NEW 21st
August 2023 - info from Keith GM4YXI :Antennas are
always a vital component of a successful DXpedition – perhaps second only to
location in importance. Since our second DXpedition, in 2013, we have used
vertical Moxon antennas on the 5 bands 20-10 with verticals for the lower
frequencies. These antennas have served us well but have always been located
‘on the beach’ or within a few metres of it. This is not possible at VK9XGM.
The location looks excellent, but we are on the edge of a relatively low
cliff with no beach access. We are not sure regarding the terrain around the
location, nor how much of it we can access, but feedback and images we have
seen suggest boulders and scrub. We are not convinced that the Moxons will
be a good choice for this location.
We describe elsewhere on this site our location. We
will have (as far as we can tell) a fairly unobstructed shot over a few
metres of land to the cliff edge from a bearing of about 60 degrees azimuth,
through North to West to about 210 degrees azimuth. South is not so great as
signals need to cross the island and some higher ground. From due East to SE
land rises a bit and will be our worst take off. Bearing in mind long path
openings to North America and short path to parts of South America (LU and
CE), we think our best bet will be vertical antennas on all bands. It is
doubtful that the Moxons gave us any useful gain or FB anyway.
We will be using verticals on 20-17-15-12-10 with
elevated ground planes of radials and feed points about 3m above ground. We
are factoring in only being able to erect six antenna supports, due to space
restriction. We have constructed and tested dual band verticals for 20+12m
and for 17+10m and these seem to work well. We will have a contingency to
disconnect either driven vertical element if there are interstation QRM
issues depending on bands in use. For 15, 30 and 40m we have monoband
verticals. Our 160/80m vertical is described elsewhere (modified from DJ0IP
design) and will allow operation on either band but not both simultaneously.
We may manage a beverage antenna for low band receiving but again, this
depends on space and access. We will take wires for another 10m and 12m
antenna in case we can find an arrangement to allow this for more
flexibility – allowing us to be on 10 and 17 or 20 and 12 at the same time,
should that be necessary.
As always, our plans may have to change once we get on
site and review the location....
Antennas at
VK9XGM :
160m Top loaded
vertical on 18m Spiderbeam pole (shared with 80)
80m Top loaded
vertical on 18m Spiderbeam pole (shared with 160)
40m vertical on
12m Spiderbeam pole – elevated ground plane
30m vertical on
10m pole – elevated ground plane
20/12m verticals
on 10m pole – elevated ground plane
17/10m verticals
on 10m pole – elevated ground plane
15m vertical on
7m pole – elevated ground plane