February 28, 2005

Brazil to Barbados on 144MHz....

Congratulations to the JAPY Dx Group for the recent VHF expedition. The write up is excellent and audio's are available too. The detail and audios are proof enough of a genuine communication at 144MHz over a 4400km path.

I do think this is fascinating as it is apparently quite a different experience to TEP as reported in Europe....

The contact was via FM modulation and many FM broadcasts were also heard. From the audio's there seems to be no noticable frequency modulation of the received signal, this appears to be very much unlike the well reported southern Europe to Southern Africa path reported by EA6VQ I discussed (via Skype ) this contact with IK0BZY who personally experienced a major TEP opening in 1989 over a 7000km path to South Africa. The contact was possible only by CW due to the FM and AM nature of the channel distortion.

I also find the contact interesting as the group set out to look for TEP, had just a few days, the solar cycle and time of the year were far from what is considered "optimum" by traditional TEP understanding and yet they made it, it seems it might be quite a reliable channel!.

The path does seem from the map to be symmetrical about the geomagnetic equator as expected for TEP. Looking at the Broadcast log a large number of the stations reported seem to be from Barbados i.e. just one TINY island in the Carribean. TEP or Es may also produce this effect. I am sure many VHF ops have experieced sporadic E openings where the same station appears to be strong for a long time with sometimes no other stations heard.

The FM contact is also interesting as the Barbados station was mobile (was his antenna a vertical whip?) I have sent 8P6JB an e-mail so I hope he can provide a perspective from the Barbados side. Enrico IK0BZY was convinced that when he was working South Africa, that the signal strength was good enough for CW with modest power and reasonable yagi but no way it would have supported 12kHz bandwidth and omni antennas. I guess that this may be explained by the lack of FM distortion.

I guess all of the differences between these contacts and the Europe to South Africa contacts can be explained if shorter TEP paths experience far less FM distortion hence stronger signals in narrow bandwidths....not much 144MHz activity in Central Africa to test this theory though!!

Anyway, I'm very impressed and I hope more tests will now be made. Listen to the audio's on JAPY site, I know if it had been me I would have sounded much more excited!!

Posted by Tim at 05:43 PM | Comments (1)

February 15, 2005

The 156MHz Blog...

Moved up in frequency due to nil activity on 144MHz just for the day. I tried to hear the R/T from B+Q as Ellen Macarthur arrived back in Falmouth after her round the world solo record trip. Maritime comms are NBFM, 25kHz channel spacing, vertical polarisation from 156MHz to 160MHz'ish. I didn't get anything definitively from B+Q but the maritime band was full of comms from the flotilla of small craft following her in, I guess they were all a bit excited as the language was surprisingly anglo-saxon, several "B" words, "C", "F" and even a "Y" word in just half an hours listening as the boats full of photographers jostled for position, it was just like listening the London 2m repeaters. Life boat and Helo were in the area just in case of accidents.

Ellen with flares 2.JPG

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In a fantastic acheivment Ellen sailed around the World in 71 days, just a few minutes sleep at a time, survived huge storms in the southern ocean and set a new World Record time, now I have plenty of air miles from travelling myself and I am no fan of airplanes but this girl must really hate flying.

Posted by Tim at 03:40 PM | Comments (0)

February 02, 2005

I'm still here...

A few pictures of the the new antennas being constructed starring Steve G0CUH doing the energetic stuff whilst I operate the warm, dry digger....Thanks Steve.

Muddy1.JPG

Muddy2.JPG

A few days later after the concrete dried......

Aerial1.JPG

Aerial2.JPG

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No pictures of the tower upright because after 1 month it has only been up a couple of hours due to high winds and no conditions, roll on summer. I will post some pictures of the finished construction later.

On the tower are 2x16ele by I0JXX stacked at 3m apart, a power combiner then PA3CSG low-pass filter to stop the local airfield radar hitting the pre-amp FET, the change-over relay then MGF1801 Cavity preamp by VE3KH, finally followed by a 4 pole DCI bandpass filter. The overall result is very pleasing with a noticable drop in clicks, pops and low level birdies (I thought were computer interferance but which must have been intermods).


I was pleased to receive this QSL for 144MHz today...

Vatican HV0A Comp4.JPG

HV0A Reverse Comp4.JPG

Finally,

I Have recently installed Skype (Voice over IP broadband telephone) on the Shack PC and I am very impressed, free phone calls at amazing audio quality. It is like having the other person in the room with you! I look forward to listening in the the other end of Sporadic-E openings real-time in the summer!

Tim.


Posted by Tim at 09:30 PM | Comments (3)