[TowerTalk] re Radials
aa4lr at arrl.net
Fri Jun 16 20:55:30 EDT 2006
On Jun 16, 2006, at 10:11 AM, Bill Turner wrote:
> Yes, I know verticals have a lower radiation angle, but on 160/80/40
> most signals arrive at high angles anyway. On the higher frequencies
> a vertical would be more practical, but there most folks use beams.
Horizontal antennas, like dipoles, make great antennas, but they are
affected by proximity to the ground. They have to be at least 1/4
wave above ground before the radiation pattern is anything but
straight up. Dipoles don't start to have a distinctive bi-directional
pattern until they are about 1/2 wave or higher.
For 160, this means a couple of 40m or 80m high supports. That's 133
to 266 feet high! For 80m, that's at 66 to 133 feet high. Few hams
have antenna supports this high.
For 40m and higher, many hams have the resources to mount horizontal
antennas sufficiently high for them to be effective antennas, even
for DX. But for 160m and 80m, finding sufficiently high supports is
There's also evidence that suggests that verticals may be more
effective low-band antennas. W8JI relates that his 300 foot high
dipole for 160m is only more effective than his verticals under very
special propagation conditions. For more than 90% of operating time,
the verticals work better.
Bottom line, for the typical ham, compromise verticals are more
effective DX antennas than compromise dipoles on 160 and 80m.
Bill Coleman, AA4LR, PP-ASEL Mail: aa4lr at arrl.net
Quote: "Not within a thousand years will man ever fly!"
-- Wilbur Wright, 1901
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