Mount Evelyn DX Report: A LOOK AT RADIO MADAGASIKARA

A LOOK AT

RADIO MADAGASIKARA

Here is an interesting observation of winter propagation on the circuit between Madagascar and southeastern Australia, specifically my home at Mount Evelyn. We are hearing Radio Madagasikara on the recently revitalised 6135 kHz before 10:50 pm local eastern Australian time, something that would not happen regularly in the summer months here. It is a good example of the difference between winter and summer reception conditions. Here's my log entry from last night:

6135 MADAGASCAR. R. Madagasikara - Ambohidrano. Thanks to a tip-off from Craig Seager and Matt Francis. Local East African music at 1257, ID at 1300, then into a long commentary/report in the Malagasy language. Many mentions of Madagascar and Malagasy. A local popular song by a female singer and a chorus of backup singers at 1323. Into more commercial Afro pops at 1330. ID at 1400 and news. Monitored to past 1415 with a fair to good signal, July 9.

Below is a map of the great circle path between Madagascar and Mount Evelyn from last night, July 9 at 1300 UTC. You notice that the majority of the path is in darkness, which is important if a signal on a lower frequency is to propagate over long distances.

So, on 6135 kHz at 1300, there is every prospect that reception is possible on this path.....and, of course, we have last night's log to prove that is the case! Let's also look at the VOACAP circuit reliability chart for last night, which shows a 54% reliability that the signal will get through on that frequency at that time.

The chart tells us the percentage of days in the month when the actual SNR (Signal-to-Noise Ratio) value will equal to or exceed the REQ.SNR. (Required Signal-to-Noise Ratio). This is just one of a number of parameters we can use to check when reception may be possible on a specific circuit.

Now, let's take a look at the same circuit during the opposing six month period i.e. high summer in the southern hemisphere:

This is the great circle path on January 9 at 1300 UTC. More than half the path is in daylight, which on 6135 kHz will be an issue because of higher signal absorption in the ionosphere over the daylight parts of the circuit as well as higher noise levels at that frequency during that time of the year. And, indeed, the circuit reliability chart tells us exactly this with a reliability factor of only 8% of the signal making it through to Mount Evelyn on that frequency at 1300 UTC in the southern hemisphere's summer season.

Comparing the two charts, we can see that there is a difference of one hour between winter and summer circuit reliability reaching 90% on that frequency.

Current reception of Radio Madagasikara is also helped by the fact that the channel is clear of other stations at that time. And, in my log, I mention the tip I received from Craig Seager and Matt Francis, both who live further up the eastern seaboard state of New South Wales. Both DXers were also receiving Radio Madagasikara at fair to good levels at their localities.

73 and good DX to you all!

Rob Wagner VK3BVW