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Re: Topband: T Top Verticals and yagis

To: topband@contesting.com
Subject: Re: Topband: T Top Verticals and yagis
From: Jim Brown <jim@audiosystemsgroup.com>
Reply-to: jim@audiosystemsgroup.com
Date: Sun, 1 Mar 2020 14:50:41 -0800
List-post: <mailto:topband@contesting.com>
On 2/27/2020 8:23 PM, donovanf@starpower.net wrote:
Your conclusions based on your modelling are completely consistent
with my practical experience and modelling.

My experience with building what I model or modeling what I've built has been that if I've built the model to accurately represent ALL of reality, the model correlates well with how the antenna works. This applies equally to matching networks and other circuitry.

In my professional life, I did pretty complex models for the large sound systems I designed, often including acoustic models of large public spaces where they would be installed. The sound system models were an order of magnitude more complex than most antenna systems, and the acoustic models an order of magnitude more complex than the sound system model. Again, results were as good (or as bad) as the data that I put into the model.

And in my third year of EE, '61-'62) my coop job was crunching numbers for Pete Johnson for his designs of multi-tower AM broadcast arrays. Pete and Carl Smith (Cleveland Radio and Electronics Institute) wrote the FCC technical Rules for the AM band after WWII. Four of us sat around a conference room table with slide rules and math tables filling very wide paper spreadsheets with 25-30 columns of numbers, each column being the result of one step in the calc. The calc was repeated for every 5 degrees of azimuth and 5 degrees of elevation. It could take days to finish a pattern. Pete would study the results, change a variable or two (magnitude and phase of current in elements, move the towers around, etc) and we'd do it all again. In 2020, the same model could be computed in the laptop on most of our desks in a few minutes.

73, Jim K9YC

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