Fw: Re: [TowerTalk] DB's, ad nauseam

[wa4dou@juno.com]

--------- Forwarded message ----------
From: wa4dou@juno.com
To: W8JI@contesting.com
Date: Sun, 23 Jul 2000 19:13:13 -0400
Subject: Re: [TowerTalk] DB's, ad nauseam
Message-ID: <20000723.191711.-1032287.17.wa4dou@juno.com>

Hi Tom,
  I think you're wrong. International short wave broadcasters have, in
some instances, used ionspheric focusing as a means of enhancing their
signals into an area, taking advantage of this phenomonon. Last month, in
QST, Tom Schiller(hope i spelt that correctly) wrote an article which
recognizes this phenomonon. I have personally experienced it. Basically
its this: An antenna with well known and predictable characteristics,
compared to another lesser antenna(also with known and predictable
characteristics), producing results via ionspheric propagation
disproportionate to and far in excess of any known  differences between
the two. Do you have your own stories to tell about this phenomonon Tom?
73 Roy WA4DOU
-------------------------------------------------------------------------
-------------------------------------------------------------------------
-----------------------------------------------------------------------
On Sun, 23 Jul 2000 20:23:44 -0400 "Tom Rauch" <w8ji@contesting.com>
writes:
> > power levels at differing angles of radiation. We all know there is 
> no
> > such thing as a perfect mirrorlike reflection going on in the 
> ionsphere.
> > Indeed it varies not only time to time but also angle to angle and 
> time to
> > time. Sometimes it appears to be quite linear and sometimes very 
> non
> > linear. Its too simplistic to say that i raised my antenna gain 1 
> or 2 or
> > 3 db, or whatever, and what i heard is an accurate representation  
> of that
> > theoretical change. Sometimes, due to the non linear reflectivity, 
> the
> > change may actually be greater.
> 
> Non-linear reflectivity only occurs when the transmitters signal has 
> 
> moved all of the available charges in some area the reflective 
> medium, and it runs out of charges to move.
> 
> The result is the signal re-radiation from the ionosphere no longer 
> follows the transmitter power in a linear manner, the reflected 
> power increases at a SLOWER rate than the transmitted signal! 
> 
> Reaching that effect requires ERP levels in the order of millions of 
> 
> watts.
> 
> If you are seeing some other effect, where the increase is more 
> than the transmitter ERP increase, you have experienced a 
> measurement error. It could be caused by QSB or poor meter 
> calibration.
> 
> Sometime we also fail to consider we might be using the slope of 
> the lobe of an antenna. Another antenna with about the same gain 
> on the nose of the main lobe might actually have provide radically 
> different gain at that off-peak angle.
> 
> The ionosphere is absolutely linear for power level changes at 
> normal power levels.
> 
> 
> 73, Tom W8JI
> w8ji@contesting.com

________________________________________________________________
YOU'RE PAYING TOO MUCH FOR THE INTERNET!
Juno now offers FREE Internet Access!
Try it today - there's no risk!  For your FREE software, visit:
http://dl.www.juno.com/get/tagj.

--
FAQ on WWW:               http://www.contesting.com/FAQ/towertalk
Submissions:              towertalk@contesting.com
Administrative requests:  towertalk-REQUEST@contesting.com
Problems:                 owner-towertalk@contesting.com