Topband: one-way propagation

[Jim Brown]

Tom,

I don't think anyone takes issue with the concept of propagated noise 
raising the noise level on one side of the QSO while the other side is 
still quiet. Anyone who looks for it will see it if their QTH is 
relatively quiet, and I regularly see the 10-15 dB variation you've 
often cited.

But what Carl has cited here was apparently serious scientific 
observation that showed a difference of nearly 10dB. That's a lot, and 
if they were measuring field strength and not signal to noise ratio, it 
means that there's something going on that we haven't figured out yet.  
That observation is one important part of the scientific process. 
Another part is starting from that observation and trying to understand 
why.  Many times in my life I've observed something through careful 
observation, then worked to try to understand it.

Our concept of reciprocity applies to linear systems that are 
time-invariant, and, just as with a wired network of passive components, 
the source and termination impedances are part of the network.  With 
propagation, it's generally well known that the signal path can mess 
with polarization, and it's not hard to believe that that effect could 
be different in different directions.

73, Jim K9YC

On 12/4/2012 2:09 PM, Tom W8JI wrote:
>>
>
> I can't recall anyone who has made a study of this citing that as a 
> reason for non-reciprocity, and Carl's recent post about a broadcast 
> study said the effect someone reported seeing was only on a west-east 
> path and no one knew why.  The reasons theorists have cited have only 
> to due with gyrorotation.
>
> I'm not saying you are wrong, but what have they missed to not bring 
> the issues you highlight up? In all of the conditions you mention, 
> what specific mechanism causes a path to be non-reciprocal at any 
> instant of time?
>
> I know why things like lossy networks can be non-reciprocal in 
> impedance, but what is the mechanism at work?