[Elecraft] (OT) - Unplanned Discovery

[Josh]

Noise can absolutely change with load. At light load the SMPS may enter a pulse skipping mode. Some keep pulse width constant and vary switching frequency with load to effectively change duty cycle. Most (all?) will continuously modulate the switching frequency over a small range to spread out the pulse energy. This makes it much easier to come in under required limits, but also by the time you're looking at harmonics up in our bands it's a big smudge of noise. 

73,
Josh W6XU

Sent from my mobile device

> On Nov 20, 2017, at 12:58 PM, Doug Smith <doug at w7kf.com> wrote:
> 
> I have often wondered if the noise from a switching power supply would vary in intensity or other characteristics as the load changes.  For example, during transmitting.  In a single transmitter environment the user would probably not notice but in a multi-transmitter or SO2R station one just might.  
> 
> Changes in noise floor might not always be “phase noise” from the other transmitter — could it be different emissions from a switching power supply under full load?
> 
> 73,
> Doug, W7KF
> http://www.w7kf.com <http://www.w7kf.com/>
> 
> 
>> On Nov 19, 2017, at 6:42 PM, stan levandowski <sjl219 at optonline.net> wrote:
>> 
>> Yeah, me too.  I bought it because I thought it would be "super clean" and really small.  But its contribution to my problem was pretty much unarguable:  Plug it in and I hear noise.  Unplug it and I don't hear noise.  The instructions that came with it specifically stated that the Kx33 should be placed the full length of the DC plug/cord away from the transceiver.  I did that but it didn't work for me.  I tried different outlets around the house too.  I put chokes on it.  No joy.
>>