Re: NEC-LIST: Efficiency of Short Dipoles

Greetings Dr Fourie (and knowledgeable lurkers):

Reference your message 04:59 PM 12/3/97 GMT+2 to Prof. Baker
>
>I just noticed your reference to mu(r) of stainless steel rope as a
>potential source of additional loss in HF antennas,
>
        Although I believe you did not start this thread, I am
replying to you because this is my first sortie into NEC-List, and I'm
unsure of the proper netiquette.

        I might be accused of "topic drift", but I must satisfy my
curiousity piqued by mention of ferrous materials in an antenna
system. My understanding of "good practice" is to avoid use of such
materials in the RF current-path, or suffer the consequences of
distortion products (harmonics, intermodulation).

        Perhaps I blinked and missed a key point - e.g. perhaps the
contemplated antenna may only be intended for receive purposes, where
the non-linearities would not be as important (or for a low-power
single-channel application)?

        We are planning a shipboard broadband system (upgrading to up
to eight simultaneous transmit circuits, up to 8KW peak power), and
our design efforts have been to exclude ferrous materials from the
current path (while satisfying selection criteria for dissimilar
metals in a salty environment).

        While this forum is for NEC-related activity (and we are
having NEC used as part of our investigations into the best approach
before we go to the "1:1 model"), I'm sure there are persons here who
can also confirm/deny "conventional wisdom" in the use of ferrous
materials in an antenna system. And are there "magic" formulations of
stainless-steel with linearity approaching that of copper, aluminum,
phosphor-bronze ... ?

TIA;

  David G. Robinson
DGMEPM/DMSS 8-3-4
   (819) 994-8487
   FAX 997-2194
Received on Wed Dec 17 1997 - 12:52:13 EST