BRAZIL VIA ANTARCTICA

Chasing Rádio Saturno

Rádio Saturno is an unlicensed independent broadcaster based in Belo Horizonte, Brazil. We do not know the exact location, and station details are sparse! Operating on both FM and shortwave, it provides a continuous music service and has developed an extensive online presence, including internet streaming and social media.

I have been chasing this station for some time now. Finally, the “propagation gods” looked favourably upon me last night. Here are the notes from my logbook:

6149.96 BRAZIL. R. Saturno - Belo Horizonte, MG. 1005 Pop music and occasional anncts. Easily checked and confirmed via the KiwiSDR in Goiania, Brazil. Pleased to finally hear this after much trying. I first noted a fair-to-weak signal 35 min after sunrise in Belo Horizonte. It faded by 1020. I was expecting the reception to occur earlier in the evening, not this late. Jul 22.

I knew our New Zealand colleagues could regularly hear this station, but I hadn't had any luck until now. So, why would that be? I’m located in the southeastern part of Australia, not that far away from New Zealand. The distance between Belo Horizonte and Mount Evelyn is 13,545 km (8,417 mi). Between Belo and the middle of NZ is approx. 12,200 km (7,580 mi).

So, what gives?

Well, I suspect it has something to do with the Great Circle (GC) track taken by the signal. Compare the two graphics below. Belo is in the south-east of Brazil. Remember, the great-circle path represents the shortest surface route between two points on the Earth and is the reference path normally used when analysing long-distance HF propagation. It’s also a fact that is always in the minds of international airline pilots! 😀 The GC path between Belo and the middle of NZ travels to just below 60 degrees South, into the Sub-Antarctic region.

But the track between Belo and Mt Evelyn runs significantly farther into Antarctic territory. The southernmost portion of the green line dips deeply below the 60°S latitude line. It cuts directly across a significant portion of the white-shaded Antarctic mainland (specifically East Antarctica). While the segments immediately adjacent to Australia and South America cross through the Sub-Antarctic oceanic zone, the apex of the curve crosses directly over the frozen continent itself, making it reasonable to regard this as an Antarctic propagation path. This difference may appear small on a globe, but it places a much greater proportion of the Australia path within high geomagnetic latitudes where HF propagation is considerably more vulnerable to disturbance.

There are several factors that probably explain why Rádio Saturno's signal is difficult to hear at my home QTH. These include increased exposure to auroral absorption, Polar Cap Absorption (PCA), greater geomagnetic sensitivity, and auroral flutter. Although we have passed the peak of Solar Cycle 25, solar and geomagnetic activity remain sufficiently elevated that these effects continue to influence long-distance HF propagation. Let's examine each of these factors in turn:

Exposure to Auroral Absorption: The greatest effect comes from the proximity of the southern auroral oval. Unlike paths confined to mid-latitudes, the Mount Evelyn–Belo Horizonte circuit passes through regions where energetic charged particles from the solar wind are channelled by the Earth's magnetic field into the upper atmosphere. During geomagnetic disturbances, these particles greatly increase ionisation, particularly within the D region, thereby increasing HF absorption. The consequences include increased signal attenuation, reduced signal-to-noise ratio, fading or complete signal disappearance, and higher absorption in the lower HF bands (3–10 MHz). Even moderate geomagnetic storms that have little effect on tropical paths may significantly weaken this Antarctic route.

Polar Cap Absorption (PCA): During strong solar proton events, the Antarctic ionosphere can experience PCA. Although PCA is most commonly discussed for true polar paths (crossing near the poles), long southern paths, southern trans-equatorial paths such as Brazil to southeastern Australia, can still be affected if the signal path traverses the Antarctic ionosphere. Effects include severe attenuation below about 15 MHz and potentially complete loss of propagation on the 31-, 41- and 49-metre bands.

Greater geomagnetic sensitivity: This path is considerably more sensitive to K-index and A-index increases than, for example, Australia-to-Indonesia or Australia-to-Japan. For Antarctic paths, when the planetary K-index rises, fading becomes deeper, the Maximum Usable Frequency (MUF) often falls, and multi-hop F-layer propagation becomes less reliable.

Auroral flutter: If propagation intersects disturbed auroral regions, signals may develop the characteristic auroral flutter familiar to hams and SWLs. Instead of smooth fading, signals become rough, raspy, rapidly fluttering, Doppler spread of a few hertz, and occasionally distorted beyond intelligibility. This is caused by scattering from irregular ionisation within the auroral zone.

Recently, I wrote about these effects on FT8 digital signals in a post entitled STRONG SIGNAL, NO DECODES: Auroral Flutter and the Bouvet-Australia FT8 Puzzle. It’s fascinating stuff!!

But, it’s not all bad news!

The Antarctic portion of the path demonstrates strong seasonal variation. For example, in our current season, which we call the Austral winter, there are longer periods of darkness, lower D-layer absorption, and improved lower-frequency propagation, resulting in excellent opportunities for DXers on 49, 41 and 31 metres.

In addition, nearly the entire path between Belo and Mt Evelyn, and between Belo and NZ, lies over seawater. Seawater is an excellent conductor that enhances the efficiency of low-angle HF skywave propagation by providing favourable launch and arrival conditions compared with most land surfaces. Compared with continental paths, this often results in lower propagation losses, cleaner signal characteristics, and improved multi-hop efficiency. Much of the signal path involves ionospheric hops whose ground reflection points occur over highly conductive seawater.

Predicted Signal Strength Maps

Using the VOACAP SWL web app, we can get an idea of how the Rádio Saturno signal reaches us. However, to construct this map, we have to make some assumptions about the station’s operating circumstances. For example, we don’t know the transmitter output power. I’ve seen it reported as anywhere between 250 watts and 1 kW. We have no idea about the type or height of the antenna being used, or whether it is situated on a hill, a flat area, or in a valley. We don’t know whether the antenna has any directional characteristics and how that might favour the signal in any specific direction. All these factors could make significant differences to the resultant map. So, for the purposes of this exercise, here are my assumptions:

Power: 1 kW

Antenna: Ideal isotropic radiator (0 dBi)

Residential Noise at my QTH: Rural (semi-rural, actually, with fairly low noise most of the time)

Broadcast Quality: Poor (a figure I’m happy to accept as I am not expecting “all 5s” SINPO from this signal. I'm expecting a weak DX signal, not hi-fi!) 😄

In the map below, you can see that Mount Evelyn is right on the fringe of reception when I first tuned in at 1005 UTC, as calculated for July 22, 2026.

Signal Strength map at 1000 UTC between Belo Horizonte and Mount Evelyn on July 22. (Click to see enlarged map)

Below are two maps that provide a closer look at my end of the signal path, showing the differences between 0800 and 1000 UTC. As you can see, at 0800 I would have a slightly higher chance of hearing Rádio Saturno (using the parameters above) than at 1000 UTC. This is because Belo Horizonte has passed its sunrise period and daylight is well established.

Predicted signal at 0800 UTC

Predicted signal at 1000 UTC. By 1020 on July 22, the signal had faded.

OK, so what do we know about Rádio Saturno?

Well, not much, really!

Although Rádio Saturno is widely regarded as an unlicensed broadcaster under Brazilian communications regulations, most international DX publications do not label it a "pirate" station. Recent issues of NASWA Journal, DX Fanzine, Australian DX News (ADXN), and Hard-Core-DX simply list the station as "Rádio Saturno, Belo Horizonte", focusing on frequency, programming, and reception details rather than its legal status. The notable exception is HF Underground, which classifies the station as a Brazilian pirate broadcaster because it focuses specifically on unlicensed radio activity.

In practice, Rádio Saturno operates more like an independent or "free radio" station than a traditional pirate broadcaster. It maintains a continuous music format on both FM (92.3 MHz) and shortwave (6150 kHz), and also offers a professionally designed website, live internet streaming, a social media presence, and an Android app. This combination of full-time broadcasting and digital platforms places it in a growing category of modern Brazilian independent broadcasters that blur the traditional distinction between pirate radio, community radio and licensed commercial broadcasting.

My 2026 winter DX season goal was to hear Rádio Saturno

✅ DONE!

So, what do I do now? Well, if propagation conditions allow, I will be trying for the station any time after 0700 UTC. Under favourable propagation conditions, it should be possible to receive this very low-powered broadcaster for at least four hours during the remaining winter months.

Oh! And one final thing! Rádio Saturno plays a great selection of popular, jazz and world music. I have listened to it many times via remote SDRs and have found its programming most enjoyable.

👉 But the greatest enjoyment comes from tuning into Rádio Saturno using my own radios, antennas and DXing skills. Nothing beats that! 👈

73 and wishing you good DX!

Rob Wagner VK3BVW

Current local time in
Mount Evelyn, Australia

CLICK HERE for VK3BVW Live Stream (Clublog)

QRZ callsign lookup:

Search This Blog

Mount Evelyn DX Report