RF Quiet Wall warts

On Friday, August 25, 2017 at 11:15:07 AM UTC-4, Martin Riddle wrote:
> On Fri, 25 Aug 2017 06:25:49 -0700 (PDT), George Herold
> <gherold@teachspin.com> wrote:
> 
> >On Thursday, August 24, 2017 at 9:35:20 PM UTC-4, Martin Riddle wrote:
> >> It's been a year or two since I listend to AM Radio, and in that time
> >> theres a new Roku box and linksys router.  Well, I couldn't hear
> >> anything  on the AM band when I checked a week ago. So the quest was
> >> to find the culprits. Its these SMPS wall warts, they literly wipe out
> >> the entire AM band, and also some chinese LED lights( 15w equiv
> >> Grimaldi's ).
> >> Tossing the led lights are easy, the wall warts not so.
> >> I found the old DSL modem transformer wall wart and that is quiet.
> >> Perusing the Innernet, I see some mention Apple supplies and the
> >> Powerstream SMPS supplies are quiet too, any one here with experiance
> >> with them? 
> >> 
> >> Cheers
> >
> >Do you know if the interference is radiated or conducted?  
> >(Tin foil hat (copper tape) for one, a ferrite choke thing for the 
> >other?) 
> >
> >George H. 
> 
> Probably Conducted=> then radiated by the power lines.
> The Favorite Fairite Bead does very little on the DC output lead.
> 
> I could try an Isobar power tap, to see.
> 
> I have a  Netgear Gbit switch that the smps Wall wart is pretty quiet
> in comparision. As well as a Logitech speake rsmps  wallwart.
> 
> Cheers
> Cheers

Well if the ferrite didn't work you could try a shield.  I made 
this power supply with DC-DC converters.  Nice layout and ground 
planes, but still switching noise.  I put copper tape hats on the 
converters and that knocked it down.  

George H.   

"George Herold" <gherold@teachspin.com> wrote in message 
news:558d2f39-35a3-4bf4-a1dc-b39334ce98d7@googlegroups.com...
> Well if the ferrite didn't work you could try a shield.  I made
> this power supply with DC-DC converters.  Nice layout and ground
> planes, but still switching noise.  I put copper tape hats on the
> converters and that knocked it down.

FWIW, ferrites rarely do more than 3-6dB of attenuation.  A long stack of 
them, maybe over 10dB.  The reason is, if there's no shunting impedance (to 
ground, or, more generally, to the other cable coming out of the box), it's 
an impedance divider against the capacitance-to-space of the cables in 
question.

It's probably even more basic than shielding: you need to start with a 
shunting impedance in the first place.  This is usually a 1nF Y1 ceramic cap 
between rectified mains and secondary grounds.

A lot of USB charger style warts have even less capacitance.  It's not clear 
to me if they have a shielded transformer (unlikely, but possible; I need to 
take one apart some time), or if they really just don't care (there's very 
little radiation from a wall wart, if there's no charging cable and load 
plugged in ;-) ).  They don't usually have a CMC, or just a small one and no 
other Y caps if they do.  (Again, not good for much, without a shunting 
impedance to help out.)

So, after adding a few caps and chokes: your next goal is shielding, 
surrounding the PSU core with chokes, and shunting all inputs and outputs 
with caps to the shield.  (Shield should also be earthed, because leakage 
current and safety.)

Tim

-- 
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Contract Design
Website: http://seventransistorlabs.com 

On Friday, August 25, 2017 at 2:04:20 PM UTC-4, Tim Williams wrote:
> "George Herold" <gherold@teachspin.com> wrote in message 
> news:558d2f39-35a3-4bf4-a1dc-b39334ce98d7@googlegroups.com...
> > Well if the ferrite didn't work you could try a shield.  I made
> > this power supply with DC-DC converters.  Nice layout and ground
> > planes, but still switching noise.  I put copper tape hats on the
> > converters and that knocked it down.
> 
> FWIW, ferrites rarely do more than 3-6dB of attenuation.  A long stack of 
> them, maybe over 10dB.  The reason is, if there's no shunting impedance (to 
> ground, or, more generally, to the other cable coming out of the box), it's 
> an impedance divider against the capacitance-to-space of the cables in 
> question.
That makes sense. I do a lot of hunt and pecking when dealing with 
interference.  Here's my fav, ferrite choking a usb line.  

https://www.dropbox.com/s/twhtnr6mzq7mwil/ferrite.JPG?dl=0

It worked and I moved on.  :^) 

George H. 
> 
> It's probably even more basic than shielding: you need to start with a 
> shunting impedance in the first place.  This is usually a 1nF Y1 ceramic cap 
> between rectified mains and secondary grounds.
> 
> A lot of USB charger style warts have even less capacitance.  It's not clear 
> to me if they have a shielded transformer (unlikely, but possible; I need to 
> take one apart some time), or if they really just don't care (there's very 
> little radiation from a wall wart, if there's no charging cable and load 
> plugged in ;-) ).  They don't usually have a CMC, or just a small one and no 
> other Y caps if they do.  (Again, not good for much, without a shunting 
> impedance to help out.)
> 
> So, after adding a few caps and chokes: your next goal is shielding, 
> surrounding the PSU core with chokes, and shunting all inputs and outputs 
> with caps to the shield.  (Shield should also be earthed, because leakage 
> current and safety.)
> 
> Tim
> 
> -- 
> Seven Transistor Labs, LLC
> Electrical Engineering Consultation and Contract Design
> Website: http://seventransistorlabs.com

"Tim Williams" <tmoranwms@gmail.com> wrote:

> "George Herold" <gherold@teachspin.com> wrote in message 
> news:558d2f39-35a3-4bf4-a1dc-b39334ce98d7@googlegroups.com...
>> Well if the ferrite didn't work you could try a shield.  I made
>> this power supply with DC-DC converters.  Nice layout and ground
>> planes, but still switching noise.  I put copper tape hats on the
>> converters and that knocked it down. 
 
> FWIW, ferrites rarely do more than 3-6dB of attenuation.  A long stack
> of them, maybe over 10dB.  The reason is, if there's no shunting
> impedance (to ground, or, more generally, to the other cable coming out
> of the box), it's an impedance divider against the capacitance-to-space
> of the cables in question.
 
> It's probably even more basic than shielding: you need to start with a 
> shunting impedance in the first place.  This is usually a 1nF Y1 ceramic
> cap between rectified mains and secondary grounds.
 
> A lot of USB charger style warts have even less capacitance.  It's not
> clear to me if they have a shielded transformer (unlikely, but possible;
> I need to take one apart some time), or if they really just don't care
> (there's very little radiation from a wall wart, if there's no charging
> cable and load plugged in ;-) ).  They don't usually have a CMC, or just
> a small one and no other Y caps if they do.  (Again, not good for much,
> without a shunting impedance to help out.)
 
> So, after adding a few caps and chokes: your next goal is shielding, 
> surrounding the PSU core with chokes, and shunting all inputs and
> outputs with caps to the shield.  (Shield should also be earthed,
> because leakage current and safety.)
 
> Tim

These attempts are futile. Find an old-style plain transformer walwart with 
a bridge rectifier or plain AC output. Or make one yourself from a 24V 
doorbell transformer.

Line noise really sucks. If you are sensitive to it, you are vulnerable to 
times when it is good, and times when it is bad. These distract you when 
you are concentrating on a different problem.

Kill the problem. Isolate yourself from these nuisances.

On Fri, 25 Aug 2017 01:54:28 GMT, Steve Wilson <no@spam.com> wrote:

>Martin Riddle <martin_ridd@verizon.net> wrote:
>
>> It's been a year or two since I listend to AM Radio, and in that time
>> theres a new Roku box and linksys router.  Well, I couldn't hear
>> anything  on the AM band when I checked a week ago. So the quest was
>> to find the culprits. Its these SMPS wall warts, they literly wipe out
>> the entire AM band, and also some chinese LED lights( 15w equiv
>> Grimaldi's ).
>> Tossing the led lights are easy, the wall warts not so.
>> I found the old DSL modem transformer wall wart and that is quiet.
>> Perusing the Innernet, I see some mention Apple supplies and the
>> Powerstream SMPS supplies are quiet too, any one here with experiance
>> with them? 
> 
>> Cheers
>
>Same problem here, except we have flourescent lights with solid-state 
>ballasts, and the line noise is something to behold. The noise blankets 
>everything up to about 10MHz. The only solution here is to take the radio 
>100 yards out in the middle of a field. There is still a lot of noise, but 
>at least you can pick up some stations. 
>
>I bought a very nice synthesized receiver to listen to the ham and 
>broadcast bands. To my dismay, I found that most of the shortwave stations 
>have shut down, since they have switched to the internet. About the only 
>ones still operating were the religious nuts trying to get donations. The 
>ham bands were down a lot also. I guess the old guys have died off, and 
>amateur radio doesn't have the same appeal as google.
>
>Electronics seems to be following the same route as the vacuum tube. But 
>there are very active local clubs into Arduinos and robotics, so there is 
>some hope for the future.


There is a lot of digital stuff around 14.070.  PSK and other varied
modes.  Of course the solar cycle is poor right now.  Evening seems
best.  
 
I like to rx the NOAA HF WEFAX stuff but they are having some problem
with sync jumping making pix pretty scrambled.


Eric WA3UYI

On Fri, 25 Aug 2017 06:25:49 -0700 (PDT), George Herold
<gherold@teachspin.com> wrote:

>On Thursday, August 24, 2017 at 9:35:20 PM UTC-4, Martin Riddle wrote:
>> It's been a year or two since I listend to AM Radio, and in that time
>> theres a new Roku box and linksys router.  Well, I couldn't hear
>> anything  on the AM band when I checked a week ago. So the quest was
>> to find the culprits. Its these SMPS wall warts, they literly wipe out
>> the entire AM band, and also some chinese LED lights( 15w equiv
>> Grimaldi's ).
>> Tossing the led lights are easy, the wall warts not so.
>> I found the old DSL modem transformer wall wart and that is quiet.
>> Perusing the Innernet, I see some mention Apple supplies and the
>> Powerstream SMPS supplies are quiet too, any one here with experiance
>> with them? 
>> 
>> Cheers
>
>Do you know if the interference is radiated or conducted?  
>(Tin foil hat (copper tape) for one, a ferrite choke thing for the 
>other?) 
>
>George H. 

I made a little loop antenna and snooped around with a portable sw rx.
Got rid of all the noisy ones, not bad now.  Of course the neighbors
have stuff too but so far not a probem.
Eric WA3UYI

"George Herold" <gherold@teachspin.com> wrote in message 
news:93599ccd-3251-4d04-93c4-a140ac54523d@googlegroups.com...
> That makes sense. I do a lot of hunt and pecking when dealing with
> interference.  Here's my fav, ferrite choking a usb line.
>
> https://www.dropbox.com/s/twhtnr6mzq7mwil/ferrite.JPG?dl=0
>
> It worked and I moved on.  :^)

The irony is, see that shielded connector and cable?  This is something that 
should be literally impossible to happen.

I wonder if there's actually a "Typhoid Mary" among appnotes where the 
connector housing is shown with a ferrite bead to ground.  USB connector 
appnotes are uniformly bad.

Tim

-- 
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Contract Design
Website: http://seventransistorlabs.com 

On Fri, 25 Aug 2017 10:56:12 -0700 (PDT), George Herold
<gherold@teachspin.com> wrote:

>On Friday, August 25, 2017 at 11:15:07 AM UTC-4, Martin Riddle wrote:
>> On Fri, 25 Aug 2017 06:25:49 -0700 (PDT), George Herold
>> <gherold@teachspin.com> wrote:
>> 
>> >On Thursday, August 24, 2017 at 9:35:20 PM UTC-4, Martin Riddle wrote:
>> >> It's been a year or two since I listend to AM Radio, and in that time
>> >> theres a new Roku box and linksys router.  Well, I couldn't hear
>> >> anything  on the AM band when I checked a week ago. So the quest was
>> >> to find the culprits. Its these SMPS wall warts, they literly wipe out
>> >> the entire AM band, and also some chinese LED lights( 15w equiv
>> >> Grimaldi's ).
>> >> Tossing the led lights are easy, the wall warts not so.
>> >> I found the old DSL modem transformer wall wart and that is quiet.
>> >> Perusing the Innernet, I see some mention Apple supplies and the
>> >> Powerstream SMPS supplies are quiet too, any one here with experiance
>> >> with them? 
>> >> 
>> >> Cheers
>> >
>> >Do you know if the interference is radiated or conducted?  
>> >(Tin foil hat (copper tape) for one, a ferrite choke thing for the 
>> >other?) 
>> >
>> >George H. 
>> 
>> Probably Conducted=> then radiated by the power lines.
>> The Favorite Fairite Bead does very little on the DC output lead.
>> 
>> I could try an Isobar power tap, to see.
>> 
>> I have a  Netgear Gbit switch that the smps Wall wart is pretty quiet
>> in comparision. As well as a Logitech speake rsmps  wallwart.
>> 
>> Cheers
>> Cheers
>
>Well if the ferrite didn't work you could try a shield.  I made 
>this power supply with DC-DC converters.  Nice layout and ground 
>planes, but still switching noise.  I put copper tape hats on the 
>converters and that knocked it down.  
>
>George H.   

I tried the Isobar and there was some improvement, signals got thru,
but there is still switching noise across the band. The transformer
wall warts work the best at the moment.

Cheers

On Friday, August 25, 2017 at 11:04:20 AM UTC-7, Tim Williams wrote:
> "George Herold" <gherold@teachspin.com> wrote in message 
> news:558d2f39-35a3-4bf4-a1dc-b39334ce98d7@googlegroups.com...
> > Well if the ferrite didn't work you could try a shield. 

> FWIW, ferrites rarely do more than 3-6dB of attenuation.  A long stack of 
> them, maybe over 10dB.  The reason is, if there's no shunting impedance (to 
> ground, or, more generally, to the other cable coming out of the box), it's 
> an impedance divider against the capacitance-to-space of the cables in 
> question.

I've seen more dramatic results than that, with the common-mode ferrite formulations
which are very lossy (it's a series resistor at RF).

On Thu, 24 Aug 2017 21:35:20 -0400, Martin Riddle
<martin_ridd@verizon.net> wrote:

>It's been a year or two since I listend to AM Radio, and in that time
>theres a new Roku box and linksys router.  Well, I couldn't hear
>anything  on the AM band when I checked a week ago. So the quest was
>to find the culprits. Its these SMPS wall warts, they literly wipe out
>the entire AM band, and also some chinese LED lights( 15w equiv
>Grimaldi's ).
>Tossing the led lights are easy, the wall warts not so.
>I found the old DSL modem transformer wall wart and that is quiet.

Welcome to my nightmare.  Ham radio operators have been dealing with
the wall wart and other devices EMI/RFI for many years.  It only gets
worse with new and more insidious sources of electrical noise arriving
every day.  For example, I recently found a garden path full of these
LED lights.  Each one has a built in switcher with little filtering
and no shielding.
<http://www.ebay.com/itm/222204398564>
Ferrite beads around the leads were a big help.

"A Ham's Guide to RFI, Ferrites, Baluns, and Audio Interfacing"
<http://audiosystemsgroup.com/RFI-Ham.pdf>
I do some computah work for the author.  I recently unloaded about 50
lbs of linear wall warts on his doorstep.  Over the years, he has
systematically replaced as many switchers with linear power supplies
as possible.  The few switchers that can't be replaced, have large
common mode toroids on both input and output leads.  Something like
these:
<http://palomar-engineers.com/rfi-kits/computer-rfi-kits>

See list of his other publications for other articles:
<http://audiosystemsgroup.com/publish.htm>
such as:
"Power Line Filters"
<http://audiosystemsgroup.com/PowerFilters.pdf>

If you're going to be chasing down sources of EMI and RFI, the best
technique is to kill the power to sections of the house at the breaker
box.  This doesn't do anything for battery backed up devices, such as
digital clocks, or deal with neighborhood sources, but otherwise works
well.  For fine tuning, I use an AM portable receiver tuned to empty
HF frequencies.  I use an Alinco DJ-X2 but any portable AM/FM/SW/AIR
receiver will work.  When I'm dealing with more exotic noise sources,
I use a spectrum analyzers.

>Perusing the Innernet, I see some mention Apple supplies and the
>Powerstream SMPS supplies are quiet too, any one here with experiance
>with them? 

I haven't done any bench tests with an LISN (line impedance
stabilization network) comparing various switchers.  Powerstream does
not actually manufacture the products they sell but buys them from
various vendors:
<https://www.powerstream.com/power2.html>
My guess(tm) is that I would expect wide variations in EMI radiation
characteristics.  The various genuine Apple power supplies that I own
seem fairly quiet for both conducted and radiated noise, but not
totally quiet.  An external filter would still be useful.  I don't
know how they compare with counterfeit and cloned Apple power supplies
or similar switchers.  



-- 
Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558