V5/N7BHC : Troposhperic Ducting from Namibia

The primary purpose of the Tropo operation on the expedition is to study and test trans-oceanic tropospheric ducting using on VHF and UHF across the South Atlantic Ocean. The results and conclusions are to be shared with the amateur radio community. A secondary purpose is to increase interest and activity in the region and worldwide in long range trans-oceanic VHF communications.

Critical Success Factors
A number of factors need to be achieved in order to consider the research and operation to be fully successful. These include the items below.
  • Communicate on 2m from Luderitz Bay to St. Helena and Ascension Islands.
  • Communicate on 2m from Luderitz Bay to the South America mainland.  
  • Successfully receive FM broadcast stations from South America. 
  • Gather data on weather conditions at the time of successful communications.

Operational overview
Tropospheric ducting spanning long trans-oceanic paths has not been fully explored. Several regions are already well proven. Some of these have been worked for more than 5 decades, while others are more recently “discovered”. These established paths are:
  • California to Hawaii
  • The Australian Bight
  • West coast of Europe down West coast of North Africa
  • Reunion Island to South Africa
Other trans-oceanic ducts have long been suspected. Occasional reports of DX reception over very long oceanic paths have been reported over several paths.  Probably the main reason these paths have not been worked yet is the lack of operators interested in and equipped to work these paths in the optimum locations.  Some of the paths yet to be worked include:
  • North Atlantic     
    • North America to West Africa
    • North America to Europe
  • South Atlantic    
    • Southern Africa to South America
    • Southern Africa to St. Helena and Ascension Islands
  • South Indian Ocean   
    • Reunion/ Mauritius to Australia
    • South Africa to Australia
  • North Indian Ocean  
    •  Africa to India or Indonesia
This expedition will explore the South Atlantic paths in more detail. The data gathered from reception reports in early 2008 proved the existence of temperature inversions between Southern Africa and St. Helena and Ascension Islands, as well as from Ascension Island to Brazil. The earlier reception reports included frequent reception of mainland FM broadcast stations on the Islands, and the reception of marine band signals on 156 MHz. By early November 2008, listeners on St. Helena have started reporting FM stations from Brazil and Angola, and 156 MHz marine radio from Walvis Bay in Namibia.

The research project from Luderitz Bay in January 2009 will use a number of different radio systems to fully explore the South Atlantic ducts. These will include FM broadcast band monitoring, as well as 144 MHz and 432 MHz high erp stations operated as breakable beacons for the duration of the DXpedition. A separate station will also be configured for 2m FM using vertically polarized yagis.

Propagation Mechanism
The primary propagation mechanism for trans-oceanic ducting is the subsidence temperature inversion. There is a lot of detail available on the Internet on this propagation mode, and will not be repeated here. The reader is encouraged to review the following articles on the web.

V5/N7BHC Tropospheric Equipment Lineup
Communications research and attempts will be made on several frequencies and modes. Primary operation will be on 2m SSB, CW, and Digital modes. Secondary modes will be 2m FM and 70cm SSB, CW, and Digital. In addition, the commercial FM broadcast band will be actively scanned. FM radio stations make excellent beacons in the absence of ham radio band beacons. These lists below list the planned equipment lineup, and are subject to change as plans evolve.

144 MHz SSB / CW / Digital
The primary operating band will be 2m SSB, CW, and Digital modes.
  • Transceivers. The primary radio will be a Yaesu FT-847. This radio is equipped with INRAD 2.1 kHz SSB and 400 Hz CW filters, and a 2.6 kHz Collins mechanical filter. An Icom IC-7000 will be the secondary radio.
  • Amplifier. A TE Systems 375 watt amplifier is to be the primary 2m power amplifier. The amplifier will be modified to include continuous fan cooling. An rfConcepts MaxAmp 45 will be available as a backup amplifier.
  • Audio Interface. A SignalLink USB will provide the audio interfacing for digital modes
  • Antennas. A number of antennas will be used.  Horizontal polarization will be the main polarity used.
    • The primary rotatable yagi is a M2 2m18XXX yagi. It will be horizontally polarized.
    • A 51 element fixed rope ladder yagi, also horizontally polarized, will be used for the longest planned path to NE Brazil.  It has 20.5 dBd gain before ground gain. 
    • The FM yagis, two stacked 11 element WA5VJB yagis, can also be selected for 2m DX.
  • Mast.  To be determined. Possibly a shared mast for the 2m SSB, 70cm SSB, and 2m FM vertical yagis. Minimum height 10m.
  • Feedline. LDF4-50A or similar 1/2" hardline of required length.
  • Filter. Possibly a 2m bandpass, 70cm reject filter to keep 2m out of eth 70cm recevie. A Microwave Module MMt-200-7 is a possible candidate.
  • Coax Switch. SDDT to select either large yagi.
  • Power Supply. An Astron linear supply will provide the primary power for this station.

432 MHz SSB / CW / Digital
Both the primary and secondary radios have 70cm, it makes sense to add 70cm capability. In addition, tropo ducts sometimes favor 70cm over 2m.
  • Transceivers. A Yaesu FT-847 will be the primary radio, with an Icom IC-7000 as the secondary radio
  • Amplifier.  A TE Systems 175 watt amplifier will be modified to include continuous fan cooling.
  • Antenna.  4 x 13 element yagi array, horizontally polarized, rotatable. This will be the EME antenna, switched to tropo use when 70cm EME is not active.
  • Mast. To be determined.  Minimum height 8m.
  • Feedline. LDF4-50A or similar 1/2" hardline of required length..
  • Power Supply. An Astron linear supply will provide the primary power for this station.

144 MHz FM
The goal is to have simplex contacts with distant stations. Although SSB, CW, or Digital stations offer improved weak signal performance over FM, there are many more 2m FM equipped stations and repeaters than the weak signal mode stations. Therefore a station needs to be set up to support contacts with FM equipped stations on simplex and repeater operation.
  • Transceiver. It would be ideal to have a dedicated FM mobile radio with 50 watts output for scanning the repeater bands. The radio would be borrowed in South Africa. Alternatively, the IC-7000 or FT-847 can be used.
  • Amplifier. rfConcepts MaxAmp45 170 watts output.
  • Antennas. A pair of vertically polarized stacked short yagis, 11 elements each, designed by WA5VJB. The power divider will use simple ¼ λ 75Ω coax sections. The advantage of using the stacked yagis is that they can be mounted on the same mast as the FM broadcast yagi, and not have to worry about unbalanced wind and weight loading, or metal going up through the element plane. If a wooden mast is used, a longer single yagi could be used with feedlines all routed to the rear.
  • Mast. Rotatable, possible shared with FM broadcast antenna. Minimum 7m height.
  • Feedline. LMR-400 as required.
  • Power Supply. An Astron linear supply will provide the primary power for this station.

FM Broadcast Band
FM Broadcast signals make excellent beacons. They are numerous and in many locations. The Luderitz Bay site has only four low power FM transmitters in the area so local interference should be minimal. The yagi antenna will have good side and rear lobe suppression, further reducing interference.
  • Receivers.  The primary FM Broadcast antenna for the expedition will be a Sony HD radio with RDS. The new  Sony XDR-S10HDIP having incorporates the tuner of the smaller Sony XDR-F1HD and includes an amplifier and speakers. The secondary receiver will be the Icom IC-7000.
  •  Antenna. A yagi with good broadband performance across the 88-108 MHz spectrum is desired.  An eight element log-periodic design from Cebik is a good compromise between size and gain. It offers good broadband performance, and very low side and rear lobes. The antenna has been fabricated entirely in the US for testing, but will be shipped over minus the boom to save on size and weight. A new boom will be fabricated in South Africa. The antenna will either be switchable between horizontal and vertical polarization, or mounted at a 45º slant polarization so it will be 3dB down to either horizontal or vertical FM stations.
  • Mast.  At least 5m tall. Can be hand rotated. The antenna will be primarily fixed on a 300º bearing. This mast will probably be shared with the 2m FM vertically polarized antenna.
  • Feedline.  The antenna is fed with RG6QS with F connectors on both ends. An F-female to UHF-male adapter is needed for the IC-7000.

A computer is required for a number of reasons. It provides the modem for digital modes, a CW and Voice memory keyer, and logging. It also provides communications to the outside world for scheduling contacts, checking propagation, and time synchronization.
  • Computer. PC based laptop. Dell 9100 which I already have.
  • Second monitor. Used to display more data simultaneously, borrowed in South Africa.
  • Audio Interface. SignalLink USB with cables for eth FT-847 and IC-7000.
  • Serial ports. USB/RS-232 adapter, with RS232 cables
  • Software.  Ham Radio Deluxe, DM780, WSJT, CW Skimmer, Audio Recorder, Spectran, UDY-2, Voice Key Express, NMEA Time, AREPS
  • Networking. Wired network around the compound. Broadband Internet access will be provided via 3G service from mtc Namibia, The USB 3G module will route access to all PCs at teh statioj via a Dovado UMR Router.
  • Surge Protector. A high quality surge protector should be used at least for the computers, if not the entire station.

 V5/N7BHC Tropo Operating Plan
Operation from V5/N7BHC on tropo will be multiple faceted. In addition, care has to be taken to coexist with the EME station at the same site.
  • Beacon Calling. The 2m and 70cm stations will operate as beacons, or call CQ continually. The 70cm operation will utilize the 70cm EME antenna array. EME operation on 70cm is expected to be be limited to 2-3 days, so the tropo station on 70cm should be active much of the time. A CW beacon could use either an external keyer such as the ID-O-Matic, a PC based keyer such as DM780, or an internal memory keyer in the radio. Continual digital mode calling would be with WSJT, or could be under control of DM780. Voice keying would use a voice keyer internal to the radio, or PC based software such as UDY-2 or Voice Key Express.
  • Listening Period. The beacon mode will have a receiving period to listen for responding stations. It will also lower the duty cycle and keep the radio systems cooler.
  • Monitor and scan FM bands.  The FM receiver will be used to listen for Saint FM on St. Helena Islands and mainland South American stations. FM stations can serve as numerous VHF beacons. The Sony receiver has 20 memory channels, or can be used in scan mode. It does not unfortunately have frequency lockout to scan over the local Luderitz stations. The IC-7000, if used, has 5 bands of 99 memories, and can scan an entire bank, It also has band-edge scan.
  • Checking repeaters. The FM station will be sued to scan for and work FM repeaters on vertical polarization. A list of Brazilian and African repeaters will be programmed into the radio. A special temporary authority has been requested to allow the use of the 146-148 MHz frequency range in South America for the duration on the DXpedition.
  • Operating modes.  The primary operations mode will be JT65B to take advantage of the enhanced weak-signal performance. CW, SSB, and FM will also be used.
  • Coordinate transmission with EME station. The EME station will potentially be operating for 12-13 hours every day. The EME stations using JT65B will always transmit the first period, and listen on the second period. The tropo station in CQ and beacon modes will operate on the same minute sequence as the EME station to avoid mutual interference when the EME station is in operation. 
  • Posted Frequencies. Frequencies for tropo calling and monitoring will be confirmed to the web after arrival in Luderitz Bay. Planned frequencies and modes are:
    • 144,299.2: CW/SSB: CQ V5 and all DX, Horizontal
    • 144,29.2: JT65-B/SSB/CW: CQ V5, Horizontal
    • 144,350, 145.500 FM and repeaters: CQ V5,  Vertical
    • 432,100: CW/SSB: CQ V5 and all DX,  Horizontal
    • 432,150: JT65-B/SSB/CW: CQ V,  Horizontal
  • Work all modes. Significant paths should be worked on all possible modes such as SSB, CW, FM, and digital modes to establish band/mode records.
  • Work all bands. Stations should be asked if they have other bands such as 70cm and 23cm, and worked on those bands if possible.
  • Schedules with DX stations. Advance schedules can be arranged with DX stations well in advance or on the spot through Internet pages like ping-jockey or email and Skype.
  • Email and Phone contact. Special email addresses and Skype addresses need to be established for the DXpedition. These need to be monitored 24/7 during the expedition.
  • Monitor and collect Hepburn and weather data. Weather data should be gathered to correlate successful VHF ducting with weather conditions.  The information that should be gathered ever six hours, and at the time of any significant QSOs, is:   
    • Hepburn maps
    • Isobaric weather maps
    • Sea surface temperature
    • Inversion data at Luderitz, St. Helena and Ascension Islands, and Brazil coast.
  • Record QSOs. Significant contacts should be recorded on audio for later conformation and analysis. Recording should be accomplished on a PC, and saved in either MP3 or WAV format. Time code recording is desirable on the audio track.
  • On-line log. Logging of all QSOs should be uploaded to Internet as close to real time as possible.
  • Website. A website shall be created to post DXpedition information. A copy of all pertinent data such as frequencies and schedules need to be posted to the website.
  • Blog. A blog of station activities will be helpful to stimulate interest and convey news, events, and operation status.

Collaborative stations
Several people have been identified as strong collaborators. They will listen for and attempt to work V5/N7BHC on various bands. They will also listen for and log other amateur and broadcast stations.
  • St. Helena and Ascension Islands
    • SWL          IH74db           John Palmer, St. Helena
    • ZD7VC      IH74db           Bruce Salt, St. Helena
    • ZD8I          II22tb              Ian Coverdale, Ascension Island
  • Brazil
    • PY2ZX      GG66nt           Flavio Archangelo, Jundiai, Brazil
    • PY2BJO    GG65-HH22  Junior Torres de Castro, maritime mobile between South Bahia and Recife, Brazil
    • PY6/PY2ENO   HH18FC        Enos Emerick, expedition to Conde, Bahia (PP6), Brazil by Japy DX Group
    • PY2REK    GC65pu        Joao Komuves, Itanhaém, on the shore of Sao Paulo
    • PY5XX      GG53qw        Peter Sprengel, Itapoa, Brazil
  • Argentina
    • LU1CGB   GF05om         Adrian Sinclair
    • LU7FIA      FF97qa          Willy Viola, Rosario, Argentina
    • LT1F          FF97              Bad Power Antenna Farm, Rosario, Argentina
  • Southern Africa
    • ZS1TX       JF96hd          Chris Muller, Cape Town
    • V51JN       JG77gh          Swakopmund. Beacon on 144.450
Flavio PY2ZX has been very helpful in spreading the word in South America. Consequently, many stations will be looking for signals from Namibia. Several are making specialexpeditions to the NE coast of Brazil to coincde with the V5 expedition, hopefully positioning themselves in an ideal location.  Flavio has helped tremendously by translating much of this web page into Portuguese. He has added additional material of interest.

So the general home page with all links:
For Brazilian partner transatlantic by the Japy DX group.
Namibia Expedition translations to Portuguese, Page 1 and  Page 2.

Additional Data Sources