[Elecraft] Noise from KAT500?

[Bill Johnson]

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-bounces at mailman.qth.net <elecraft-bounces at mailman.qth.net> On Behalf Of Jim Brown
Sent: Saturday, December 2, 2023 8:25 PM
To: elecraft at 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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