laptop psu rfi - Page 1
Forum section: electronics / rf-microwave

author: p.larner
author_rank: Frequent Contributor
timestamp: October 23, 2023, 06:37:47 pm
content: my lappy power brick gives s9+ of noise on most hf bands,it already has ferrites on the lead to the pc,would putting 2 shottky diodes back to back in the power lead(240v) earth wire?.

author: radiolistener
author_rank: Super Contributor
timestamp: October 24, 2023, 06:03:53 am
content: the only way to fix it is to put it into garbage bin and buy a new good quality PSU...Usually such cheap PSU have many issues, not only RFI noise, so if you try to fix it you will trap to other issues, such as bad transformer with parasite capacitance, bad pcb layout, bad capacitors, etc. So it will be more easy to replace entire PSU, than fix it.Also note that any SMPS PSU has some degree of RFI noise, but usually for good quality PSU it is low enough to ignore it. If you want to elimnate it at all, you can use linear PSU.

author: p.larner
author_rank: Frequent Contributor
timestamp: October 24, 2023, 07:21:48 am
content: well i took it apart and the can/cover of a 470uf/25v cap fell out,strange as the can top wasnt buldged and the main body as in one piece,i replaced it,the old one measured 23nf,didnt bother checking esr,i have also removed the mains input connector and fitted an input filter with incorperated fuse from some old test gear,,the plastic case of the psu is covered in aluminium tape and electricaly bonded to the mains filter earth wire,will try it later,got to be better than s9+ of noise i hope? 73,

author: Andy Chee
author_rank: Super Contributor
timestamp: October 24, 2023, 08:07:23 am
content: Checkout GM3SEK's mains filterhttps://gm3sek.com/2019/10/11/clean-up-your-shack-2019/

author: p.larner
author_rank: Frequent Contributor
timestamp: October 24, 2023, 09:24:32 am
content: my god thats one of the worst disjointed websites i have seen in years,

author: max-bit
author_rank: Frequent Contributor
timestamp: October 25, 2023, 08:46:23 am
content: Unfortunately, modern (even the best) switching power supplies are a great source of all kinds of interference, especially in the band up to about 100 MHz.Of course, the better ones have a lower level of interference, the worse ones have a higher one, and removing them is expensive.However, manufacturers of amateur radio equipment have been using converters in their devices for a long time. But there's nothing like a good (albeit large) linear power supply.

author: p.larner
author_rank: Frequent Contributor
timestamp: October 25, 2023, 07:44:31 pm
content: well it has helped,the broadband noise has gone from s9+ to s3 so worth the effort,als good job i opened it or wouldnt of seen the naked cap.

author: A.Z.
author_rank: Super Contributor
timestamp: October 29, 2023, 06:46:07 am
content: Quote from: Andy Chee on October 24, 2023, 08:07:23 amthat filter is nice, and if it doesn't suffice one may try adding this circuithttps://www.ka7oei.com/syn_blank.htmla two or three stage version should take care of noise in most cased

author: pienari
author_rank: Regular Contributor
timestamp: November 04, 2023, 06:34:38 pm
content: I tested a few days ago and the HP Probook laptop psu gives rfi to a low HF frequency when charging the battery, when the battery is full the interference disappears.But.. the new Chinese phone fast charger blows S9 noise from 1 to 30MHz, up to 70MHz S4.I made a filter on the power line and now the noise is not so loud at HF frequencies

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: November 11, 2023, 11:32:09 pm
content: Ethernet Cables can cause a lot of HF noise also. don't know if you use them.