FlexRadio Aurora 500W HF Radio

Mike-VA3MW · May 17

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What is Aurora?

FlexRadio has developed a new HF transceiver with a 500W output on 160-10m HF bands (200W on 6m). This radio does not use a legacy RF exciter followed by a linear amplifier. Instead, it uses a transmitter that employs Polar Modulation (PM). With PM, the radio still generates traditional SSB, CW, FT-8, RTTY, and all the standard on-air signals.

A 500-watt transceiver with an integrated automatic antenna tuner (ATU) in a single unit offers a few clear advantages, especially for seasoned operators who value simplicity and efficiency. First, it reduces the need for interconnecting multiple devices, which cuts down on cabling, potential RFI issues, and the complexity of station setup. This integration can also streamline operations, as the ATU and amplifier are designed to work in harmony, often offering faster tuning and better protection for both the radio and the amplifier. Another big plus is the space-saving aspect—ideal for both compact home stations and portable setups where minimizing gear is a priority

Aurora provides significant benefits over transceivers with linear amplifiers. The polar modulation technique (details below) is significantly more efficient than linear amplification. This change to the transmitter yields significant power savings, generates less heat, resulting in the need for a much smaller heat sink, which also reduces size and weight. It is the most significant advancement in amateur radio transmitter technology in the last 50 years.

By adopting the proven architecture of the FLEX-6000 and FLEX-8000 series and maintaining compatibility with SmartSDR, Aurora offers a familiar yet powerful upgrade path for today’s FlexRadio operators.

Introduction to Polar Modulation:

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.

Originally proposed in the 1950s by Leonard Kahn through his Envelope Elimination and Restoration (EER) technique, polar modulation has seen renewed interest with modern digital signal processing (DSP) capabilities.

It offers a compelling path forward for amateur radio, enabling cleaner, smaller, and more energy-efficient transmitters that challenge the long-standing dominance of legacy linear amplifier designs.

Nick · May 30

This is an interesting idea. I wonder if there are any plans to offer polar modulation in a traditional 100 watt radio like the 6/8000 radios. The liter weight and all in one box is great for portable operation, but 500 watts is lite for the regular old rag-chew and contest types and overkill for driving an amplifier.

Just thinking,

Mark_WS7M · May 30

I'm personally very tempted. I operate almost 100% CW and Digital, rarely voice. I have 6400/6600 and a pair of TGXLs and PGXLs and really don't ever op above 350 to 500 watts. Seems like an ideal way to dump a few tuners and amps and radios.

N8VY · May 31

I have an Elecraft K3 and Collins 30L-1 amplifier. I am exploring using AU-520 for my next level. I sure hope delivery is before I pass away (78yo) LOL. My station is near lots of noise sources (modem/router/ 24 channel switch/RAID drive/two PCs/electronic work bench). Moving to closet where antennas come in would greatly help with noise by operating remote. I think that would do wonders for my hearing the weak ones.