NEC-LIST: Unusual modeling problem

Ed ...

        You do not say what is your frequency of interest. I use the
following table for HF antennas(above the ground, of course!).
Unfortunately I have lost the reference to the source of this data.
If anybody out there recognises this table, please let me have the
reference. I have also seen tables for other frequencies.

Soil parameters vary considerably with frequency as well as moisture
content (recent rain etc), and the 'accuracy' of the conductivity
figures represents a bit of wishful thinking!!! Permeability data
will depend on the mineralisation of the soil (eg the iron content)
and a direct measurement is probably the best way to go. If the
ground has been significantly disturbed, as I suspect is so in your
case, soil compaction will also change the parameters.

Regarding a modelling engine, something like Ansoft's FEM package
"HFSS" should be able to give you some answers - not cheap, though!!!

Earth Surface Type: Relative Conductivity
                        Dielectric (Millimho/m2)
                        Constant

Arctic Ice 3 0.025
Average Land 15 27.800
Desert Land 3 11.100
Dry Sandy Soil 15 1.000
Dry Soil 4 10.000
Fresh Water 81 5.000
Glacial Ice 15 0.040
Good Jumgle 15 30.000
Marsh Land 30 111.000
Medium Jungle 13 10.000
Poor Jumgle 10 2.000
Rich Damp Soil 22 15.000
Rocky Ground 4 1.000
Sea Water 81 4640.000
Thin soil over rock 7 1.500
Tundra 5 0.400
Very Dry Soil 4 1.000

Cheeeeeeeeeerz,
Alan

**************************************
Alan Nott BEE, CEng, MIEE
Senior Technical Specialist Engineer
Electromagnetics Cell
Software and Systems Engineering Unit
Army Engineering Agency
Tel + 61 3 9319 5889
Fax + 61 3 9319 5909
email: alan.nott_at_aea.sptcomd.defence.gov.au

-----Original Message-----
From: Ed Troy [mailto:etroy_at_aeroconsult.com]
Sent: Saturday, 20 May 2000 3:41
To: nec-list_at_ee.ubc.ca
Subject: NEC-LIST: Unusual modeling problem

I am looking to perform a strange simulation. I need to model the
propagation from one underground room to another through a hollow
plastic pipe in the dirt. Does anyone know of a program that will
model such a situation? I don't believe NEC will, but I could be
wrong. Maybe it will if I have the correct version? It is very similar
to a waveguide problem, but the walls of the waveguide consist of
plastic and dirt, rather than metal. Also, does anyone know a
reference for the electrical characteristics of dirt, such as
dielectric constant, permeability, permittivity, etc?

Ed
Received on Wed May 24 2000 - 06:41:12 EDT