With all the discussion of falling 2000' towers, I got curious, just in
case someone was planning to pick all the pieces and put one in the back
yard.
A 40-meter vertical dipole atop a 2000' tower will have a gain of abut
7.55 dBi with lobes at 1, 3, 5, etc. degrees.
Do not place your 20 meter Yagi at 2000'. Try somewhere between 1740 and
1860' feet instead. Here is a little chart of models every 40' down from
2000 for a 3-element Yagi with a free space gain of about 8.1 dBi:
Height Gain Take-off angle
2000 12.65 23 degrees
1900 13.65 10
1860 13.77 7
1820 13.87 6
1780 13.89 5
1740 13.97 4
1700 13.84 3
Pick your angle and your gain, and only buy as much scrap tower as needed.
-73-
LB, W4RNL
--
FAQ on WWW: http://www.contesting.com/towertalkfaq.html
Submissions: towertalk@contesting.com
Administrative requests: towertalk-REQUEST@contesting.com
Problems: owner-towertalk@contesting.com
|