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Re: [TowerTalk] Building Antennas

To: "AD5VJ Bob" <>, <>
Subject: Re: [TowerTalk] Building Antennas
From: Jim Lux <>
Date: Sun, 15 Jan 2006 19:52:58 -0800
List-post: <>
At 04:03 PM 1/15/2006, AD5VJ  Bob wrote:
>I have printed all of your replies and want to thank you
>all for taking your time to answer my question.
>Now I am in the mode of researching all the answers.
>Thanks one and all.
>What spurred this desire to do my own was I downloaded an
>old amateur book from 1959 and was reading the antenna
>One thing that hit me between the eyes was that although
>computers and rigs have changed drastically.
>Antennas are the same. Interested there have been no
>advances in antennas, oh sure there have been some  who
>say theirs is better different, ect. But when you get
>right down to it the "magic" has not changed at all.

Lots of changes in antenna technology.  Not in the metal or construction 
technique (although there's a lot of nice composites available today), but 
in the design and analysis.  Back in the 50s, antenna design was very 
empirical (try it and see if it works).  Yagis were often modifications of 
the NBS standard designs.

It was very difficult to do tradeoffs between SWR bandwidth, gain, etc. in 
any sort of systematic way.  There's so many variables to adjust, and the 
interactions are non trivial. A fairly vanilla 3 element beam has 5 basic 
independent variables (3 element lengths, two spacings) and if you start 
adding in taper schedules and matching networks, it gets real wild.

Today, you've got extremely powerful modeling tools that will, if properly 
used, let you predict the performance of a design to tenths of a 
dB.  Optimizing modern beam designs (such as interleaved multiband yagis) 
would be a real chore without modeling tools.

The other technology in antennas that has made a real difference (aside 
from truly radical new technologies like motorized elements, e.g. SteppIR) 
is that fast automatic antenna tuners have allowed people to design 
antennas optimized for radiation pattern, and not worry so much about SWR 

However, even with all the new stuff for antennas, the "implementation 
skills" haven't changed.  It's still just cutting metal, drilling holes, etc.
And that's fairly satisfying.. no trying to solder microscopic SMD devices, 

>   73 fer nw,
>Bob AD5VJ

Jim, W6RMK


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