At 02:25 AM 3/4/99 -0500, Guy Olinger, K2AV wrote:
>I would want to see a terrain analysis, e.g., the effect of your terrain on
>the idealized pattern of your 40 meter antenna.
>But in general, the 70 foot height suppresses high angle radiation, and has
>a single pronounced lobe at the low angles. Another poster commented on a
>stronger signal at 95 feet later in the opening.
>Using my terrain toward NE, I get the following with a 2 el yagi at various
>heights using TA.
>height main lobe high lobe
>66 11.8 Dbi 29-32 deg none
>72 11.9 Dbi 26-30 deg none
>78 12.1 Dbi 23-27 deg -3.8 Dbi 77 deg
>84 12.3 Dbi 23-26 deg 0.3 Dbi 77 deg
>90 12.4 Dbi 22-25 deg 2.9 Dbi 75 deg
Just a couple of comments ...
The 75-77 degree lobe is essentially meaningless for ionospheric
propagation, except maybe some specialized modes for near-in QSOs (NVIS).
The main lobe data need to be compared with arrival angle data from the
areas of interest. Use the revised arrival angle data files on the ARRL
Web Page rather than the ones shipped with the Antenna Book -- N6BV revised
them late last year to remove some potential systematic bias.
The match between European arrival angles and the pattern of my 2-element
40m yagi at 108 feet is just about perfect. If anything, I'd expect lower
angles in W9-land. Another argument for going higher rather than lower.
73, Pete Smith N4ZR
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