[Elecraft] Noise from KAT500?

[Jim Brown]

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