[TowerTalk] NEC 5.0 ???

[Artek Manuals]

Also I do know there are differences between NEC 2, NEC4.1 and NEC 4.2 
on how each of them handles conductors on or near earth. NEC 2 does not 
deal accurately (?) with wire close ( some small fraction of a 
wavelength or less) to earth. NEC 4.1 does and "adequate" job with wires 
"on the ground" and possibly buried to some degree. Reportedly Rudy, 
N6LF found errors with the ground model and worked with Jerry/Gerry (?) 
Burke and supposedly that led to NEC4.2 . I do not have exact knowledge 
of what those errors were or how they affected what conditions and to 
what degree though I am told that for most things we deal with at HF 
that it wasn't significant. I have had recent conversation Rudy  on 
other topics related to measuring ground characteristics using a OWL 
probe and good VNA but we did not get into the various releases on NEC 
in the process

STILL: I would like to get BACK TO MY ORIGINAL QUERRY

HAS ANYONE OUT THERE ACTUALLY USED THE new NEC 5.0 windows executable as 
supplied by Lawrence Livermore Labs?

Dave
NR1DX

On 3/12/2021 10:04 AM, Lux, Jim wrote:
> On 3/11/21 11:57 PM, M�ximo EA1DDO_HK1H wrote:
>>
>> Hi Jim,
>> As far as I know, for Cubical Quads, MiniNEC (Mmana) gets more 
>> accurate results than NEC2/4.
>> I haven't tested myself but it's what I remember to read somewhere else.
>>
>> Do you know how NEC5 performs on same Cubical Quads?
>>
>> Thanks
>>
>> 73, Maximo - EA1DDO
>>
>
>
> No idea off hand, since I don't use MiniNEC or MMANA. A lot of the 
> issues reported with NEC are for NEC2, which has problems where wires 
> join at acute angles, and with numerical precision with very short 
> segments.� NEC4 doesn't have those problems.� I would *think* that 
> NEC4 would do fine on a cubical quad - it's wires, it's simple, 
> there's no "rapid changes in diameter" or "wires of radically 
> different cross size connected at an angle" or "wires connecting to 
> surfaces".
>
>
> Both are method of moment codes, so the basic solution approach is the 
> same. The differences are in how they represent the current along each 
> segment.� NEC4 is significantly better when dealing with transitions - 
> For all the codes, they make an assumption of what the current 
> distribution along a segment is - flat, sloped, typically, some sort 
> of A + B*sin() + C*cos().�� What NEC4 did is change this a bit to 
> A+B*sin()+C*(1-cos()) to improve the numerical performance for very 
> short segments.� With NEC2, if you took a dipole and made it 
> successively smaller and smaller segments, at some point, the solution 
> blew up - too many equations with terms that are either 1.000000001 or 
> 0.00000001 and even with double precision it didn't work.
>
>
> The other significant difference from NEC2 to NEC4 is a difference in 
> where the "current filament" is considered to exist. In both versions, 
> the current is assumed to be entirely along the axis of the segment 
> (there's no "around the segment" current flow).� In NEC2, the current 
> is assumed to be at center of the wire, but in NEC4, it's on the 
> surface of the wire.� For long straight uniform wires, this makes no 
> difference, but on a step or at a corner, or where wires are close 
> together, it does make a difference.
>
>
> https://physics.princeton.edu/~mcdonald/examples/NEC_Manuals/NEC4TheoryMan.pdf 
>
>
>
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Dave Manuals at ArtekManuals.com www.ArtekManuals.com

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