Dave N7BHC (Also PJ4VHF & ZR2BI) left a comment on a post recently about VHF propagation in the South Atlantic. There was so much interesting info in it that I have put it up here as a guest post. There is plenty in there as food for thought.
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Back in 2007-2010, I was trying to drum up trans-Atlantic tropo ducting interest. I am very pleased to see more progress now. A contact from ZD7 (St.Helena Is) to PY (Brazil) on 144 MHz (2m) is 100% probable.
I introduced John Turner at Saint FM, the local FM radio station, back in 2008-2010 to tropo ducting on the FM broadcasting band. He successfully logged many Angolan, Namibian, and Cape Town FM stations. One December he emailed that he was unsuccessful identifying an Angolan FM radio station as he had interference from a Brazilian station on the same frequency. This was using just a car radio with its whip antenna.
Back in March 2008, ZD8I on Ascension Island reported that they sometimes heard Cape Town Marine Radio (ZSC) on 156.8 MHz FM. That is an omni antenna to an omni antenna on FM at a range of 4400 km.
ZD8S on Ascension Island reports listening to Brazilian FM stations with indoor portable radios.
Since then, I spent the next ten years on Bonaire as PJ4VHF. My biggest tropo ducting success across the North Atlantic was the initial reception of D4C/b on the Cape Verde Islands at a range of 4,694km. I strongly encourage any stations on ZD7 and ZD8 to be active on both 2m and 70cm.
I have been studying trans-ocenic ducting for many decades (I started out as ZR2BI in East London). The South Atlantic may be the BEST location worldwide for long-haul ducting, both for range and how often the openings occur. FM vertical polarization works well bit SSB or FT8 on horizontal is even better.
Maybe someday we may be allowed to and able to travel again, and I can afford to visit ZD7 in person. Until then, all I can do is strongly encourage others.
73, Dave N7BHC/PJ4VHF/ZR2BI dpedersen AT drasticom DOT com