Bill,
At the risk of going a bit off topic from Elecraft here-- I use a power
distribution block, and run 12 volts to every device I can reach from a
known good supply.
For the items I can get to with that 12V I go to the local thrift
stores, and look at the used wall wart power supplies. I buy the heavy
ones...
I then test them at home, both loaded and unloaded for voltage and RFI.
If good I use them, if bad, I recycle them. Most used PS at the thrift
stores are cheap, and the heavy ones are usually transformer based, and
RF quiet..
73, and thanks,
Dave (NK7Z)
https://www.nk7z.net
ARRL Volunteer Examiner
ARRL Technical Specialist, RFI
ARRL Asst. Director, NW Division, Technical Resources
On 12/2/23 21:19, Bill Johnson wrote:
It gets worse with all the new gadgets and LED lighting. I just installed new
plant lights, LEDs, and the racket from the wall warts is terrible. I shut
them off when operating, or not interested in lighting up the plants. Terrible
view of the noise on K4 graphic display.
Bill
K9YEQ
-----Original Message-----
From: elecraft-boun...@mailman.qth.net <elecraft-boun...@mailman.qth.net> On
Behalf Of Jim Brown
Sent: Saturday, December 2, 2023 8:25 PM
To: elecraft@mailman.qth.net
Subject: Re: [Elecraft] Noise from KAT500?
On 12/2/2023 5:48 PM, W2HX wrote:
I then replaced the wall-wart power supply with a 12V battery. And
this is what I saw for BOTH bypass and inline. Clearly the problem.
https://w2hx.com/x/Elecraft/KAT500/Noise-Issue/KAT500-battery.png
using a battery, the noise is about -80 dBm. Using the wall-wart, in
some cases the noise is as high as -60 dBm
My task now is to either leave it on battery or preferably, find a low noise PS.
99.9% of stuff that plugs into the wall has a Switch-mode power supply, most of
which are varying degrees of noisy. They were mandated to save energy about 20
years ago, but thanks to small government, the FCC has no money to enforce
their Rules that they be quiet. So they aren't.
A typical home has several dozen of them, either in the form of wall warts and
line lumps or built into equipment and appliances. Rather than buying bigger
and better anything for our station, our time and money is far better spent
identifying and replacing as many as possible of these nasty noise sources.
There's a tutorial on my website, k9yc.com/publish.htm about how to find and
replace them. All of the 12V gear in my shack runs on two big batteries that
are float charged by re-purposed Thinkpad power supplies using Genasun charge
regulators. A 100Ah LiFePO4 runs the rigs, a 100Ah Sealed Lead Acid runs the
rest of the stuff.
73, Jim K9YC
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