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I wrote several articles in the past where I refer to innovation in Amateur Radio. This morning a thought came to mind on why is there currently not a satellite with a DMR Transponder (repeater) up in space? I was trying to think "out of the box" and look at ways and means to turn my thoughts into reality, if there is such a possibility.
Thinking "out of the box" is absolutely a great way to approach innovation in amateur radio. Amateur Radio has a rich history of development driven entirely by amateurs experimenting with limited resources and unique constraints.
However, true innovation in this hobby relies on a balance between unconventional thinking and foundational science.
Why Out-of-the-Box Thinking Works
Resourcefulness: Limited power regulations and frequency bands force you to find clever ways to maximize efficiency.
Historical Precedent: Amateurs invented weak-signal digital modes (like FT8) and bounce signals off the moon (EME) because someone asked "what if?"
Cross-Pollination: Bringing concepts from computing, machine learning, or material science into radio often yields breakthrough results.
The Innovation Blueprint in Amateur Radio
To make your creative ideas successful, pair your out-of-the-box thinking with these structured approaches:
Master the Fundamentals: You must understand Maxwell's equations, wave propagation, and circuit design to break the rules effectively.
Identify Real Constraints: True innovation solves a specific problem, such as reducing noise, shrinking antenna size, or bridging communication gaps during disasters.
Iterate and Test: Build prototypes, collect data, and use antenna analyzers or software simulation tools to prove your theories.
Share with the Community: Amateur radio thrives on open-source collaboration. Presenting your ideas on forums, Git repositories, or at club meetings helps refine them.
Prominent Areas Needing Innovation
If you are looking for modern challenges to apply your creativity, focus on these emerging sectors:
AI and Machine Learning: Using neural networks for predictive propagation filtering or automated signal decoding in dense noise.
Alternative Materials: Experimenting with meta materials, fractal geometry, or everyday conductive liquids for stealth antenna designs.
Digital Signal Processing (DSP): Developing open-source algorithms to extract ultra-weak signals from high-noise urban environments.
Green Energy Integration: Creating ultra-efficient, off-grid solar or kinetic power management systems for remote field operations.
Now reading the above my thoughts ran away with me regarding a DMR transponder (repeater / beacon / node / hotspot) payload on a South African satellite. Can it be done and is it possible to communicate using DMR via a satellite? Is there a satellite specifically named "Oscar-DMR 1" in existence or being built in South Africa's space programme or amateur radio history. Currently this type of communications is not possible.
If you are waiting for a homegrown South African satellite or an OSCAR (Orbiting Satellite Carrying Amateur Radio) series spacecraft to launch, here is the factual reality of what has actually happened and what is currently in progress.
The Real South African Satellites
South Africa has already successfully launched multiple satellites. If you are looking for local aerospace achievements "seeing the daylight," they have already made it to space:
SUNSAT (SO-35): Launched in 1999, SUNSAT was South Africa's very first satellite, built by Stellenbosch University. Critically, it carried an amateur radio payload and was officially designated as OSCAR 35 (SO-35) by AMSAT. It saw plenty of daylight before its mission ended.
ZACUBE-1 & ZACUBE-2: Developed by the Cape Peninsula University of Technology (CPUT). ZACUBE-1 (TshepisoSAT) launched in 2013, and ZACUBE-2 launched in 2018.
MDASat-1 Constellation: In January 2022, South Africa successfully launched a three-nanosatellite constellation via a SpaceX Falcon 9 rocket. These operational maritime domain awareness satellites track shipping traffic off the South African coast.
ZS1I created the fictional "DMR 1" Satellite Name
The term DMR stands for Digital Mobile Radio, which is a widely popular land-based digital protocol used by radio enthusiasts and businesses across South Africa.
Terrestrial, Not Space: Amateur radio operators in SA heavily utilize the South Africa DMR Repeater Network. This network relies on ground-based repeater towers, not dedicated South African "DMR satellites."
Conflation with Commercial Satellites: You may be thinking of commercial mobile satellite services or push-to-talk satellite radios that interface with DMR-style dispatch systems on the ground.
Future South African Space Missions
If you are wondering about the next major government-backed leap into orbit, the Department of Science and Innovation has active plans:
National Communication Satellite: The government has been exploring multi-billion-rand plans to acquire or launch a dedicated communications satellite to bridge the digital divide and reduce reliance on international space entities. However this look like a very "far in the future" project with many logistical and financial issues to first solve.
Deep Space Ground Tracking: While not a satellite itself, South Africa broke ground on a massive, state-of-the-art Deep-Space Ground Station in Matjiesfontein (Karoo), built in partnership with NASA to track future lunar missions.
Sadly you cannot work DMR (Digital Mobile Radio) directly through orbiting amateur radio satellites. Hopefully by means of innovation in technology my thought on building such is satellite is not far fetched and will not forever just be a thought. In South Africa building such a satellite will be problematic but that is a topic for another time.
Let's see why this can or cannot currently be implemented.
You can absolutely build a physical DMR repeater and launch it into orbit on a satellite. However, doing so introduces a severe physics and timing challenge that standard DMR protocols are not designed to handle.
The core issue is the speed of light and the Doppler effect.
The Timing Problem (TDMA Breakdown)
DMR relies on TDMA (Time Division Multiple Access). It divides a single frequency channel into two distinct time slots (Slot 1 and Slot 2).
The Rule: Each radio must transmit in an incredibly precise window—exactly 30 milliseconds long.
The Margin: The standard protocol only accounts for standard terrestrial distances, leaving a guard timing buffer of about 1.25 milliseconds to handle propagation delay.
When a satellite is orbiting overhead (even a Low Earth Orbit, or LEO satellite at ~500 km), the distance from the ground station to the spacecraft changes continuously and rapidly. Because the radio waves must travel hundreds of kilometers to space and back, the propagation delay exceeds that 1.25 ms guard window.
Consequently, your radio's packet arrives late, shifts out of its slot, and bleeds into the adjacent time slot. This completely breaks the synchronization, causing the repeater's onboard computer to reject the handshake.
The Frequency Problem (Doppler Shift)
DMR uses 4FSK digital modulation. It relies on precisely mapping four distinct, narrow frequency shifts to represent binary data.
Because a LEO satellite travels at roughly 27,000 km/h, the frequency shifts dramatically as it approaches and moves away from you. This Doppler shift warps the digital signal. While a human ear can decode an uncorrected analog FM signal through a bit of static, a digital DMR modem will see the warped 4FSK signal as corrupted gibberish and refuse to decode it.
How to Make a Space-DMR Repeater Work
If an amateur radio group or space agency wanted to make a true DMR satellite work, they would have to implement one of two workarounds:
Modify the Radio Firmware (Software Solution)
The ground station's DMR radio would need custom firmware capable of predicting the satellite's exact orbit. The radio would then have to continuously alter its timing (transmit early or late to hit the slot perfectly) and automatically adjust its frequency to cancel out the Doppler shift in real-time.Put the Spacecraft in a Geostationary Orbit (Hardware Solution)
If you put the DMR repeater on a geostationary satellite (35,786 km above Earth), the satellite remains stationary relative to the ground. This eliminates the Doppler shift entirely. While the time delay would be much larger, it would be constant, allowing engineers to build custom terrestrial radios with a massive, fixed timing buffer specifically for space.
Consolation Prize
There is currently a "consolation prize" on how you can use your DMR Radio to connect to satellites indirectly.
You can use your DMR radio to connect to satellites indirectly by talking through an MMDVM hotspot (or a local digital repeater) connected to the internet. From there, your signal is routed to space through a commercial geostationary satellite (such as QO-100) using an up/down converter, a dish, and an SDR (Software Defined Radio).
Unlikely that a dedicated amateur satellite named "Oscar - DMR 1" will be built in South Africa
It is highly unlikely that a dedicated amateur satellite named "Oscar - DMR 1" will be built specifically for standard DMR voice communications in South Africa. While amateur radio organizations like AMSAT constantly develop new spacecraft, standard commercial DMR protocol is fundamentally incompatible with the physics of Low Earth Orbit (LEO) satellites.
The Geostationary Exception, there is hope!!
The only way a true DMR transponder could work in space is on a Geostationary (GEO) satellite like QO-100. Because GEO satellites remain completely stationary relative to the Earth's surface, there is zero Doppler shift or changing propagation delay. While there is no official "Oscar - DMR 1" payload planned, experimental digital voice links are routinely tested via GEO transponders using specialized ground stations. More on this in a future article once I put on my "out of the box" and "innovation" hat.
Was this article a waste of time? NO definitely not. I now have more questions than answers that I will be looking into.
ED. This article was compiled by ZS1I with the assistance of AI.
