[ADXA] Switching PS / wall warts

[Jussi Eloranta]

Thank you for good advice. I will try one more power supply and then 
start playing with ferrites per your instructions.

Jussi (aa6kj)

On 11/17/25 5:12 PM, w5zn at w5zn.org wrote:

> The leads from the power supply are an antenna and will radiate. For 
> years I tried all kinds of toroids and ferrite cores, even ones that 
> were advertised as “Excellent RFI Suppression” which was simply not true.
>
> It wasn’t until Ward Silver, N0AX, was here at my station for a 
> contest and listened to my whining to the point he directed me to Jim 
> Brown, K9YC’s most excellent work
>
> Turns out I had two flaws in my effort; 1 – not using the correct 
> ferrite mix and 2- no using enough turns to create a high enough 
> impedance to choke off the RFI. Once I did start doing things right I 
> eliminated ALL of the noise in my shack. I don’t recall when you were 
> here in September 2024 if you were inside the shack but if so, you 
> probably saw every cable wrapped around one of those #31 toroids. The 
> photo sent in my last email was my external computer power supply lead 
> wrapped around one.
>
> Obviously you can search for a quite PS, but that is a difficult task 
> these days. You may want to try some of these toroids and wrap as many 
> turns around it as you can. You can purchase these from Mouser. It is 
> a Fair-Rite # 2631803802 and here’s the link to Mouser:
>
> https://www.mouser.com/ProductDetail/623-2631803802
>
> 73 Joel W5ZN / ZF2ZN
>
> *From:*adxa-bounces at mailman.qth.net <adxa-bounces at mailman.qth.net> *On 
> Behalf Of *Jussi Eloranta
> *Sent:* Monday, November 17, 2025 4:24 PM
> *To:* 'ADXA' <adxa at mailman.qth.net>
> *Subject:* Re: [ADXA] Switching PS / wall warts
>
> On 11/17/25 16:04, w5znjoel at gmail.com wrote:
>
>     What mix of ferrite??
>
>     Should be a #31. See photo
>
> I first tried a bunch of regular snap-ons which did very little. Then 
> I found - must admit not sure what the specs are - a ferrite ring in 
> my stash and tried that as well. So probably not the kind that it 
> needs to be... I think it is just easier to find a quiet PS - but who 
> knows!?
>
> Anyway, this device emits when it is just plugged in (no connection to 
> computer).  So, the ferrites should be around the AC cord? It also 
> radiates through the chassis as wrapping it in Al foil helped a bit. I 
> think a hammer - as suggested earlier - is the best tool for this one.
>
> But if anyone has suggestions for RF quiet 100W USB-C power supply, 
> let me know (if there is any???).
>
> Jussi (aa6kj)
>
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