VK9XGM                Antennas .....

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