[Elecraft] KX3 12kHz audio spike

[David Gilbert]

I didn't say that RF current in a ground plane wasn't "well-behaved", 
whatever that means.  I said that it wasn't uniform, as in uniform 
density.  It's not.

73,
Dave   AB7E


On 8/7/2013 2:10 AM, Jim Brown wrote:
> On 8/6/2013 8:49 PM, David Gilbert wrote:
>> Currents most certainly do not flow uniformly in ground planes, and 
>> coupling effects can be real whenever significant gain is involved. 
>
> Actually, what happens is that a trace above an ideal "ground plane" 
> (the ground layer)  forms a transmission line, with the return current 
> flowing in the ground plane directly below he trace -- UNLESS the 
> ground plane below the trace is broken, for example, by the circuit 
> board layout guy realizing he left something off the main layer, and 
> putting on the ground layer instead. In which case there is no longer 
> a transmission line, the return current flows wherever it can. 
> inductance is added to the path, which causes magnetic coupling to 
> other circuits, and it forms an antenna, so it can radiate, into other 
> circuitry, or outside the box, or both.
>
> So the RF current in a ground plane is VERY well behaved and 
> predictable. The problems arise when the PC layout guy doesn't 
> understand the function of the ground plane, and that it CANNOT be 
> interrupted without consequences. Like zipper noise on tuning in the K3.
>
> 73, Jim K9YC
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