Re: [TenTec] gas on the fire

[John <jh.graves@verizon.net>]

My experience is as a self taught student still learning about how the 
NEC models work and I am also trying to move from EXNEC to 4NEC2.  What 
I am really trying to say here  is that if someone else sees anything 
incorrect, I know I am on somewhat shakey ground, so please feel free to 
correct me.
When the NEC program is opened, one of the first tasks is the wires 
(antenna) definition.  This is done on 3 axis's (X, Y, and Z as 
Vertical).   The wires definition allows the definition on all 3  axis, 
so an antenna can be defined as lying on (extending for some distance 
along) the X axis and be some amount  of height (defined in meters, feet 
or wavelength) above ground on the Z axis.    This places the antenna, 
either vertical or horizontal, the defined distance above ground (which 
is also definable.) As the height above ground is increased, changes in 
the pattern diagram will show changes (plus or minus) in the takeoff 
angle.  This would seem to indicate that NEC is sensitive to ground 
changes which can include height among others.  Although I have not done 
any extensive exercises, I believe that the program will also be 
sensitive to the ground conditions (why make ground definable if there 
is no sensitivity) as well as showing the effect of defined ground 
planes or radial fields.
I hope this helps and provides some insight into your question.


John / WA1JG


On 5/21/2012 5:00 PM, Richards wrote:
> On 5/21/2012 3:47 PM, Paul DeWitte wrote:
>
>
> > First, I think that if you modeled a ground mounted vertical and the same
> > vertical at 330 feet above ground, you might find the radiation pattern
> > (take off angle) would not be the same for the two installations (just my
> > guess).
>                 This makes sense to me.   Can the NEC-based modeling
>                 programs do that ?   They seem to consider different
>                 ground conditions... but what if ground is 350 feet away ?
>
>                 Good question.
>
>
> > Second, so far no one has said anything about grayline DX (or about that
> > time) when some claim that a dipole works better than their vertical. This
> > is on the low bands, dont know about higher freq.
>                 More of the mysteries of propagation ...  I think
>                 many hams know very little about the vagaries
>                 and effects of propagation --  and I am one who
>                 needs to learn more about this aspect of radio.
>                 Hams often talk about take-off pattern, yet blithely
>                 ignore what might be happening to the signal after
>                 it leaves the the back yard.
>                 
>
>
> > About S meter accuracy. You either hear them or you dont. If you can hear
> > them and work them, it dont make any difference what the S meter reads.
> > I worked a lot of DX on my Omni C that did not move the S meter needle, but
> > they made it into the log.
>                 I thought there was a school of thought that
>                 based the signal strength component of signal
>                 reports on S-meter readings - in which case it would
>                 matter to them whether or not S-meters were
>                 1)  accurate,  and 2) consistent between rigs.
>                 If so, then I think this would be a worthy topic
>                 for beating to death.      ;-)
>
>
> ----------------------------------  K8JHR  ---------------------------------
>
>
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