NEC-LIST: Use of Galvanised wire verses stainless

Dear Nec-list,

We currently deploy small satellite relay data loggers (see web site
below) on whales and seals and we have a debate currently running on
the type of antenna wire. Both types of wire are sold in Ship
chandlers as rigging wire. We use it to survive the wear and tear
given to it by the animal. I know it is not ideal in terms of
conductivity. My question is this is been any work being reported on
the merits of different wire types in a sea water environment. The
unit lifetime can be around 9 months. We have had back galvanised
wire antennas with rust cover ~ 1/3 length which would have probably
affected the surface conductivity. SS antennas tend to suffer more
fatigue problems at the point where it exits the potting material -
polyurethane. The antenna is cut as a 1/4 wave whip above a small
ground plane - the surrounding sea provides the rest of the ground
plane. Working frequency is 401.65 MHz +/- 4kHz, input power ~ 0.5W.

We have modelled this under NEC2 it gives a reasonable match at 50
ohms with the physical structure used.

Paul Record
SEA MAMMAL RESEARCH UNIT
Gatty Marine Laboratory
University of St.Andrews
St. Andrews
FIFE KY16 8LB
Tel: 0044 1334 462630 Direct: 0044 1334 463628
Fax: 0044 1334 462632
SMRU web site http://smub.st-andrews.ac.uk
email : p.record_at_smru.ac.uk
Received on Thu Apr 29 1999 - 15:55:56 EDT