This reminds me of an experience I had with a new antenna. After working
several days installing a new antenna, I attached it to an a/b switch to
compare it with my old antenna. I was delighted, the new antenna was always
better !!! Then to my dismay I saw I had the switrch reversed ... oh boy... I
changed the feeds, and continued the test. Guess what.. the new antenna was
still always better.
Lesson learned .... human nature and switching antennas in face of QSB.
John K9DX
> From: w8ji@w8ji.com
> To: topband@contesting.com
> Date: Wed, 6 Mar 2013 08:00:56 -0500
> Subject: Re: Topband: Elevated Radials
>
> > I've noted your postings re elevated radials to replace deteriorated
> > buried
> > radial fields under broadcast towers. I'm familiar with the work and the
> > results. This work, of course was done by professional broadcast engineers
> > with significant instrumentation at their disposal. Of course, they also
> > had
> > to measure the field intensity in the far field and file it with the FCC.
> > Their work seemed to show that, once we have installed 4 elevated 1/4 wave
> > radials we're reaching the point of "diminishing returns" and that little
> > is
> > to be gained by increasing the number of radials beyond 4.
> >
>
> Charlie,
>
> We shouldn't be critical of people. People believe what they want to
> believe, including you and all of us. Here is how it really works:
>
> 1.) In an FCC measurement, a test signal is sent and the SLOPE of
> attenuation in the far field is used to estimate earth conductivity.
>
> 2.) A graph (or formula, but generally a graph) based on the measured
> attenuation slope is used to predict the expected signal at standard
> distances.
>
> This creates a problem, because if we look at measurements along a line in
> any direction, they are often all over the place at various points. The
> engineer has to smooth the readings out and match a curve, which gives the
> engineer considerable lattitude depending on how he does the smoothing.
>
> Even more important, ONE measurement system over one ground that contains
> multiple old radials of unknown condition and one set of soil conditions
> does not mean it applies to other conditions.
>
> By far, the most accurate way to determine a change is to do a direct
> measurement of what we want to know in an A-B comparison with only the
> variable we are trying to define changed. This takes out the human emotional
> factors and other errors, and then rememmber it applies to that case.
>
> No matter how much we want something to be true, or how much we like or
> agree with something, this is just how it **really** works. It's human
> nature to gravitate toward a system that takes little room and installation
> time, doesn't cost much, and is an "it always works this way" silver bullet.
>
> We should not pick at people and call people names who point out obvious
> flaws and limitations in faith-based conclusions. Anyone who has objectively
> made measurements realizes there is no single universal answer, no matter
> how nice it would be if there actually was one.
>
> 73 Tom
>
> _________________
> Topband Reflector
_________________
Topband Reflector
|