[Elecraft] Noise from KAT500?

[David Gilbert]

The ones I measured just a couple of months ago were way too small and 
light to have a transformer in them, and they were horrible.  In any 
case, I recommend that anyone using a wall wart for other than its 
intended equipment (or any standalone new one) be sure to check it for 
both noise and no load voltage regulation.  It's quick and easy to do 
and could save a lot of headaches.

73,
Dave  AB7E



On 12/2/2023 9:09 PM, Victor Rosenthal 4X6GP wrote:
> This is usually true of the linear type of wall-wart, which is the 
> quiet kind! They generally are composed of just a transformer, 
> rectifier, and capacitor.They are almost extinct these days, but I 
> look for discarded ones for use with equipment for which it is safe to 
> use an unregulated power source.
> The switching types mostly are well-regulated, but of course they are 
> often noisy.
>
> 73,
> Victor, 4X6GP
> Rehovot, Israel
> formerly K2VCO
> CWops no. 5
> http://www.qsl.net/k2vco/
>
> On 03/12/2023 5:33, David Gilbert wrote:
>>
>> Most of them have almost no reliable voltage regulation either. They 
>> are typically designed for a certain load, and if they don't see that 
>> load the voltage is much higher than rated.  I've tested dozens of 
>> these things (I tend not to throw anything away) and it's fairly 
>> typical that a 12 volt rated wall wart power supply presents 16 to 18 
>> volts (or higher) no load.  That can be death to a piece of 12 volt 
>> gear that doesn't draw much current.
>>
>> Dave   AB7E
>>
>>
>>
>> On 12/2/2023 8:25 PM, Jim Brown wrote:
>>>
>>> 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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