6474km TEP contact on 144 MHz from Argentina to a ship off the coast of Florida - 9th Dec 2024

Over the last few years, I've reported on many Trans-Equatorial Propagation (TEP) contacts from South America to the Caribbean on the 144 MHz band... links on my 144 MHz page.

For this mode of propagation at 144 MHz, signals must generally cross the Geomagnetic Equator at right angles. This usually means that stations in the south of Brazil work places like Guadeloupe, St Martin & Puerto Rico. Stations near Buenos Aires in Argentina work stations in Curacao & the Dominican Republic.

There has been a distinct lack of 144 MHz TEP openings further west in South America mainly due to a lack of stations at one or both ends of the paths.

So it was a really big surprise to hear that Carlos, LU7MC in the west of Argentina managed to complete a contact with Yuri, UT1FG/MM on a ship to the north of Cuba!

The contact was made using the Q65B mode on the 9th of December 2024 at 01:34 UTC. This is just after 20:00 local time for both stations which is about the peak time for evening type TEP.

The distance was in the region of 6474 kms which is exceptionally long for a 144 MHz TEP contact for South America.

The map above shows just how close UT1FG/MM  was to the Florida. His ship was just 80kms south of the road going to Key West and about 170kms south of Miami.

It's hard to know for certain but I suspect that the TEP signal from LU7MC almost certainly reached Florida. It was most likely that there was nobody active there and looking.

Mode of Propagation... As indicated already, the mode of propagation was TEP - Trans-Equatorial Propagation. There may have been an extension at the northern end of the circuit with some marine tropo / ducting north of Cuba.

Mode of contact... The Q65B mode was used for this 144 MHz contact. The screen shot from LU7MC is shown below...

As you can see below, the signal level was about 0dB to -8dB which is probably too weak for SSB but should be strong enough to be heard by ear and a CW contact would be possible.

The screen shot from UT1FG/MM is shown below...

The signal levels were about the same at -4dB to -8dB.

Equipment... Carlos, LU7MC is located in the city of Mendoza in grid locator square FF57OB. He was running 100-watts into an array of 4 x 10-element Yagi antennas.

Yuri, UT1FG works on a commercial ship and was Maritime Mobile between Cuba and Florida in grid locator EL94PC. He was running 200-watts into a single 7-element Yagi antenna.

In conclusion... This really was an important contact on the 144 MHz band because it shows that there is a very good possibility of a TEP path from the west of Argentina to Florida. Could it extend even further north to some of the other southern US states by tropo? Could the stations in Chile get in on the action?

The really big question is if anyone in the United States is paying attention and is going to try and make a contact?

Link...
a) For more information on long distance 2m contacts, see my 144 MHz page.

5100km TEP opening on 432 MHz from Argentina to Venezuela - February 1978

While openings via TEP (Trans-Equatorial Propagation) on the 144 MHz band seem to be relatively common in South America, it's a different story on the higher frequencies.

While there have been verified TEP openings at 432 MHz in Africa in the past, any reports of TEP openings on the 70cms band seem to be extremely rare.

Back on the 13th of February 1978, YV5ZZ in Venezuela reported hearing LU3AAT in Argentina on '432.1 MHz'. The distance was approximately 5,100kms.

I'm not sure of the exact locations of either stations but Buenos Aires to Caracas is about 5,100kms and seems to be the right distance.

I found two accounts about this remarkable reception reports.

Article 1) The first one appeared in the Amateur Communications column, Electronics Today International from May 1978.

"Evening-type TEP extended to 432 MHz?

Recent record-breakng contacts on the 144 MHz band apparently supported by evening-type (or Class II) trans-equatorial propagation between Australia and Japan, Puerto Rico and South America, have been hot news in amateur circles amongst those who are keen on VHF/UHF DX.

However, no sooner was the upper frequency limit of Class II TEP extended to 144 MHz, previously established as being in the 100 MHz region, than evidence of the possible extension of this ionospheric propagation mode even higher in frequency - to 432 MHz - has come to hand.

YV5ZZ, located in Venezuala, is reported to have heard an Argentinian station, LU3AAT on 432.1 MHz in February during an opening when Argentinian stations were heard working Caribbean stations and stations in the northern countries of South America.

However, two way contact was not established, but this seems only a matter of time."

Article 2) The second one appeared in an article titled 'A Newly Discovered Mode of VHF Propagation [1978]' from the QST magazine dated October 1978.

"On February 13, 1978, YV5ZZ heard weak but identifiable signals from LU3AAT, on 432.1 MHz. Two-meter and 432 propagation far exceeds the capability of the TE mode YV5ZZ was using his satellite antenna system, which is steerable in azimuth and elevation. In the direction of LU3AAT, his horizon is obstructed by a range of mountains. The lowest elevation angle which allows for clearance of the mountain range is 8 degrees. 

On February 16, 1978, YV6ASU heard LU3AAT on 432 MHz, with his antenna at about the same angle of elevation. On yet another occasion, KV4FZ heard LU3AAT on 145.1 MHz. He reported that a peak in signal strength occurred when the antenna elevation angle was 8-10 degrees. This geometry suggests that single-hop F-layer reflection isn’t involved. The angle also seems high for the tilt associated with TE."

Analysis... In preparing this post, I did a search for the first 432 MHz contact with Trans-Equatorial Propagation (TEP) in South America and much to my surprise, I couldn't find anything. Despite the 1978 article saying that a 70cms contact would only be a 'matter of time', it looks as if it never happened and has yet to happen.

This raises the point that I have made in previous TEP related posts... Is there anyone in South America trying to make TEP contacts on 432 MHz??

I see many reports of TEP contacts at 144 MHz made by LU, PY, CX & ZP stations in South America and that's fine. But I think radio amateurs should also be experimenting to see what is possible, to try something new and to push the limits.

The chart about shows the progression of sunspot numbers since 1965. In 1978, the levels aren't that much higher than they are now in the Spring of 2023 and 1978 was also about two years before the peak of solar cycle 21.

Doppler... TEP propagation is well known for it's distortion of the signal due to some spreading. The higher the frequency, the higher the distortion.

I'm assuming that the distortion at 432 MHz will mean that modes like FT8, FT4 and Q65b cannot be used? But is that a correct assumption?

If nothing else, the use of modern weak signal modes will allow a weak signal to be seen on a screen even if it can't be decoded. A sign that a CW contact might be possible if only the signal was a bit stronger.

In conclusion... If anyone has any information about previous TEP contacts on 432 MHz from South America then  please let me know. If not, perhaps someone would like to try for the first 432 MHz TEP contact from South America?

Acknowledgement... Thanks to Carlos, LU7MC for sending on the Electronics Today International article. If your first language is Spanish and you're reading this post via Google Translate then send your information to LU7FC if it's easier.

Link...
1) For examples of TEP contacts on 2m, see my 144 MHz page.
2) For examples of other long distance contacts on 70cms, see my 432 MHz page.