This article continues on from Implementation of G5RV inverted V using high strength aluminium MIG wire documenting review after 5 years operation under a wide range of temperature, humidity and wind conditions.
Above is a view of the steel mast with the Inverted V G5RV rigged from the top of the 11m mast using a halyard though a purchase on a small gibbet to offset the antenna and feed line from the mast. There are lateral guys at 7m height, and the left hand one is non-conductive synthetic fibre rope. Atop the mast is a 2m/70cm vertical.
Dissimilar metal connections
The antenna system contains significant connections between dissimilar metals at two points, the connection of feed line to balun and connection of feed line to dipole. (It would be possible to build the antenna without the latter terminal, but it is convenient to be able to separately raise the dipole and attach the feed line so it was built that way.)
Details of the connections appear in the original article.
Above is a close up of the detail of connection of the aluminium open wire feed line to a screw terminal on the balun. The wire is 5356 aluminium MIG wire, the screw and nuts are 304 stainless steel and the penny washers are 316 stainless steel.
The wire and washers were liberally coated with marine grease before assembly, sufficient for most to squeeze out, and the excess wiped off. The purpose of the grease is to prevent ingress of oxygen (in air) and water, the essential ingredients of galvanic corrosion.
Close inspection with a bright light shows the space between the washers is fully filled with grease and there is no visible hint of corrosion. (Note that 304 stainless does acquire a light brown stain in the weather.)
The resistance of the terminals was checked using a Kelvin low ohms meter from end of screw thread to wire (2cm from terminal), yielding 2.0-2.5mΩ. This is acceptably low and indicates excellent connection, not much different to the original and +1 year measurements.
Since the connection aloft uses the same protection scheme and the balun terminals showing no signs of degradation, inspection of the aloft terminals was deferred until a later annual inspection (and report).
There is no sign of fatigue failure of the antenna or feed line wires, and the feed line spacers show no degradation and have not grown moss or lichens (a risk in these parts).
The feedline option used was the Sotabeams 110mm ABS/PC spacers.
Above is the Sotabeams 110mm spacer threaded with the 1.6mm aluminium wire.
Above is a view looking up the feed line which is twisted and supported away from conductors (the lateral guy to the right is non-conductive).
Above is a view of the feed line approach to the cable entry panel. Again, liberal use of marine grease to exclude oxygen and water from the balun terminals.
Above is a close-up of one spacer after 5 years of service. The spacer has not been cleaned, there is some cobweb on it, but the surface has not crazed or cracked, it is still shiny, and there is no sign of moss or lichens which attaches to any weathered / degraded plastic surfaces here in the (Australian) Southern Highlands. Importantly too, the grip on the wires remains sound, there has been no apparent deformation of the plastic gripping fork on the end of the spacers.