[Aavso-sid-list] Too close, too far?

[Peter Wilhelm Schnoor]

Hi Dusty,

Assuming that "SID-Detection" was meant... (*_*)

Dusty wrote:
> ...
> Q.  How close is too close to avoid the VLF ground wave?

A.: if you cannot see the typical differences between night
     and day time propagation.

> Q.  How far is too far not to receive the reflected VLF signal?

A.: if you are not able to detect the signal strengths or
     phases reliably around the clock.

It's nearly impossible to specify miles or km for both cases. It 
depends on transmitting power, transmitting antennas, both 
latitudes, propagation path, your antenna, environment and 
intrinsic noise figures, etc.

If ground waves seem to strong for the detection of sky wave 
fluctuations you could try nulling out the ground wave 
propagation by means of loop/ferrite antennas. This would 
seperate it from sky waves which are coming in at higher angles. 
It was a well-established practice by researchers some 40 years 
ago here in Europe.

Any protests?

Peter