Simply put, antennas at a given height have MULTIPLE lobes at different wave
angles of varying gain over flat ground over average soil. If you have
anything other than flat ground and especially if you have complex terrain or
are on the side of a hill or adjacent to water, your antenna at 1/4 or 3/8 wave
height above ground might have useful high angle lobes and some unexpected low
angle lobes despite the low height. This is why it is important to model your
antenna over actual terrain – and the ground conductivity with fertile ground
vs. sandy soil or ledge also makes a difference and can be quite helpful.
I live in Western CT and on 160 I use a wire Inverted L with a top height of
85’ with the rest of the wire horizontal and 3 elevated 1/4 wave radials no
greater than 10’ above ground. It is a proverbial “cloud warmer” and yet I
have worked 200+ countries and 33 zones with it along with a handful of JA’s on
160. And I haven’t tried very hard. And the antenna is on ledge and deep
forest “soil” on the top of a hill with awful ground conductivity. The hill
helps but it is primarily a high angle antenna – no matter – it works fairly
well most of the time. It would work better if it was all vertical but that
is not possible at my qth. If I listened to the “doom and gloom” of some
opinions about height above ground I wouldn’t have bothered to put it up or
even tune the band.
Bottom line:
MODEL several proposed antennas over your specific terrain at your qth. You
may discover advantages at a given height that are counter-intuitive, and then
put it up and get on the air. Often your antenna will be far more useful than
you could imagine despite what others think.
BTW, most antennas are louder over some path at different times depending on
the height (or lack of it). My 3 L wire beam @ 50’ on 40 is VERY loud to EU
for about 2 hours early in the opening; as loud as a yagi would be at the same
time at a high height. The difference is that after those two hours, the Yagi
would be 10 db – 2 s-units louder from the combination of antenna gain PLUS
being at a higher and more optimum height for the given arrival wave angles
from EU. The wire beam has its usefulness even though a quality Yagi at a high
height would be better. What would be best is to have both – each for its
advantages at different times.
Actual results trump theory. If it works then use it. If it works well then
enjoy it regardless of what anyone else thinks about it!
63’ vs. 67’ on 40 is not even worth considering if it looks close enough after
modeling it over your terrain. Go with whatever is easiest for you.
73
Bob KQ2M
From: Peter Voelpel
Sent: Thursday, January 17, 2019 3:37 PM
To: 'Tower Talk'
Subject: Re: [TowerTalk] Half Wave?
A 1/4 wave length height IS exactly a cloud warmer.
At least 3/8 wave length height is necessary for a lower take off angle.
73
Peter
-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces@contesting.com] On Behalf Of Keith
Dutson
Sent: Donnerstag, 17. Januar 2019 21:27
To: Tower Talk
Subject: Re: [TowerTalk] Half Wave?
My experience is that 1/4 wavelength is okay to avoid a cloud warmer.
However, higher is always better for DX, aka lower take-off angle.
73, Keith NM5G
-----Original Message-----
From: TowerTalk <towertalk-bounces@contesting.com> On Behalf Of Warren Wolff
via TowerTalk
Sent: Thursday, January 17, 2019 11:47 AM
To: towertalk@contesting.com
Subject: [TowerTalk] Half Wave?
Greetings: My understanding is that a yagi should be at least 1/2wave
above ground to avoid warming the clouds. So, considering that thought,
how much does an antennasuffer if such antenna is 63 feet up instead of 67
feetfor 40 meters over VERY rocky "soil"? Thanks, Warren; W7WY
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