Re: antennas

Rich Grise <rich@xxxxxxxxxxx> hath wroth:

In a broad sense, anything that gets built had to have been designed.

Choke, cough, sputter, etc... I need a rant. I've done cleanup jobs
on products that never saw the benefits of a calculation. Many were
reverse engineered or cloned, with only a minimum understanding of the
original design[1]. The rush to market has created some truly amazing
implementations that border on butchery. In the broad sense, I agree
that most things eventually are designed, calculated, re-designed,
re-calculated, optimized, cost reduced, cost reduced some more,
butchered, and delivered. Many products are a basically good idea,
badly implemented, and held together by a mess of band aids. Touch
anything, and the house of cards falls over. Fortunately, it was
fixing such butchery that kept me in business for a long time.

My business card still reads "If this stuff worked, you wouldn't need
me".

Since we're talking about antennas, has anyone ever tried to model the
typical Radio Shack yagi TV antenna? One would expect that with such
a long product lifetime, years of evolutionary development, the
availability of sophisticated modeling tools, and the need for more
sensitivity with OTA digital TV, that such antennas would be a
superior design. No so. I've reverse engineered two of these (that I
have on my roof) and found them to be abysmal. On some channels,
there's more gain in the reverse direction than in the forward. The
herringbone log periodic attempt is really quite omni directional with
the added detriment of lousy gain. From my numbers, it would seem
that these are designed on the basis of aesthetics and manufacturing
costs (using identical length elements) rather than performance.


[1] Incidentally, what is the one thing that you can't determine by
reverse engineering a product? Answer: design and production
tolerances. That's where things usually go awry and why industrial
espionage is still popular.

--
Jeff Liebermann jeffl@xxxxxxxxxx
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
.

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