In the last few months, there has been talk on the Amateur Radio media channels about something called 'Polar Modulation'. A lot of what is presented is quite technical so in this post, I'll give a very basic overview of what 'Polar Modulation' is and why it might be a game changer for Amateur Radio.
First of all and to make things clear, 'Polar Modulation' is NOT another mode like AM (Amplitude Modulation) or FM (Frequency Modulation). Polar Modulation refers to how a radio transmitter operates in a newer and more efficient method.
Linear Amplifiers... Let's look at how the final power amplifier in a typical amateur radio transceiver operates.
With modes like CW (morse code), the signal is just one single carrier frequency and the amplifier can be non-linear. With SSB (voice) and FT8 (data) modes, there are multiple frequencies involved and there is the potential for these frequencies to mix in the amplification stage resulting in a distorted signal and splatter across the band. To prevent this distortion, the output stage must be as linear as possible.
This linearity however comes at a cost and that is in terms of efficiency. A typical amateur radio transceiver with an output stage running Class AB might have an efficiency of about 55%.
In other words, to give an output of 100-watts on SSB, the output stage might require something like 190-watts of DC power from the power supply.
This means that roughly 90-watts of power in the form of heat needs to be dissipated in a large heatsink in the radio which in turn uses a cooling fan to reduce the temperature.
This inefficiency obviously doesn't scale well. As the output power goes up then more heat needs to be dissipated with larger heatsinks and cooling fans.
Polar Modulation... A radio using 'Polar Modulation' uses a completely different method to generate an output signal.
With a linear amplifier, the output transistors are partially on which generates a lot of heat. In contrast, non-linear amplifiers using Polar Modulation generate less heat because the output transistors are used more like very fast switches.
These can be turned on and off hard at RF frequencies and are made to saturate resulting in a very low resistance when they're on which means a lot less heat is generated. Efficiencies in the region of 90% can be achieved.
To avoid the signal becoming distorted, the audio signal from the user is first digitised and is split up into amplitude and phase components. These signals are then used to modulate the power supply to the RF amplifier which then generates the SSB signal. This is no simple feat and requires quite an amount of processing power and complexity within the radio.
Polar Modulation Implementation... While Polar Modulation has been used in transmitters in the commercial world for some time, it's only recently that the technology is becoming available in the amateur radio market.
Flex Radio... Back in March of 2017, Tony Brock-Fisher, K1KP co-authored an article in QEX titled 'The Polar Explorer - You may never look at your “linear amplifer” the same way again.'
That article goes into a lot more detail about what Polar Modulation is and you can read the PDF document HERE
That project by K1EP eventually formed the basis of the new Aurora radio which was released by Flex Radio in 2025. This radio implements Polar Modulation in the transmitter and has a power output of 500-watts.
This is from the promo material for the Aurora from Flex Radio...
"This radio boasts 80% efficiency, thanks to its use of polar modulation and high-efficiency transmitter architecture. Legacy linear amps often run around 40-60%, so this design cuts waste heat by 70-80%.
What does 80% efficiency mean in practical terms? It means that out of every 100 watts of supply power drawn from the wall, about 80 watts go to your actual RF signal, and only 20 watts are lost as heat. That’s a major improvement over typical HF rigs and amps.
Polar modulation is a highly efficient signal transmission technique that separates a radio frequency (RF) signal into two fundamental components: amplitude (envelope) and phase (angle) components, allowing each to be amplified independently and more efficiently.
Unlike legacy linear amplification methods, which require power-hungry and heat-intensive amplifiers to preserve signal integrity, polar modulation enables the use of switching-mode amplifiers (such as Class D, E, or F) that operate with significantly higher efficiency."
The new Flex Radio Aurora range is certainly at the upper end of the amateur radio market with prices ranging from $6200 - $9,600 in the US (€7000 - €10,500 in Europe and £6200 - £9600 in the UK).
The main thing here is not to get side lined on the issue of price but to take note that it is the first implementation of Polar Modulation by one of the big amateur radio manufacturers.
QRPLabs... Hans Summers, G0UPL of QRPLabs has implemented his own version of Polar Modulation called 'Envelope Elimination and Restoration (EER)' in his QMX product.
This QRP radio with its 5-watt output power is certainly at the other end of the price spectrum in terms of cost with an assembled price of under $200. Info... https://qrp-labs.com/qmxp.html
Video 1 - Hans gave a presentation of the QMX product at the RSGB convention in October of 2025. You can find the live stream link HERE
Look at the video from 4:29:27 to 5:13:30
Video 2 - This is another clip titled 'RSGB 2025 Convention polar modulation: Hans Summers G0UPL, Mike Walker VA3MW, Stewart Bryant G3YSX'. Link HERE
Implications of Polar Modulation for Amateur Radio???
1) Size - One obvious attraction is that the increased efficiency means that smaller heatsinks can be installed in a typical 100-watt amateur radio transceiver which means the radio could shrink in size. This is a potential cost saving for manufacturers.
2) Power - The alternative of course is that the size and heatsinks stay the same but the newer models can be made to operate at higher powers like 150-watts giving the radios featuring Polar Modulation a competitive edge over 100-watts radios not using the technology.
3) Shortage of parts - If in the future enough companies implement Polar Modulation in their transmitter designs then there will be less demand for the high power transistors used in the traditional RF linear amplifiers. If the demand drops too much then transistor manufacturers could stop making those type of devices. Is there a potential that all radio transmitters will end up migrating to the use of Polar Modulation because of a shortage of parts in the supply chain?
Downsides of Polar Modulation???
1) Complexity - While some radio amateurs may build their own radios with linear RF outputs, it's hard to imagine many would be able to design or implement their own version of radio using Polar Modulation.
2) Dirty signals? - If a transmitter using Polar Modulation isn't designed properly, the transmitted signal may have high phase noise with increased power in the higher order intermodulation products.
This means wider signals, splattering across a band and causing interference to other users.
This can be mitigated by using fast digital signal processing techniques in the radio but what happens if some manufacturer tries to save costs and implements a poor design?
Imagine a radio using Polar Modulation running 100-watts on the HF bands with the quality and performance of a Boafeng UV5R handheld?
In conclusion... I've tried to give a brief and simplified overview of the current state of affairs as regards to Polar Modulation and where things are going.
This technology has the potential to be a game changer in that we may see over time a wholescale redesign of modern amateur radio transceivers.
Even if you're not that interested in what goes on inside of the radio, you should be aware of the potential pitfalls of this technology if not implemented properly.
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