开云体育

ctrl + shift + ? for shortcuts
© 2025 开云体育
  1. Softrock40
  2. Topics

a day of tracking down and eliminating interference

 

Tony's revamping of the HF to LF SDR, and its arrival today, caused me to further track down interference since it was worse on LF.? I've managed to find and eliminate almost all such sources now with one exception:? I run an LED "fluorescent" light in the kitchen.? It's a small unit with obvious switching power supply within.? Unfortunately, it causes interference around 4 Mhz.? A trick I tried with my cordless phone base, also causing interference, and that trick was wrapping the power supply wires through a couple of ferrite cores, is not working with the LED fluorescent.? It continues to cause a buzz in HF.? It's a safety hazard to one of the occupants living here not to have the light plugged in 24/7, so I would appreciate any suggestions you might have.

Thanks!

Jon
 

A problem with these "fluorescent tube" LEDs is that the tube itself acts as an antenna and radiates. Unless the switching power supply is very well made, which is not very common,? its pulses are very steep and not controlled and so they produce interference that is radiated and conducted. The conducted one can be stopped with the ferrites at the input but the radiated one is quite difficult to eliminate, you need to filter the power supply output to the LEDS. The solution could be to change the power supply (not always possible) or changing the whole fixture.

Regards,

Ignacio EB4APL

El 23/06/2021 a las 1:23, JonI via groups.io escribió:
Tony's revamping of the HF to LF SDR, and its arrival today, caused me to further track down interference since it was worse on LF.? I've managed to find and eliminate almost all such sources now with one exception:? I run an LED "fluorescent" light in the kitchen.? It's a small unit with obvious switching power supply within. Unfortunately, it causes interference around 4 Mhz.? A trick I tried with my cordless phone base, also causing interference, and that trick was wrapping the power supply wires through a couple of ferrite cores, is not working with the LED fluorescent.? It continues to cause a buzz in HF.? It's a safety hazard to one of the occupants living here not to have the light plugged in 24/7, so I would appreciate any suggestions you might have.

Thanks!

Jon





--
El software de antivirus Avast ha analizado este correo electrónico en busca de virus.
 

Thanks, Ignacio, not good news for sure.? I was thinking of making and installing an AC line filter in line with the cord since the snap over ferrite wasn't doing anything, but not sure now if it would do any good.? I may be able to access the lamp internally as there are screws at both ends.? Can you suggest a schematic for a filter circuit I may be able to try for the switching supply to LED output?

Thanks!

On 6/23/21 5:43 AM, EB4APL wrote:
A problem with these "fluorescent tube" LEDs is that the tube itself acts as an antenna and radiates. Unless the switching power supply is very well made, which is not very common,? its pulses are very steep and not controlled and so they produce interference that is radiated and conducted. The conducted one can be stopped with the ferrites at the input but the radiated one is quite difficult to eliminate, you need to filter the power supply output to the LEDS. The solution could be to change the power supply (not always possible) or changing the whole fixture.

Regards,

Ignacio EB4APL


El 23/06/2021 a las 1:23, JonI via groups.io escribió:
Tony's revamping of the HF to LF SDR, and its arrival today, caused me to further track down interference since it was worse on LF.? I've managed to find and eliminate almost all such sources now with one exception:? I run an LED "fluorescent" light in the kitchen.? It's a small unit with obvious switching power supply within. Unfortunately, it causes interference around 4 Mhz.? A trick I tried with my cordless phone base, also causing interference, and that trick was wrapping the power supply wires through a couple of ferrite cores, is not working with the LED fluorescent.? It continues to cause a buzz in HF.? It's a safety hazard to one of the occupants living here not to have the light plugged in 24/7, so I would appreciate any suggestions you might have.

Thanks!

Jon
 

Possibly replace the lamp with one that uses an incandescent bulb?
Bob Gass
 

Surplus EMI filters work pretty good at suppressing the noise. This was my fix for Rural King shop lights that I installed in some of my repeater sites where I also have HF remote stations. I tried ferrites on the ac cord but that was a waste of time and ferrites.

Bob N4FV
 

Thanks, Bob.? Although my light is a tiny 15 watt one, I still want to try one of the filters inline and glad you specified filter type as I wanted to install a 2 stage one.? I also have a cordless phone base that wreaks havoc around 5 Mhz.? It uses a "walwart" for power.? I wound some of the wire between the walwart and cordless base through two snap ferrites that seemed to have reduced the interference to almost nothing.? However, since these ferrites were borrowed from something else, I'd like to return them.? I wonder if an inline filter could be used here as well, either between the walwart and cordless base or between outlet and walwart?? Can the Corcom units you mentioned also be used for DC?

On 6/24/21 10:33 AM, Bob Gass via groups.io wrote:
Surplus EMI filters work pretty good at suppressing the noise. This was my fix for Rural King shop lights that I installed in some of my repeater sites where I also have HF remote stations. I tried ferrites on the ac cord but that was a waste of time and ferrites.

Bob N4FV

1 - 6 of 6