Duporth Avenue: Pt 1

Over the Easter holiday of April 7-9, an antenna was erected on the seventh floor of a high rise apartment building in Duporth Avenue, Maroochydore on Queensland’s Sunshine Coast. This will be a two part entry.

Part one will focus on the geography of the region. Aside from the aesthetic appeal, the topography (captured by professional photographers) has important effects upon long distance FM reception and even permanent reception! Part two shifts focus onto the receiving system including MP3 recordings, photographs of the antenna system (with the panorama in the background), troposcatter from the north and the visual logbook of signal paths.

Receiving location

Local UHF television and FM radio broadcast sites were situated 23 kilometres south-west and 18 kilometres west of the receiving location. The elevation at the receiving location was 14 metres above sea level according to Hey, What’s That? path profiler. The Sunshine Coast Airport was located seven kilometres north, or a 12 minute drive according to Google Maps.

Within the surrounding few kilometres, the urban high rise strips in Duporth Avenue, Cotton Tree, Maroochydore Beach (high rise pictured), Alexandra Headland and Mooloolabah Beach are likely to have attenuated signals to the south-east.

Perhaps signal attenuation has positive effects. The result is a relatively empty FM band which is potentially far easier for achieving Sporadic E FM reception than another urban city such as Brisbane or the Gold Coast.

Hey, What’s That? theoretical path analysis

Significant path obstructions existed to the south and south-west according to the analysis. Aside from the aforementioned man-made concrete jungle, five kilometres to the south was Buderim Mountain range, pictured.

According to the Centre for the Government of Queensland at the University of Queensland:

…the Buderim formation has an elevation of under 200m and is more a rising plateau which extends for about seven kilometres. It has red soil, impregnated with iron oxide.

Also on the Buderim plateau, nine kilometres west was Kiels Mountain (151 m). Still focussing on the south and south-west, the most prominent terrain obstacles were these volcanic plugs .

The Glasshouse Mountains (pictured above & below) include Mellum (406 m, 26 km), Beerwah (556 m, 35 km) and the Tunbubudla Twins (338 m, 41 km). The D’Aguilar range presented another significant path impediment, including Mount Mee (501 m, 58 km).

The panorama to the north-west was ‘clear sailing’ according to Hey, What’s That? Eight kilometres north is Mount Coolum (207 m), the subject of the three photos below. Much further afield were the mountains of Eerwah (340 m, 26 km) and Cooroy (409 m, 28 km). The summit of Point Glorious was 25 kilometres west.

According to the Sunshine Coast Council:

Mount Coolum is a volcanic plug, 681 feet in height, rising from the coastal plain and with part of its base projecting into the ocean to form Point Arkwright.

Coolum district was the traditional land of the ‘Inabara’ or ‘Yinneburra’ clan of the Undanbi tribe of Aboriginal people, which was in turn part of the larger group known as the Kabi Kabi (or Gubbi Gubbi).

From the location of the antenna on the apartment balcony, the panorama (not pictured in this entry) included Mount Coolum in the distance.

The panorama from the north-northwest to the south-east was free of obstructions courtesy of the Coral Sea! Unfortunately there is no land in that direction to permit troposcatter. The largest islands towards the east are the southern tip of New Caledonia and the northern tip of New Zealand. During summer Sporadic E would be possible from these locations with respective hop distances between 1,435 – 2,208 kilometres according to the FM Scan Sporadic E Index.

Permanent troposcatter from the south

The path analysis suggests that the Buderim plateau may prove an obstruction five kilometres to the south and south-west.

Significant attenuation of signals to the south prevented reception of the Redcliffe community station just 66 kilometres away. Whilst it was very suprising at the time, the explanation now seems clear. The obstructions in the Redcliffe path include the Bribie Island National Park on Bribie Island (pictured) and the Glasshouse Mountains. Gold Coast stations 154 kilometres away were audible via troposcatter from time-to-time. The use of directional antenna arrays may explain why the Gold Coast broadcasts were not permanent non-DX signals. Suburban community stations were audible without issue from the Logan and Wynnum-Manly regions.

Towards the south-south-west and south-west, the Passchendaele and Toowoomba city broadcasters were audible without issue. Not much impedes a 244 km 80 kilowatt ERP national broadcast from Mount Magnus (962 m) near Stanthorpe. Similarly, the Toowoomba city elevation offset the southwest obstructions up to 156 km for the commercial (10 kW) and community (4 kW) broadcasters.

Permanent troposcatter from the west

Significant attenuation of signals to the west impeded high quality reception of CFM Kingaroy (15 watts) broadcasting merely 122 kilometres distant and CFM Dalby (600 watts) 187 kilometres distant. The obstructions to the westerly path include the Conondale National Park (pictured) situated between Jimna and Kenilworth. The Conondale National Park (328 m) is home to a number of beasts including the mountains of Langley (868 m), Allen (593 m) and Gerald.

In addition, the broadcast sites to the west (Kingaroy & Dalby) were obstructed by the volcanic Blackall range situated between Maleny (pictured) and Montville. Blackall range has an average altitude of 500 metres according to the Oxford Student Atlas. This hinterland region averages 450 metres according to Hinterland Tourism.

The attenuation may have been worsened by the highrise building itself. The location of the balcony provided maximum opportunities for eastern paths only. (Again, it must be conceded that there is no land or islands in that direction). However, pointing the antenna west was unlikely to penetrate the concrete and elevators. Improved signals from the west may have been achievable in the car.

Acknowledgments & References

This blogger is indebted to the authors of the following websites or publications which provided data used for the above commentary.

Bonzle Digital Atlas
Cocky Flies
Department of Environment and Resource Management
Explor Oz
FM List
Google Maps
Hey What’s That?
Hinterland Tourism
Oxford Student Atlas of Australia
Queensland Places
Sunshine Coast Council
UBD Street Directory of Brisbane

The copyright holders of photography included on this blog have licensed their works under the Creative Commons for non-commercial use (such as this not-for-profit blog) with attribution. To view more of their work, type the photographer’s name into Flickr.

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One Response to Duporth Avenue: Pt 1

  1. anonymous says:

    Photos make for a fantastic geographical presentation. The interesting topography of the Sunshine Coast in relation to the antenna location make interesting reading. Looking forward to Part 2 to see how the topography influences long distance radio reception.

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