Very long distance contacts in the region of 5000-6000 kms on 144 MHz from the Caribbean to the south of Brazil, Uruguay and the area near Buenos Aires in Argentina are reasonably common via TEP (Trans-Equatorial Propagation).
The geometry is just right for these contacts ...a) Population centres at each end of the path with active amateur radio stations ...and b) At right angles to the Geomagnetic Equator.
This map from the 2nd of February 2022 shows a typical opening...
All the paths tend to be parallel to each other as they cross the Geomagnetic Equator at 90 degrees. However even in the example above, you can see a few paths that are not exactly parallel.
LU7MC... Carlos, LU7MC is in the west of Argentina and active on 144 MHz for many years. His location is shown on the map at the top of the post in the far west of Argentina. For Carlos, the other end of his usual TEP path falls in areas further west in the Caribbean around Jamaica and Cuba, areas where there is very little 144 MHz activity.
Carlos writes..."I always wondered the same thing, why no TEP? Many years ago my interest in VHF DX awoke and I began to investigate. I believe that one of the main obstacles is the small number of operators who, are unaware of TEP and miss out on the opportunity to experiment with the different types of propagation at 144 MHz and higher.
After a long time of trying (13 years) it finally happened!! A TEP contact from the west of South America on 144 MHz : LU7MC - HI3I Q65B 5827Km, Very atypical conditions where the strict Trans Equatorial propagation theory seems not to apply. It was always thought that it would occur with stations further west in the Caribbean."
As Carlos writes, it does seem to have been an unusual TEP opening where the path was not quite a right angles to the Geomagnetic Equator.
It also shows that location is everything for TEP... someone near Buenos Aires can almost make daily 144 MHz contacts on TEP with the Caribbean at certain times of year and someone in the west of Argentina has to wait 13 years!
Carlos sent on a few images. This one shows the predicted map of the critical frequency of the ionosphere around the time of the TEP opening. Notice the less intense zone over the Geomagnetic Equator in South America and the more intense region either side which sets up the perfect conditions for a TEP opening.
This screenshot from Carlos shows that the contact was made on 144.180 MHz using the Q65B weak signal mode. Signals are in the region of -12 to -14dB which is just about detectable to the human ear. A CW contact would be very difficult at this signal level.
Note that the time is in UTC. Evening time TEP usually peaks around 8pm local time.
This final image shows the solar conditions on the left with the Solar Flux at 138 and the K index at 1.7. The right hand side of the image shows the confirmation of the contact via LOTW (Logbook of the World).
Chile (CE) ??? ...Now that there has been a successful TEP contact on 144 MHz from the west of Argentina, what about Chile? Is TEP possible from Santiago? Are there any stations in the west of the Caribbean interested in 144 MHz?
220 MHz and 432 MHz??? ...I would be interested to hear of any TEP openings at 220 MHz or 432 MHz. Will the distortion make digital weak signals modes unusable at the higher frequencies?
Thanks for Carlos, LU7MC for the above information and congratulations on your FB TEP QSO.
1) For more TEP contacts, check out my 144 MHz page HERE
