filtering out some of the screen noise with RSP2?
1. Good grounding of receiver and coaxial cable shield
2. Common mode chokes at the antenna input of the receiver (no snap on ferrites, but large wideband toroids)
3. Line filters for computers, monitors, switched power supplies in the house
4. Winding USB cables through large toroids
5. Bigger distance between antenna and noise sources
It is difficult to predict which countermeasures help unless the cause of the noise is clear. It can be a sort of magnetic induction into the coaxial cable or direct catch by the antenna. 60 kHz spacing is an indicator for switched power supplies in the vicinity. Item 2. should help when the noise is induced into the coax cable, but is not present in the antenna. Additionally item 3. should help when your own computers, monitors or other devices in the house create the noise. Everything is useless when the noise is picked up by the antenna itself from your neighbourhood.
Reason: No reason