[TowerTalk] 20m monoband Yagi height

[David Gilbert]

The answer to your question isn't simple, but HFTA will give you good 
insight into the problem.

50 feet will give you decent radiation at almost all elevation angles 
except for the very low ones (less than 5 to 8 degrees), but even from 
Florida to Europe those low angles are important.  70 feet will give you 
about 3 more dB at 5 degrees takeoff, but give you a deep notch at 31 
degrees.  100 feet will give you about 6.5 db more than at 50 feet, but 
will give you a deep notch at 21 degrees.

It is very easy to do this in HFTA.  I'll send you a couple of plots for 
illustration.  The vertical purple bars represent the weighted 
importance of the various angles for the listed destination from Florida 
based upon the ARRL calculations for the distribution of the VOACAP 
variable TANGLE (optimum takeoff angle) ... which probably shouldn't be 
taken too literally since of the roughly 20 variables available for 
analysis in VOACAP, its author has stated that TANGLE probably has the 
least accuracy.  Still, as far as I know it's the probably the best we 
have at this point.

73,
Dave   AB7E






On 7/14/2020 9:24 AM, Robert Gerace wrote:
> Please forgive my inability to figure out how to search archives by subject as I have to imagine this is a common question.
>
> Understanding the best answer is “as high as possible” and the second best answer is at least one wavelength...
>
> I wanted to ask about some real world experience between 50’ and 66-70’...
>
> Specifically: given the same antenna, same QTH, same general point in the solar cycle...
>
> Has anyone had a 20m monoband, trapless beam at ~50’, then raised it to ~70’ and seen enough consistent improvement to justify the effort?
>
> Background:
>
> Given my QTH I have about 55’ to tilt my (in process of permitting) tower. If I want to go higher I’m clear to 70 easy. However it will require telescoping (e.g. lower to 55, then tilt) to be able to service from the ground — a requirement for me.)
>
> The cost difference is very substantial all the way around: purchase, shipping, footing, installation).
>
> So I’m wondering if it’s worth all the time and trouble to get an extra 15-20 feet?
>
> Background: I’d like a big signal, would like to have at least a 50-75% chance to bust most pileups... even if it takes patience...but I’m a casual DXer who after 44 years is getting serious about 20m CW DXCC.
>
> I’m not trying to be the guy who is first through the pileup or even places in a DX contest... but I’m tired of being the guy who can only reach for low hanging fruit. I want to work some more dopamine inducing DX and maybe turn in something more than average on contests.
>
> I live in NE FL, a mile from the beach, on very sandy soils, and have oak trees at 45’.
>
> Any insight appreciated.
>
> Thanks es 73
> Bob
> KD4Q
>
> Sent from my iPhone
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