[Elecraft] Switching power supplies...yet another comment

[Jim Brown]

On Sat, 17 Jul 2010 08:32:24 -0700, Vic K2VCO wrote:

>I think a lot has to do with the antenna, and how it's connected to the rig. If you are 
>using a balanced antenna, properly fed with coax and a balun or two-wire line with a 
>well-balanced tuner, it's unlikely that you will have a problem. If you have a wire stuck 
>in the coax connector of your rig, then you almost certainly will. Other setups will be in 
>between.

>A dipole fed with coax with no balun will certainly be vulnerable to picking up noise on 
>the outside of the shield. Noise currents flowing on the shield will then be connected 
>directly to the antenna at the feedpoint! If the coax runs near power wiring which is 
>connected to a switching supply (or computer, etc.) then you are asking for trouble.

Exactly right. What matters is not proximity of the power supply to the rig, but the power 
supply to the antennas!  

I have some switchers in my shack and in my house. Most of my antennas are high and away from 
those noise sources, but two antennas (160M and 2M) are quite close to the shack. I have 
ferrite common mode chokes on ALL of those switchers, and I had to get VERY serious with the 
two cheap switchers in my shack that float-charge my batteries to kill the noise on 160M and 
2M. They're now quiet, but they didn't come that way. :) 

73, Jim K9YC