Re: NEC-LIST: Monopole above soft water

   Hi Alexander,
   I try to answer to some of yours questions, and I hope don't talk
   rubbish.
   1) Is NEC's ground model applicable to something like softwater
   (epsilon~=80, relatively low losses)? I've never used SOMNEC before,
   so this is something new for me.
   - Yes it's possible, in NEC you can define the epsilon and the sigma
   of the ground (softwater): the comand is "GN".
   2) Modelling the immersed part is impossible with NEC2, but I consider
   testing two things :
   a) Model a monopole just in contact with the water's surface, like
   NEC2 allows (I'm only interested in the radiation pattern, not in
   calculating the input impedance).
   b) Instead of a discrete contact, have a network of short radials
   converging to the base of the monopole.
   What do think above approaches? Can one neglect the underwater
   component of the buoy, or is my approach pointless?
   - Is important to understand if the monopole in your buoy is in
   electrical contact with the water, and if part of the wire is under
   the water. If you are interested only to the radiation pattern the
   best for you is to implement the real distribution of the current in
   the section of monopole over the water, and this not implies that the
   wire must touch the ground (the water).
   I'll explain:
   if the monopole is not in electrical contact, for esample you can
   simulate the monopole in open space, determine the intensity of the
   current in the section that must be over the water, then you can force
   this current in your monopole that is placed over the water without
   touch. -> Obviously this is not the best because in this way you can't
   consider the interaction between the section above the water and the
   water that modifies the real distribution of current in the wire, but
   is a good first approach.
   If the monopole is in electrical contact whit the water, your way is
   good but I believe the the network of short radials is pointless (I
   believe!!!).
   3) Do you know of any literature on this or a comparable problem? (eg:
   propagation studies on inland navigation).
   - No I don't. Sorry.
   I hope this are some good suggest.
   Regards
   Mirko Dionisi
   Ing. Mirko Dionisi
   ABS - Electromagnetic Analysis
   Consulting Engineer
   I.S.L. - Ingegneria dei Sistemi Logistici
   ALTRAN Group
   Ospedaletto (PISA) - Italy
   Mail: mirko.dionisi_at_isl-altran.it
   Web: www.isl-altran.it
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