[BC] Null Distortion (WAS: Westinghouse at NAB)

[PeterH5322]

>What happens with some DA's is a phase reversal zone and the reversal
>azimuth is slightly skewed in the sidebands. This will be in an area
>where one side of the null is + carrier and the other side is - carrier.

Most AM DA programs report resultant field as a magnitude (absolute 
value), only, at a given bearing.

My ca. 1964-1965 AM DA design computed both the magnitude and the phase.

Both are available from the same computation, in some cases.

In my case, I was using FORTRAN II, which has no COMPLEX data type, and 
for which I was separately managing the X and Y components of various 
vectors.

When I finally computed the field, I could also compute the phase, and I 
elected to do so, and to display it, along with the field.

These "phase reversals", and, indeed, a slowly or rapidly changing phase, 
within a minima or a null, are, I believe, responsible for "null 
distortion".

So, rapidly changing phase (including phase reversal) can occur within a 
minima (slowly changing magnitude), or a true null (rapidly changing 
magnitude), while slowly changing phase (including phase reversal) can 
occur within a true null (rapidly changing magnitude), or a minima 
(slowly changing magnitude).

The combination of rapidly changing magnitude and rapidly changing phase 
is, I believe, largely responsible for "null distortion".

Or, so was my conclusion in 1965.