[TowerTalk] Model This NVIS

[Jim Lux]

On 11/20/12 9:13 PM, N6FD wrote:
> Try 4nec2 it is free, reasonably easy to use and reasonably accurate.
> I'm not sure exactly how you are set up there,  but you should be able
> to model your antenna system.


the NEC2 engine doesn't do "buried wires"

You need to get something like NEC4

What I would do, though, is start with NEC2, and model it in free space 
and see what you get.


The wrench in the works is that NEC and similar will tell you the 
pattern and how much beams up into the ionosphere, but won't model the 
NVIS reflection back down.

>
> 73, Erich
> N6FD
> On 11/20/2012 5:48 PM, David Jordan wrote:
>> Hi Folks,
>>
>> Jamaca NVIS...
>>
>> -    four driven elements fed in phase (70ft ea) spaced 70ft apart,
>> 18ft AGL
>> -    four reflectors 5% longer buried just below the earth
>> -    four directors 5% shorter, 45ft AGL
>>
>> A cloud warmer with gain?  On air comparisons with a dipole at 55ft.
>> Most stations within 300 miles abt 20db stronger (using calibrated
>> attenuator) depending on F2 layer conditions.
>>
>> I wonder what the computer modeling programs would predict?  I don't
>> have one to try...
>