Low RFI wall warts?

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  • Updated 9 months ago
I'm slowly working down the noise floor that is bothersome in the lower bands.  I've made some decent progress with robust grounding of all my equipment (good for a dB or so) and putting chokes in both ends of my PC-6500 Ethernet cable (a BIG help, it was NOISY).  Now I'm told that my many ham shack wall warts (most for USB ports) may be a noise source.  While they are small, they are often switching power supplies and potentially noisy.  I'd like to replace them. 
Does anyone have recommendations for a quiet (linear?) 5V power supply with multiple USB ports?
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Steve - K6SRS

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Posted 9 months ago

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Stephen Hawkins NG0G

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Me too.  I am discovering noise sources everywhere.  Among the worst were two brand new Chamberlin garage door openers.   I need to find a inexpensive source for those snap on chokes, as with two, eight port switches I have a lot of cat5.  
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Larry - W8LLL

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https://www.mouser.com/

These are Mouser part numbers for 31 mix snap on chokes, other 

mixes available as well. Pricing improves as your quantity 

purchaced goes up.

623-0431167281  Fits  LMR-240 10.15 mm ID
623-0431164181  Fits  LMR-400 13.05 mm ID
623-0431173551  Fits  LMR-600 18.8 mm ID
(Edited)
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John - K3MA

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Good source of chokes and other grounding stuff here.
http://www.kf7p.com/KF7P/Products.html

John K3MA
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Michael Walker, Employee

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This document is my bible regarding chokes. I highly recommend every one take a look at it. I've spent hundreds on mix 43 chokes and have been very pleased with the results and how I can hear so much better. http://www.yccc.org/Articles/W1HIS/Co...
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Alan W4FBI

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Michael - are you sure that is the correct link? Couldn't find any choke article...thx
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Larry Williamson

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I think this may have been what he meant for the link.http://www.pi4vli.nl/download/Bijlage_Deltaloep_April_2016_RFI_Ham.pdf
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Alan W4FBI

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Got it. thx Larry...
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Michael Walker, Employee

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Paul Christensen, W9AC, Elmer

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>"Me too.  I am discovering noise sources everywhere.  Among the worst were two brand new Chamberlin garage door openers."

The latest Chamberlain models are strong RFI/EMI radiators. At my home QTH, I use open feeders located about 20 ft. away from the opener.

The attached photo shows the fix -- as ridiculous as it looks.  To get ample turns, wires were extended and include the safety photo-sensor wires.    A single #31 toroid is used with several choking turns -- but that wasn't enough.  Also seen in the photo are Sprague low-ESR "Orange Drop" bypass caps.  That took care of it. 

It's insane the extent to which we need to quiet down commercially-made digital devices these days.  Hunting down RFI from new home devices and appliances is always a constant battle here. 

Wall warts: Thank God Jameco still sells a large selection of linear wall warts.  They have both regulated and non-regulated types.  I've ordered many over the years as replacements to the junk that's normally supplied with digital devices. 

Paul, W9AC


   
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Steve - K6SRS

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Ahh.  You are correct.  S0 is what shows using my ICOM 7300.  Switching to the 6500 does indeed get me an S3 without an antenna or into a dummy load.  Interesting. 
Not grasping the logic behind that.
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Bill -VA3WTB

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In a radio there is always  RF around. In SSDR the receiver gets RF from the bins in the bandpass, so even without an antenna the bins are still active and produce a tiny amount of RF.  This is a very simple way of saying it.
If you look around there are lots of discussion on this and Steve at Flex explains this in better detail. If your so interested.
(Edited)
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KY6LA - Howard, Elmer

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The bins DO NOT GENERATE RF   they are a mathematical construct to explain how SDR's receive a signal ;

Background RF is always present - unless you have a perfect Faraday cage around the radio.    The 7300 does Not display the true environment but only a relative and basically meaningless approximation of the signal to background   The Flex displays what it actually hears

https://d2r1vs3d9006ap.cloudfront.net/s3_images/935425/S-MeterGraph.jpg?1375457399 

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Larry Williamson

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Can you let us know what the noise level was before and after this fix? This is one thing I have never done (unplug it and see if it make any difference). One thing I have found is the shack laptop dell power supply and very noisy but unplugging it doesn't seem to have any effect on the radios noise level.
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Steve - K6SRS

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According to the graph I'm between rural and quiet rural, about correct for my location.  So the QRM is just what it is these days?  Too bad.  I remember good old days when quiet was quiet.

Reading S3 into a dummy load clearly is not anything like an accurate measurement of what is really coming in the antenna.  Seem like my 7300, although less smart, provides a more accurate representation of the antenna noise.
 
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Mark - WS7M

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I have personally simply tried to remove these by replacing them with either 12V or 5V products that I could power from my main 12V or a linear 5V supply.
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Steve - K6SRS

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Recommendation for a 5v linear power supply?
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Ted VE3TRQ

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Looks nice, but not a linear PSU - still a switcher, which is OK if it is proven to be quiet. Of course that's often a crapshoot.
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Clay N9IO

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Earlier in this thread Paul W9AC said that Jameco has a large assortment of linear wall wart supplies available.
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Steve - K6SRS

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Have been looking.  Hard to tell which ones are linear.
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Paul

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If the specification says the supply can operate on a wide mains input voltage range without manual adjustment, then it is almost certainly a switch-mode type. Those which only operate over a nominal range or can be manually adjusted via the primary are more likely to be linear. Unfortunately some manufacturers use all the buzz words they can think of (including linear/swiched in the same sentence!) which makes it harder to determine if it actually is linear or not.

One possible source is the audio industry. They do offer linear, low noise supplies but they are not a cheap as they should be. This is a reasonably priced example:

https://www.audiophonics.fr/en/hi-fi-...

Hope this helps. 73, Paul.
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Clay N9IO

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If you can find them at a decent price a nice 12v to 5v dc-dc converter module is made by TDK Lambda.


Also, pending on your applications current requirement you could always resort to a 5volt regulator with an output filter cap. TO-3 case regulator will handle 1 1/2 amps at 5vdc feed it from your 12 volt supply.

aka 7805 regulator.
Just add solder.
(Edited)
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Stephen Hawkins NG0G

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I have replaced all my wallwarts with a long cable intesperesed with toroids, and lot of little short pigtails, all ending in the same plug the walwarts had.  The cable was powered by an Astron RS-20A, old fashion, non-switching, plain vanilla, QUIET, power supply.  A true pain in the butt soldering a heavier gauge wire on to all those plugs meant for little tiny wires.   I should have purchased stock in companies that make solder, and shrink tubing.  My Weller soldering station actually let out an audible sigh when I was done.  NSFW  A lot of swearing was involved.
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Steve - K6SRS

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All the USB chargers seem to be current controlled or limited to numbers like 1 amp or 2.1 amps.  I'm wondering - is there is a risk to different devices when all the outlets hooked to a 20 amp source?  Don't want to fry anything.
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Bill -VA3WTB

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You really only need to think about the voltages that some devices need. The amps is just what all devices draw all together.
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Craig Williams

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I think my friend Steve needs to bring his Flex to my house for a few years and I will test the problem. He can use my 3000.