It’s all Mee

On the evening of April the 23rd, a spontaneous decision was made to travel to Mount Mee. This mountain is also part of the D’Aguilar range. Access was via Dayboro (below).

Once at the destination (below), altitude and temperature measurements were taken.

The photo (below) illustrates conditions. The weather was fine with a temperature of 27.8 degrees celsius. The altitude was approximately 580 metres above sea level. There was no fog present (one indicator of potential tropospheric ducting).

The altitude is no match for the mountains of Glorious and Nebo on the same range, but the location is probably easier to navigate. Whilst permanent FM reception suffers at Mount Mee, there are far fewer residential streets. That means more remote parking spots are available to choose from. There is also less risk of getting the car bogged in mud.

This video shows broadcasts from Rocky & Bundy, including:

• 105.5 News Radio – Rocky (QLD) – 80 kW – 435 km
• 103.1 Radio National – Rocky (QLD) – 80 kW – 435 km
• 93.9 4RUM Hitz FM – Bundy (QLD) – 3 kW – 252 km

Prefer a longer recording of News Radio?

This video shows broadcasts from the Kingaroy CBD and an unknown Christian station. If readers have any clues regarding 100.5 MHz, please don’t be shy! None of the stations filmed have been heard in the city:

• 93.1 Radio TAB – Kingaroy (QLD) – 25 watts – 108 km
• 96.3 K FM – Kingaroy (QLD) – 50 watts – 108 km
• 100.5 Was ist diese Station?

With the car facing north, co-channel interference from Lismore was alleviated. As a result, RDS (below) was possible from this 5 kilowatt station, 101 kilometres away.

RDS (below) was taken from this 200 watt translator, 79 kilometres north.

The aforementioned Mount Mee highlights were made with a ‘marginal’ Hepburn tropospheric index of 1.4.

As good as it gets

Last year, memorable mountain top reception was heard at the same spot. On those occasions, moderate tropo ducting prevailed; so weather conditions were optimal for some planned mobile FM madness.

1 May

98.3 2NOW Now FM Mt Dowe – Narrabri – 100 kW – 435 km

10 May

107.9 Hot FM Mt Archer (pictured below) – Rocky – 10 kW – 471 km

The following bloggers have photographed D’Aguilar NP. Their travels and observations are definitely worth reading:

Mt Mee Wedding
Relocation to Mt Mee
Sunday drive to Mt Glorious
Day trip to Mt Nebo
Camping at Archer Creek

A previous trip to Dayboro can be found here. Coming up: the final entry from Mt Glorious.

Station logos are solely provided for the purposes of research & education under the Fair Use provisions of the Copyright Act in this jurisdiction.

Sounds of the shire

It seems clear that Youtube viewers have different preferences from the person shooting the footage! The videos that take minimal effort to create attract viewers whilst the more esoteric footage does not. This must be what Lynyrd Skynyrd (from 1987, fronted by the late Ronnie Van Zant’s brother, Johnny) feels like when they play the exquisite Sweet Home Alabama live.

Sunset – The Antenna – General observations

 

 

Awesome shortcuts for Long Distance DTV reception: part one

Achieving success with weak signal tropospheric reception is attainable by utilizing your laptop, notebook or netbook computer rather than a set top box. This writer tries not to use the computer for entertainment, preferring to buy stand-alone devices. But as a wise Homer once mused to his amazement: ‘Computers can do that?’ – hell yeah! This article is an attempt to explain why a set top box may be considered redundant for weak signal purposes.

Use a tuner specifically designed for mobile DVB-T reception. Manufacturers test receiving performance at speeds approaching 150 kilometres per hour. The AF9010 DVB-T Demodulator is one such integrated circuit. The Genius TVGo (third revision) is one of the multitude of USB tuners which contains this chipset. Here up the creek, that $60 Genius consistently outperforms all the set top boxes (which cost considerably more) on both rooftop and indoor yagi antennas. Equivalent tuners that utilize the same Microsoft BDA drivers and AF9015 Demodulator are available from $20 from Hong Kong. An example.

Whilst any indoor antenna system may yield undesirable results in this country (because of the relatively low transmitter powers assigned), it is progressively-minded to consider those USB cards offering dual diversity antennas. Manufacturers claim these provide significantly better reception of weak signals. One manufacturer, Elgato claims:

EyeTV Diversity contains a Digital Signal Processor (DSP), which uses information from both tuners to generate the best signal possible…

The result of this Antenna Diversity (AD) and multi-tuner technology is superb reception deep indoors, in weak DVB-T coverage areas, and at high speeds. In tests, the technology provided good reception in 95% of locations within the home (compared with 67% for conventional receivers), and a 50% improvement in the quality of the television signal.

Once the USB DVB-T tuner is installed, command-line software will permit Viterbi decoding of weak signals. This step provides confirmation of DVB-T signal reception where signals are terribly weak! Such signals will not yield any picture nor show any indication of life on any set top box signal meter under ownership.

For Linux (above; tested under Terminal in Ubuntu 12) DVB Tune is recommended. The human translation for the above screenshot is that the ‘Tuner Front End has attained Viterbi’ from King Muzza’s favourite transmission site.

For Windows (tested under MS-DOS in Windows XP) Scan Channels BDA is recommended. In good faith, both tiny software packages are believed to be based on the GNU Library General Public License (GPL) with the Linux operating system, hence freely downloadable.

Koos van den Hout is a Systems Administrator for a department at the Utrecht University in Holland. Koos extolls Linux software such as DVB Tune on his exquisite blog concerning weak signal ‘DX’ DVB-T reception:

Some signals are very weak, to try and find out whether those are actually valid dvb-t signals I use dvbtune or zap to tune to the frequency (and either try to guess modulation, error correction and guard interval or let the automatic tuning in zap do its work), watching the signal strength and error rates and then use dvbsnoop in another window to try to get valid data from PID 0x10 which can give a hint to what services are active on that channel.

Further discussion

DVBTune in practice
Tuners with the AF9015 as ‘guts’
Installing drivers for AF9015-based tuners in Ubuntu/Linux

Postscript

Last night the writer had a play around with an old BT848 based analogue television tuner card. These cards with full Personal Video Recorder (PVR) facilities were ground breaking in the 2000’s, and notoriously popular for de-scrambling cable television, according to some anonymous sources!

One of the advantages of analogue is that noise can be readily seen in the video. And of course it is a drawback in comparison to digital! The same applies with regard to FM versus DAB Plus. RF ‘noise’ from the computer itself (in this particular instance, a desktop computer) presents some challenges which will be discussed very briefly here. Why? Because interference is the modern enemy of radio reception, in this blogger’s opinion. The more it is discussed the better we can equip ourselves with some potential defensive positions!

Laptops are often considered preferable for receiving weak or long distance television signals. The interference generated is often less problematic than what spews from desktop systems. Use of battery power is recommended. In a portable computer, mains adapters and battery rechargers are notorious sources of interference.

For further reference, the VK Logger offers a wonderful and simple dialogue here and here. The discussion is applicable to both radio and television signals.

Massive kudos to Koos van den Hout.

The shire

Laguna Lookout, Noosa Heads

Laguna Lookout is located in the Headland Section of Noosa National Park. Altitude information is unknown, but utilizing Bonzle, it is crudely estimated that Laguna Lookout has a height of 105-131 metres above sea level.

Below is a boarding video recorded by Plummet Longboarding. The ride starts from the summit of the Laguna Lookout.

The view is not bad, either! Gwirionez documents the panaroma concisely.

Idling in the crowded Laguna Lookout carpark for about two minutes, stations including Radio National from Coffs Harbour (distance: 437km, azimuth: 183°) & Rockhampton (distance: 392km, azimuth: 318° – much weaker) were receivable on the Blaupunkt Twinceiver. Other tropospheric scatter audible during the rain was from Bundaberg & Passchendaele (distance: 269km, azimuth: 207°). Note all other stations from Coffs apart from 99.5 MHz are blocked by local broadcasts on the Sunshine, Cooloola & Fraser Coasts.

Images from the local Sunrise Road translator site (distance:10km) & Cooroy’s Black Mountain (distance: 24km) were significantly problematic throughout the shire. Based on the brief scan undertaken, no such issues were noted at this lookout.

Mount Tinbeerwah, Tewantin

The altitude of Tinbeerwah is 265 metres above sea level. It is a favoured destination for climbers. But for the biggest thrills, it is best traversed using a unicycle!

Alas, in the two trips made to the lookout, the most popular activity observed was much simpler… Watching the sunset.

Bruce C documents this thoroughly in this video.

At the higher sections on the Mount Tinbeerwah walking track (leading to the summit) Rocky’s Radio National on 103.1 MHz (distance: 384km, azimuth: 320°) was audible via troposcatter.

The Dabbler’s Dream™ portable receiver (on steroids: modified with an extended telescopic antenna) revealed no traces of Coffs Harbour. Considering that aforementioned local sites are 5km & 13km away, that is probably no surprise. Consider the impeded portable performance experienced by this blogger at Cooloolabin Dam.

It seems certain that RN heard on the portable was definitely the Rocky broadcast (rather than a mistaken image of the local 20 kW broadcast) because other Rockhampton Mount Hopeful broadcasts were also audible with heavy fading in the Tinbeerwah carpark using the Twinceiver.

In-car video of Coffs (distance: 438km, azimuth: 181°) was recorded at Lake MacDonald’s Mary River Cod Park upon darkness. Lake MacDonald adjoins Tinbeerwah. With any luck, the documentary evidence will be uploaded by the end of the week. In these suburbs, jet scatter along Lake MacDonald Drive, Cooroy-Noosa & Sunrise Roads seemed to occur between 5-6 pm daily.

Radio path data sourced from FM Scan.org using the Locate Yourself Precisely algorithm. Videos sourced from Youtube.

Tropospheric digital reception

Digital broadcasting systems such as DAB-T radio & DVB-T television can enable an enthusiast or free-to-air consumer to receive high definition 1080p digital video broadcasts and multiple channels without signal degradation such as noisy ‘snowy’ video. (From a consumer’s perspective, it is not insignificant that Wimbledon & the AFL are sometimes only shown on the digital video subchannels which perhaps forces viewers’ attention to maximizing DVB-T reception rather than reliance on the more robust ‘limited edition’ analogue signals).

On the downside, the digital broadcast signals are more fragile (e.g. pixelation & ‘borderline’ decodes can be problematic). The DVB & DAB+ transmitters utilize sharply directional antenna arrays so the crude ‘point-and-shoot’ approach to reception needs refinement. Moreover, in this region, the digital broadcasts are not designed to cover the original analogue reception from the same major site (such as Mount Tamborine). Instead, multiple sites in this region employ Single Frequency Networks (SFN) to provide a backup for those consumers who are in a black spot and cannot get reliable reception from the main site.

The analogue television switch off has meant that a digital signal meter (previously solely the domain of the professional installer) is sometimes necessary. In past, pointing the antenna to the azimuth where the analogue signal was of the highest S/N ratio, the DVB-T signal was often also peaking where the broadcast was from the same site. This is an oversimplification, and assumes the digital (DVB) and analogue (PAL B) share similar transmission parameters. Significant factors such as co-channel interference off the back of the receiving antenna may also come into play.

It cannot be denied that the challenge is considerable. However, there is a wealth of information available to the public. A considerable number of enthusiasts are ‘playing’ with fortuitous & DX DVB-T television, perhaps even more than analogue radio enthusiasts. The rewards are worth it! Thanks to the enthusiastic advice of Ian, Jamie & Leigh VK2KRR, this blog is now able to cover DVB-T reception… stay tuned. With the efforts of the Mobile Muzza in receiving the DAB+ Canberra multiplex from Goulburn it is clear there is some good company to be shared.

The photographs on this blog entry comprise two of the largest antennas suitable for long distance UHF DVB-T & VHF DAB-T reception. By no means are these necessary, these are merely a sample of the extensive range of antennas commercially available for this pursuit.

Further information

Austech Forums

DTV Forum Australia

Free to Air Satellite Forum Asia Pacific

Fellow enthusiasts

Clinton’s Digital TV DX Images

Leigh’s Digital TV DX Images

If you are an active DVB-T enthusiast with a public on-line presence, please comment so your website can be added to the above links!

Armchair propagation indication

Amateur radio operator Leigh Rainbird is using the marine ‘radar’ from ships as a propagation indicator. Leigh says that whilst the vessels’ transponder output is 12 watts, if high gain antennas and low loss coaxial feedline is used these signals get out extremely well.

In essence, the indicators provide real time indication of tropospheric ducting and high MUF sporadic E events.

This blogger has been using the indicators for approximately a week. The substantial variation in the 48 hour tracking distances on-line was positively correlated with tropo seen in the field. Above average conditions on the Port Macquarie, Coffs Harbour & Byron Bay tracking stations were reported at the time of ducting between Taree and this receiving location.

The Hepburn forecasts are invaluable for forecasting tropo, but like any forecast the weather is certainly not guaranteed. Real time propagation indicators help to bridge the gap!

Sounds good? Leigh explains precisely how to do it on the forum of the VK Logger. Please read the instructions then have a play. Perhaps set up your very own AIS receiving station?

Favourite receiving stations

Newcastle

Port Macquarie

Byron Bay

Gold Coast

Further information

Facebook

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.

Eternal damnation at Point Glorious

Today’s task was to travel to Cooloolabin Dam in Queensland’s most-populated South East coastal region. According to the Bonzle Digital Atlas, the dam occupies approximately 160 hectares of land. The signs nearby proclaimed the virtues of a lookout called Point Glorious, situated west of Yandina in the Mapleton National Park.

In all honesty, the hobby of long distance FM reception was not intended to play any part in today’s proceedings. However, since a greater Rockhampton district (Mount Hopeful) powerhouse broadcast was audible in the carpark at the dam, a feat which was entirely unexpected, a trip to Point Glorious seemed like a good option. Cooloolabin Dam’s carpark has an estimated altitude of 301 metres above sea level and is located approximately 21 kilometres from the coastline, according to the Bonzle Digital Atlas. Not bad elevation for a carpark!

Obviously, a lookout respite also provides an opportunity for some pretty pictures to put on the blog. Sure, scantily-clad women would be preferable for many readers. Unfortunately, no willing candidates were found, despite an exhaustive search today, just these photos.

The unsealed road to Point Glorious offers a steep uphill mountain bike ride lasting 45 minutes according to the official guidebook from the Sunshine Coast Council and Tourism Queensland. Unfortunately, the mountain bike was not readily available for the trip. Even if it had been brought along, this blogger’s calves were aching from the treadmill session the night before. The video below documents this trip as undertaken by snake expert Ray Cam 01:

The Dabbler’s Dream™ is kept readily on hand for bush exploration attempts just like a water bottle. Point Glorious lookout is nine kilometres from four 20 kW ABC broadcasters and 15 kilometres from three 20 kW ABC broadcasters. Why so many? For overseas readers, all you need to know is that wasted spectrum and overlapping reception areas are something the publicly-funded ABC broadcaster specializes in!

Where Bundaberg’s rum distillers should have been on the band, loud ABC talk stations occupied the frequencies. In this blogger’s experience, the radio is a write-off 15 kilometres from a major 100 kW broadcast site so this was expected. These Silicon Labs’-based radios are still the king of strong signal performance in the portable world, such that few enthusiasts dare not to own one.

Instead, the factory radio and antenna provided with the vehicle above were called into service. The antenna was a short helical whip design. Typically such designs incorporate a FM pre-amplifier to compensate for the lack of efficiency at the resonant frequency.The Japanese-made factory radio featured Digital Signal Processing much like every modern FM car radio. Selectivity seemed to be roughly the same as the JVC HS-IVi tuner which offers a step up in performance from a conventional radio that usually incorporates 3 x 180 kHz ceramic IF filters. Like fellow blogger Dbrmuz, when confronted with an unfamiliar car radio, one soon realizes how nothing on the market comes close to Blaupunkt’s SHARX IF filter designed for the congested German band. But the phrase ‘any port in a storm’ comes to mind!

Point Glorious lookout has an elevation of 400 metres and predominantly faces northwards. Scribbly gums and grass trees adorn the lookout according to the Queensland Department of Environment and Resource Management. But as athlete Neil Ennis’ photograph above shows, mist and smoke haze may sometimes obscure the view. Travel Journals.net proffers the critical statistics:

A 100 square km area around Point Glorious has an aproximate population of 149,178… and an average elevation of 148 meters above the sea.

2.49 km north east of the Point Glorious lookout is a bloated belly of a mountain called Eerwah which has a sharp peak of 379m above sea level accessible to hikers only. Eerwah is a difficult three hour climb, according to Aussie Bushwalking. 4.06 km south west is another towering beast called Mount Bottle and Glass according to Travel Journals.net. This panorama shows significant obstructions at the lookout from the south-east all the way to the north-west.

Let’s finish with a relaxed bandscan, which was taken in flat conditions according to Mr Hepburn’s prediction, archived below. The bandscan will provide azimuth and distance details so readers can more readily grasp the signal paths involved upon the Sunshine Coast.

The view of this blogger is that any bandscan should be representative of permanent troposcatter reception at a lookout. Please note that a few uncontrollable factors meant that the Point Glorious bandscan was not ideal. Firstly, the stop was hurried, with a maximum of 10 seconds spent listening to each frequency. Secondly, images were present on a number of vacant channels which may have masked the reception of very weak troposcatter or jet-reflected signals. Thirdly, the receiving equipment itself was a limiting factor for the reasons mentioned above. This bandscan was a lot of fun but certainly not an exhaustive scan. Let’s get cracking!

Rockhampton stations (80 kW) were crystal clear to the north-northwest at 389 km. ‘How clear?’ you may ask! Well, here is what News Radio on 105.5 MHz sounded like.

Bundaberg stations (3 kW) were strong from the north at 190 km. Further west, Rebel FM Biggenden (1 kW) was strong at 143 km.

Hervey Bay & Booral stations (500 watts-10 kW) were permanent from the north at 126-132 km. Based on the terrain, it seems likely that Hervey Bay commercial stations are regular reception on the Sunshine Coast.

Southport stations (25-26 kW) were permanent from the south at 167-174 km. These Gold Coast stations can be heard driving around the streets of Maroochydore as long as one is well away from the high-rise strips. High rise attenuates FM signals much like a mountain range does.

Beaudesert stations (200 watts-5 kW) were clear from the south at approximately 155 km. The factory radio permitted easy separation of Breeze FM 92.1 next to local station 91.9 Sea FM, which broadcasts from a site only 33 km away.

Warwick stations (80 kW) were strong from the south-southwest at 250 km. The dam was in that direction which probably would have made this path far easier.

Kingaroy & Wondai stations (5-15 kW) were strong from the west at 103-114 km despite the terrain obstruction in the path.

Portable recordings were undertaken on the Samsung Yepp using 192 kbps constant bitrate MP3 with the internal monophonic microphone. The factory radio was housed inside a 2011 Nissan X-trail, as photographed by Garro 9.2 above. FM Scan was used for all azimuth and distance calculations with the exception of Beaudesert where As the Cocky Flies was used.

Additional photography of this region

Tony Elmer

FM DXing

Neil Paskin

Species

Andy Wizma

Musings on tropo

This is a highly recommended source of information on technical issues which is invaluable for the long distance FM enthusiast:

The VK-VHF mailing list aims to serve the community of radio amateurs and others interested in the technologies and techniques of operating on the amateur bands from 50 MHz and up, with a particular focus on weak-signal or long-distance working and propagation.

Unfortunately, every time a group of enthusiasts get together on a forum or mailing list, politics ensues as every contributor has strongly-held, differing opinions. It’s been my experience that in any given specialty, including my own profession, a small minority of participants have failed to learn the requisite social skills involved in communicating properly in pursuit of purely selfish agendas. This list is no different in that regard. Having being a subscriber since 2009, I am pleased to announce that this list has been largely free of inflated egos for the last twelve months or so.

Let’s get some diverse views on tropo in Australasia…

The Tropo across the Australian bight is interesting. I often take note of that occurrence and then watch it settle across the pond afterwards. Not always, but a good indicator.

Steve ZL1TPH

Of course, to state the bleeding obvious, summer time is best. It is the weather conditions that really determine the propagation – a High nestled in the Bight is a great start but there’s more to it! Wally Howse VK6KZ wrote a great article on the subject:

VHF, UHF & Microwave Propagation & the Great Australian Bight

Dave VK3HZ

I can remember talking with Kerry [Adams VK5SU from Ceduna] at the time about how he could regularly work the guys in Albany and Esperance like locals along the coastal duct, whereas the Adelaide stations would be hearing nothing.

Peter VK3QI

VK-VHF Digest, Vol 48, Issue 10 Feb 2012

It is usually assumed that being on mountain tops will get you further – that is not always the case. Those who have tried to operate along the Great Dividing Range from VK3/VK2/VK4 have often found shielding effects from population centres – it is REALLY difficult to find accessible spots in the Great Dividing range that provide good takeoff in more than one direction.

Quite often one can be too high and miss ducting. We had a documented example the last Summer FD between MtTassie VK3WRE/p and McLaughlin’s Lookout VK3ER/p a distance of 230 kms. Perfect signals (as one would expect) on 1.2, 2.4, 3.4 and 5.7 Ghz but absolutely nil on 10Ghz – (above the duct) – three hours later the duct had lifted and 10Ghz was as good as the lower bands – this is all on video see:

Is a 10 Ghz qso over 200 kms between two mountain tops easier than a 50 km qso between a mountain top and someone in an urban area shielded by buildings etc.? Does the same degree of difficulty apply to lower frequencies where urban obstructions are far less inhibiting?

One of the peculiarities of the Australian continent is the propensity for high pressures to develop and remain stationary over large areas of the continent. Not necessarily just the Great Australian Bight or the Tasman sea. An example of this occured last Summer when a large duct developed over western NSW and north eastern South Auatralia which enabled stations in northern NSW to work across to Adelaide on 1296 for a significant period of time when south of the Great Dividing Range there was limited propagation.

Peter VK3QI

VK-VHF Digest, Vol 40, Issue 15 Jun 2011

Clip Cairns

On November 13th, 2011 tropo occurred to the following places.

Here is tropospheric ducting from FM stereo broadcast 106.7 MHz ABC Local Radio Cairns. These ABC stations broadcast at 100 kilowatts and ducted across the Coral Sea at distance of 1,341 kilometres .

Watch

Audio was encoded via Line In on the portable Degen DE1121 MP3 recorder at the maximum bitrate possible of 128 kbps. In the Americas, this receiver is known as the Kaito KA1121. Clips were split without re-encoding using the free software programme MP3Splt.