TX3A Chesterfield Islands DXpedition


We try to tread the thin line between minimizing the equipment we carry and being effective, especially being able to put out a good TX signal on 160 meters.

Transport: As before, we will use the motor vessel Pedro (previously called Varzin). To meet legal requirements, we will first have to clear French customs and immigrations in New Caledonia. This requires that we first cross from Australia to New Caledonia, a 950 nautical mile (1800 km) trip. We intend to do this in late October. We intend to refuel and re-provision (and make any repairs needed) in Numea. As the boat does not have the fuel capacity required, we will be carrying additional diesel fuel in bladder tanks. We will have a tight limit on the amount of equipment and generator fuel we can take. (And other stuff, like food and comfort items.) This is no easy feat on our ocean expedition either, with the geographical and meteorological challenges we face. Establishing our TX Antenna was difficult enough, without even considering other technologies like internet or mobile broadband issues. Hopefully, it should be an easy ride and we won't run low on resources at any inconvenient point.

TX Antenna: We are using a modified version of the proven VK9GMW antenna. The new configuration has three 19 meter tall Spider-Pole masts that support a T instead of the Inverted L. We have also eliminated the 80 meter down-lead and grounding relay. (Not because it does not work, but because T configuration does not need it.) The antenna is erected over sea water in a small lagoon, which almost dries at low tide and has about 1.5 meter of water during high tide. For details of the VK9GMW antenna see http://vk9gmw.com/documents/VK9GMW_ANTENNA.pdf

RX Antenna: On Mellish Reef we had very difficult RX conditions: on 160 meters a very active Monsoon season over Indonesia was generating strong QRN on most nights. Back home we experimented with a rotatable Waller Flag, but found that it was mechanically too complex for installation on an island, and especially in high winds (which we have most of the time). Instead, we have developed and installed what we call the TX3A Double Half-Delta Loop (DHDL). This antenna uses two supports to hold what essentially are two back-to-back half delta loops. No special phasing circuit is required and performance is almost 3 dB better that what can be obtained with a single delta or flag.

A description of the DOUBLE HALF DELTA LOOP antenna used by TX3A can be downloaded from the following URL: http://tx3a.com/docs/TX3A_DOUBLE_HALF_DELTA_LOOP.ZIP

Two K3 Transceivers

Two SGC SG-500 solid state amplifiers combined for 500 W output.

A single 240 V, 1.5 kW Honda generator, six 12 Volt car batteries, and three low cost battery chargers. All equipment will operate from 12 V DC.

Feedback:  info (at) tx3a.com