[KLQRP] NVIS antenna tweaked

[Bob Kellogg]

Gentlemen,

Derek and John Paul asked a reasonable question:  Would the antenna 
perform better if a standard 30' TV mast were used?  I modeled it using 
EZNEC and found that it would not. 

This piqued my curiosity so I modeled the antenna at several heights, 
and much to my surprise (although it's logical on second thought) the 
best height for the NVIS as designed is 13.5 feet!  Modeled gain is 
roughly 9 to 11.5 db, depending on soil conditions, on 80M, and 7.25 to 
7.5 db on 40 meters. 

The new height prompted some wire length tweaking, so the new lengths 
are 66.5 feet and 32.33 feet.

With the center of the antenna closer to the ground the "vee" is 
straightened out a little, focusing more of the signal straight up, thus 
the higher gain.  (I'm measuring gain straight up)

My test antenna needs some revision to meet the modeled dimensions, and 
I'm going to make them as soon as I get a chance.  Then we'll be able to 
check actual contacts.  Perhaps the straight up signal won't scatter as 
far as the flatter one, however this will probably depend more on 
atmospheric conditions than anything else.....  To be continued.

-- 
Best Wishes,

Bob Kellogg
Greensboro, NC
Prolably, not nececelery - Benny Hill