[TowerTalk] Stacking Distances

[Pete Smith]

At 08:50 AM 5/22/03 -0400, Paul Christensen, Esq. wrote:
>Question:  Is 5/8-wave used as a compromise spread in that the difference
>between 1 w.l. and 5/8 w.l. is relatively small but closer than 5/8 w.l.
>produces quickly diminishing forward gain?  Or, is there a benefit of 5/8
>w.l. that minimizes an unwanted lobe?


Here's a table of gain, take-off angle and F/B versus stacking distance for 
6-element OWA 20M yagis, as computed by NEC-2.  In all cases, I used the 
1X/2X rule -- a classic choice for cancellation of the second forward 
lobe.  So If Ht = 40 feet, then the stack is at 40/80 feet, and so 
on.  It's fairly intriguing that the best combination of F/R and gain 
happens at 90/180.  Presumably this setup is not much used because the 
take-off angle is too low for Europe (at least from the East Coast).  I 
haven't looked at how these characteristics vary across the band at the 
various spacings, but I wouldn't be surprised if the "sharpness" of the max 
gain and max SWR points within the band varied considerably.

Freq   Ht     R    X     SWR Gain  TOA F/R
14.200 40   26.82 1.64 1.867 16.34 14 20.74
14.200 45   26.75 2.04 1.873 16.73 12 20.01
14.200 50   27.71 2.40 1.810 16.99 11 18.76
14.200 55   28.84 0.91 1.735 17.25 10 16.32
14.200 60   28.02 -0.54 1.785 17.53 9 17.10
14.200 65   26.98 -0.87 1.854 17.72 9 18.37
14.200 70   26.28 -0.73 1.903 17.81 8 19.33
14.200 75   25.86 -0.44 1.934 17.81 8 19.45
14.200 80   25.65 -0.12 1.949 17.82 7 17.76
14.200 85   25.66 0.18 1.949 17.83 7 18.99
14.200 90   25.76 0.22 1.941 17.81 6 20.74

73, Pete N4ZR
The World HF Contest Station Database was updated 9 May 03.
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