[HIham] inter-island propagation (low solar cycle)

[wmunro at lava.net]

To all:

A valuable chart which sheds much light on short-distance HF  
propagation (such as across the state of Hawaii) appears on page 92 of  
Radio Antenna Engineering by Edmund Laport.

This old but wonderful book (long out-of-print but still frequently  
referenced) is available as a free download from www.lulu.com (a  
"print-on-demand" outfit) or a soft-bound copy including postage is  
available for under $20.  Such a deal hi hi. The copyright was  
determined to have expired without renewal, so this is NOT a bootleg  
operation.

This chart shows mathematically necessary radiation angles for SHORTER  
distances than the usual antenna books. It does have limitations such  
as it considers an RF emission as single-ray (for simplicity) and it  
doesn't consider the over-water effects that we experience.  And to  
work, there has to be E and F layers at some height as shown on the  
chart.  Note, therefore it is not really frequency dependent (however  
depending on availability of ionospheric layer(s) at any given  
frequency).

But it shows to some relative precision the range of radiation angles  
best suited for our kind of distances across the state.

It shows me that if the band is open end-to-end across the state (and  
open between Hawaii and Oahu), but Oahu cannot even hear Kauai, then  
Kauai needs more high angle radiation, because the "E" layer HAS to  
cover the entire state (unlikely there is a "hole" at a shorter  
distance).

I can provide copies for anyone interested.

73,

Warren  KH6WM