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.
>
>BTW:
>What spurred this desire to do my own was I downloaded an
>old amateur book from 1959 and was reading the antenna
>section.
>
>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
bandwidth.
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,
etc.
> 73 fer nw,
>Bob AD5VJ
Jim, W6RMK
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|