ZL9HR – Antenna Choice and Location

The Beeman Point location for the dxpedition station is on a hillside on the northern side of Perseverance Sound. There are permit restrictions on where we can position antennas – they will have to be close to the old meteorological station and some distance away from the shore. Many island dxpeditions have been hugely successful using vertical antennas on the beach or in the water. However, Campbell Island is not a flat coral atoll, it’s a mountainous volcanic remnant with a rocky shoreline where our antennas are not permitted. Consequently, we will use the features of the landscape to enhance the performance of horizontal beam antennas on many bands: 2- or 3- element Spiderbeams  or 2-ele Moxons on 10, 12, 15, 17, 20 and 40 m. There is a ridge to the south of Beeman Hill where several antennas will be located; their effective height will be increased in most directions due to their ridge-line site. Others will be closer to the CW camp, on the hillside near the old meteorological station. They will have a good take-off along the direction of Perseverance Sound, which will favor LP-EU and NA. Vertical or inverted-L antennas will be used for 30, 40, 80 and 160. Both antenna groups will be accessible from both the SSB and CW operating positions, as necessary. In general, this is a similar approach to the ZL9CI team, who successfully operated from the same location in 1999.

The map below shows the approximate location of the operating site, with the direction of various countries indicated.

The approximate positions of antennas and operating positions are shown on the aerial photo below. Red and Blue Area – Permitted locations for antennas
Green Dots – Radio equipment
Yellow Area – Exclusion area – Weather station equipment

The effect of the local terrain on the antenna performance can be estimated using the HFTA program. From either the central (ridge) antenna site (two red ovals in the image above) or the hillside site (blue line next to building), the terrain profile towards Italy or France looks like this:

The ridge location (red) has a decent shot towards EU via SP, but the hillside (green) is not good in this direction (the antenna is looking into the hillside). How do these terrain profiles affect antenna performance? Looking at the ridge location it seems like it should be good. Below are gain plots for a 20 m 2-ele horizontal yagi, mounted 30 feet above local ground for the ridge and hillside locations. For reference, the blue lines show performance over a flat surface, with antenna mounted at either 30 (dark blue) or 100 feet (light blue).

Clearly the antenna on the ridge gets a good performance boost compared to the same antenna over flat ground. The purple bars indicate arrival angles for signals on this path – the antennas don’t access the lowest angles, but that’s not really a problem since the surrounding hills will take care of them, anyway!

The terrain towards the US or EU via LP looks like this:

The antenna (colored lozenges) is mounted 30 feet above the local ground, which is about 50 or 75 feet above sea level. Again, the red line is the terrain profile from the ridge location and the green line for the hillside location, with blue being reference flat ground, with the antenna 30 feet up. The takeoff is excellent for both sites in this direction, with the ground sloping down towards Perseverance Sound. This time looking at a 2-ele 40 m beam, the antenna gain is shown below:

 At 30 feet high over flat ground (dark blue), the 40 m 2-ele horizontal beam is clearly a cloud warmer. However, put it on the ridge or hillside, and it becomes an effective performer (light blue, for comparison, is a 100-foot high 2-ele over flat ground). The purple bars on the plot illustrate the angles of arriving signals on a US-ZL path – the 2-ele Moxon should work fine for these paths. We will also have verticals for 40 m and the other low bands, and will work with our NZ DOC representative to ensure that they are as well-sited as possible.

The result from running the same HFTA analysis, but on a 20 m 2-ele Yagi, in the direction of the US and EU-LP gives the result below (color codes the same as for the 40 m plot). This is the perhaps the best take off of all from Beeman Point, with a good effective height of the antenna (mast plus local terrain) looking directly onto a path across the water in Perseverance Sound.

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