|VK9CZ - Antennas|
Antennas are the key to success on any DXpedition - especially when you are 15000km from the U.S.A.
We are a bit old-fashioned (some might say obsessive!) when it comes to antennas. All VK9CZ antennas will be resonant antennas for best results - no ATUs, traps, coils or linear loading devices will be used. All VK9CZ antennas will be as efficient as we can make them and as close as possible to the ocean.
Having all monoband resonant antennas leads to somewhat difficult choices - antennas have to be : fed directly with 50 ohm coax, to have <1.2:1 SWR i.e. >21dB return loss (ideally at both the CW and SSB ends of the band), be lightweight, ideally have some gain/directivity, be easily installed.
The weight of coax cable is also an important consideration - for example 25m of Aircell5 weighs 1.02kg, 30m of Aircell7 weights 2.44kg, whereas 25m of RG213U weighs 3.3kg. VK9CZ has about 400m of coax - Aircell5, Aircell7 and M&P Ultraflex7. We are taking 10 Spiderbeam and other fibreglass poles as antenna supports. Sadly the useful palm trees at the water's edge which we used in 2013 have been cut down so that the shoreline could be sand-bagged to reduce erosion.
Why use Spiderbeam poles instead of cheaper alternatives? We've found from experience that cheaper fibreglass poles are thinner and weaker and tend to crack or break more easily - not something you want to happen during a DXpedition. Spiderbeam poles can do a lot of bending and still survive!
The VK9CZ antenna line-up is shown below. We are taking two 5-way remote coax switches and one Alpha-Delta 4-way manual coax switch for maximum flexibility.
|RX antennas||200m long Beverage (to Europe) and FO0AAA RX loop (rotatable)||Low level + suspended from rope|
|160m||Top-loaded vertical with 4 elevated radials||18m Spiderbeam pole|
|80m||Top-loaded vertical with 4 elevated radials||18m Spiderbeam pole|
|40m||Quarter-wave vertical with 2 elevated radials||12m Spiderbeam pole|
|30m||Quarter-wave vertical with 2 elevated radials||9.7m fibreglass pole|
|20m||Vertical 2-element Moxon||10m fibreglass pole|
|17m||Vertical 2-element Moxon||10m fibreglass pole|
|15m||Vertical 2-element Moxon||7m fibreglass pole|
|12m||Vertical 2-element Moxon||7m fibreglass pole|
|10m||Vertical 2-element Moxon||7m fibreglass pole|