[Uram-rejections] Low Noise SMPSU

Sun Sep 17 14:45:38 BST 2017

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 Ok the thread might be driftiing off AR  a bit.

The post that you submitted to uk.radio.amateur.moderated has been rejected by a
moderator. 

This appears to the moderator to be off-topic for uk.radio.amateur.moderated
or has insufficient material related to amateur radio.

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============================================ Full text of your message follows
> From webstump at chiark.greenend.org.uk Sun Sep 17 14:15:01 2017
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> To: uk-radio-amateur-moderated at usenet.org.uk
> From: "Jim GM4DHJ ..." <kinvig.netta at ntlworld.com>
> Newsgroups: uk.radio.amateur.moderated
> Subject: Re: Low Noise SMPSU
> Date: Sun, 17 Sep 2017 14:14:58 +0100
> Organization: A noiseless patient Spider
> Message-ID: <oplsgk$2gp$1 at dont-email.me>
> References: <9ca75691-80bd-486e-8b37-7c8a316ae7a3 at googlegroups.com> <ophmo6$hd1$1 at jstuckle.eternal-september.org> <opjo8j$cge$1 at dont-email.me> <opkgkt$g62$1 at dont-email.me> <opl5ph$gp1$1 at dont-email.me>
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> 
> "mm0fmf" <none at invalid.com> wrote in message 
> news:opl5ph$gp1$1 at dont-email.me...
> > On 17/09/2017 01:46, Paul wrote:
> >> mm0fmf wrote:
> >>> On 16/09/2017 00:12, Jerry Stuckle wrote:
> >>>> On 9/15/2017 7:28 AM, m0afj at yahoo.co.uk wrote:
> >>>>> I'm looking for recommendations on a low noise SMPSU, 5A, 12V, small
> >>>>> form to power my mcHF SDR Tx/Rx.
> >>>>>
> >>>>> Cheers
> >>>>>
> >>>>> Tim M0AFJ
> >>>>>
> >>>>
> >>>> The problem is the low noise.  Switching supplies are light but put out
> >>>> a lot of RF.  The only "quiet" supplies I've found have lots of iron.
> >>>>
> >>>
> >>> An interesting generalisation but wrong. Switching supplies can be
> >>> made to be  RF quiet. There are plenty of supplies aimed at amateurs
> >>> in particular that are quiet.
> >>>
> >>> What is interesting is seeing that newsgroups are as noisy as
> >>> unsurpressed switching supplies in that more posts don't answer the
> >>> question than do. A significant noise factor!
> >>>
> >>> I don't know of any small supplies which was what the OP requested or
> >>> I'd have suggested them. Just to get back on topic. ;-)
> >>
> >> It's important to understand how they're designed,
> >> to know how easy it is to get a "dead quiet" one.
> >>
> >
> > [Lots of text snipped]
> >
> > From experience, the big difference in SMPS is whether the cheapskates in 
> > China fitted the suppression components or not. Typically, examining the 
> > PCB of AT/ATX supplies showed the silk screen layout for these components 
> > with wire links in place. Likewise the IEC connector would be a simple 
> > socket, not the type with integral filter.
> >
> > It's 20 years since I stopped working for a medical instrument 
> > manufacturer with EMC being one of my major tasks.
> 
> you may have known vic whyte then? .....
> 
> > Not only did the machines have to be electrically quiet themselves, they 
> > had to work on what was often quite noisy and dirty mains power. Meeting 
> > EMC requirements of the time (EN55022 etc.) was easy until the 
> > requirements of several CSA standards were applied that limited leakage 
> > current. That made filter selection challenging. It was always easier to 
> > specify supplies that met the requirements themselves than adding on 
> > suppression later.
> >
> > But as I say, 20 years has passed, so am I no longer in touch with the 
> > market to make recommendations. I can only assume cost cutting has got 
> > worse over that period to make the matter worse.
> >
> >
> bloody professionals ...... 
> 
> 
> 
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