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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.
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The Polar Explorer © 2025 transmitter is so efficient because it replaces legacy linear amplification with switch-mode amplification — specifically Class D amplifiers — and leverages digital signal processing (DSP) to separate and handle the signal’s envelope (amplitude) and phase components independently.
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The transmitter is extremely efficient, which results in the need for a much smaller heat sink. The reduced heat sink size and transmitter all fit inside the same space as a traditional 100W amplifier.
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SmartSignal is included with all Aurora models.
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This doesn’t include the 500W transmitter and associated power supply, right?
It does. Because of the high efficiency of the Aurora transmitter, a small power supply, a small heat sink, and the transmitter all fit into a compact space. The Aurora radio has it all: receiver, 500W transmitter, and AC to DC supply!
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I checked, and my current radio is about 40-50% efficient. This means I’m saving about half the power, with Aurora, right?
Actually, no! The math around efficiency is a little more complex. A 100W transmitter that is 40% efficient generates 150W of heat (100/0.4 = 250W of input power. 250W – 100W output = 150W of heat). A 100W transmitter at 80% efficiency generates only 25W of heat (100/0.8 = 125W. 125W – 100W output = 25W).
The heat generation of the 80% efficient transmitter is only 17% of that of the 40% efficient amplifier. This is a 6x reduction in the heat generated! This allowed FlexRadio to put a 500W transmitter in the space of a 100W linear amplifier!
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Yes!
Always monitor temperature and follow the manufacturer’s duty-cycle recommendations. The Aurora transceivers are rated for Intermittent Commercial and Amateur Service (ICAS), which is 25-50% duty cycle.
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We have tested 100% transmission for a continuous 2 hours. While we do not recommend doing that, we are confident in how robust this transceiver is.
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Unfortunately, you cannot. The Polar Explorer technology that Aurora is built upon requires inputs not of low-level composite RF like a legacy amplifier, but of an RF carrier and an envelope waveform. No radios on the market output these components, expecting an external transmitter that uses polar modulation.
The Aurora transmitter must be tightly integrated with the host transceiver. Therefore, this is available only as a FlexRadio integrated transceiver.
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Absolutely — Aurora models are built on the same amazing remote platform that all FLEX-8000 series radios are built on. The same API, with extensions for Aurora, is available as well as SmartLink capabilities. Aurora is the perfect high-power remote HF hardware.
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An internal antenna matching unit capable of matching up to an SWR of 3:1 is a standard feature. The core Aurora technology is more sensitive to impedance mismatches than a linear amplifier.
As a result, all Aurora models come with an integrated tuner to ensure the impedance presented to the transmitter is close to 50Ω. Use of the integrated tuner will be required for any non-resonant antennas.
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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.
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.
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The AU-510 is built on a FLEX-8400 with ATU design, so it has one internal Spectral Capture Unit (SCU), whereas the AU-520 is built on the FLEX-8600 design, so it contains two SCUs and competition-grade preselectors.
As a result, the AU-510 has four (4) antenna connectors (two that can output 500W), has two internal receivers, and can place those receivers on one antenna at a time.
The AU-520 has six antenna connectors (two that can output 500W), has four internal receivers, and can place those receivers on either of two antennas at the same time.
See comparison chart for more info!
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The most obvious addition if you have a 100W radio is an increase in power to 500W. In addition to this, the Aurora radios are 80% efficient, so the electricity required to make 500W is less than half of what it would be with a traditional radio and an external amplifier.
As a result, you save on operating costs. Also, since the heat generated is about one-fifth to one-sixth that of a legacy 500W amplifier, it lowers cooling requirements on your house and can help keep an even temperature in your shack.
Finally, because Aurora is completely integrated, your shack with Aurora is much cleaner with fewer wires, cabling, and devices.
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What would the Aurora buy me?
The input power required for a legacy 500W linear amplifier is 1,000-1,250W to make that 500W output. This is on top of the 100W radio sending power to the amplifier, which will draw around 250W during transmit.
This means your legacy 500W amplifier set up would need 1,250–1,500W of input power to make that 500W output. Aurora needs 650-700W of input power to make 500W of output power. On top of that, a legacy 100W/500W configuration weighs about 47 pounds. Compare that to the 18-pound Aurora transceiver!
That’s a more than 50% reduction in input power and a 62% reduction in weight for a 500% increase in power output! Aurora also eliminates all the cabling to connect a legacy 500W station together.
Finally, if you’re using a generator, solar or any other off-grid power system, the system itself can be significantly smaller or use less fuel.
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Yes!
DXpeditions are fraught with logistical challenges. Aurora provides a 500W transmit capability in an 18-pound integrated radio that uses half the electricity (and therefore fuel) of a legacy 500W configuration.
Aurora is a 500W station that can literally be put inside a carry-on bag. The advantages are similar to the POTA discussion above, but cannot be underestimated for a DXpedition.
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Not at all.
With far less heat being generated, cooling requirements are dramatically reduced. It still includes active cooling, but it’s much quieter and more compact than you might expect for 500W output.
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Yes. Less waste heat means your shack stays cooler, especially important for smaller or poorly ventilated rooms.
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Generally, yes. Less thermal stress on components leads to longer life, fewer thermal shutdowns, and overall more stable performance during long operating sessions.
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No. This transmitter is designed strictly for the amateur bands and the hardware is not capable of transmission outside of normal amateur HF/6m bands.
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The radio can operate from 100 to 240VAC thanks to its autosensing built-in AC power supply, allowing it to deliver its full power. This means that for those operators with only 120VAC line voltage, the radio can still develop 100% of its maximum output.
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No. You must use 80 to 264 VAC as a supply voltage.
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The maximum power on 6m is 200 watts.
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Yes, the ATU is included in every model that handles up to a 3:1 SWR.
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All Aurora transceivers include an integrated 3:1 500W tuner. An external tuner can be used instead if preferred.
Note that the tuner needs to be capable of at least a 500W input and care should always be taken when dealing with high-power RF.
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Yes, you can — but proceed with caution.
It’s critical to avoid overdriving the connected amplifier. Doing so can cause serious damage, not just to the external amplifier but also to the transmitter inside the radio itself. This may impact your radio and amplifier warranty.
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AU-510: $6,199.00
AU-510M: $7,349.00
AU-520: $8,599.00
AU-520M: $9,599.00
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The Aurora radio line is currently in field testing and the first production run has been ordered. FlexRadio is taking deposits for the first production run which we expect to be available in 4Q25.
Orders that exceed the first production run will be moved into the second production run which will be available after 4Q 2025.
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Not at this time.
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Yes, the broad feature set offered in the FLEX-8000 series is also provided in all Aurora radios. The AU-510 is essentially a FLEX-8400 with an 500W Aurora transmitter and the AU-520 is a FLEX-8600 with an Aurora transmitter.
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Yes, transverters can be attached to the XVTR ports in the same fashion as the FLEX-6000 and FLEX-8000 series.
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Yes, and no.
There are certain times of the day and year that you can talk to another person in another part of the world. It depends on many things, such as the radio frequency you are using, the time of the day and what part of the sunspot cycle we are in.
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The number of sunspots observed on the “surface” of the Sun varies from year to year. This rise and fall in sunspot counts varies in a cyclical way; the length of the cycle is around eleven years on average. The cyclical variation in sunspot counts, discovered in 1843 by the amateur German astronomer Samuel Heinrich Schwabe, is called “the Sunspot Cycle”.
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SDR or Software Defined Radio is a radio communication system where components that have been traditionally implemented in hardware (e.g. mixers, filters, amplifiers, modulators/demodulators, detectors, etc.) are instead implemented by means of software on a personal computer or embedded system.[1] While the concept of SDR is not new, the rapidly evolving capabilities of digital electronics render practical many processes which were once only theoretically possible.
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There are many different theories:
The word “HAM” as applied to 1908 was the station CALL of the first amateur wireless station operated by some amateurs of the Harvard Radio Club. They were Albert S. Hyman, Bob Almy, and Poogie Murray. At first they called their station “HYMAN-ALMY-MURRAY”. Tapping out such a long name in code soon became tiresome and called for a revision. They changed it to “HY-AL-MY”, using the first two letters of each of their names. Early in 1901 some confusion resulted between signal from amateur wireless station “HY-ALMU” and a Mexican ship named “HYALMO”. They then decided to use only the first letter of each name and the station CALL became “HAM”.
In the early pioneer days of unregulated radio amateur operators picked their own frequency and call letters. Then as now, some amateurs had better signals than commercial stations. The resulting interference came to the attention of congressional committees in Washington and Congress gave much time to proposed legislation designed to critically limit amateur radio activity.
More can be found on Wikipedia.
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FlexRadio’s have our SmartLink utility which is included for free with any of our FLEX-6000 series radios. This allows you to ‘connect’ to your radio from any part of the world and allows today’s Ham Radio Operator to make contacts while they are away from their hamshack.
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Licensed amateur radio operators receive a call sign from their country’s communications agency (the FCC in the United States), and are required to identify themselves at regular intervals on the air. Not identifying is a sure sign of an unlicensed operator.
Ham Radio Operators and the FCC (in the US) do routinely use direction-finding techniques to find these stations (called Pirates) and then report them to the authorities.
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Amateur Radio is regulated by the Federal Communications Commission (FCC) under the Communications Act of 1934. It is also subject to numerous international agreements. All Amateur Radio operators must be licensed. In the U.S., there are three license classes. The higher the class of license, the more frequencies are available. Earning each higher class license requires passing a more difficult examination. Although regulated by the FCC, license exams are given by volunteer groups of Amateur Radio operators. Operating under organizations called Volunteer Examiner Coordinators, volunteers administer and grade tests and report results to the FCC, which then issues the license. U.S. licenses are good for 10 years before renewal, and anyone may hold one except a representative of a foreign government.
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Today’s ham radio operator has many choices when it comes to purchasing an HF radio that covers from 160M to 6M and 100 watts RF output power. A new FLEX-6400 can be purchased for just over $2000 US for customers in the United States. Our radios come with a 2 year warranty and a 30 day return policy.
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The FlexRadio Tuner Genius XL is a plug-and-play amateur radio tuner developed by 4O3A and marketed by FlexRadio Systems. It is available in a 1 x 3 or SO2R antenna switching configuration. Not only does it work with FlexRadio’s it can also be integrated with OEM radios from Icom, Kenwood, Yaesu, and Elecraft. Unlike the HF Tuner from Palstar (HF Auto) with mechanical tuning which can be very slow, the Tuner genius XL can be tuned to memorized frequencies well less than 1 second.
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The FlexRadio Power Genius XL Amplifier is the most versatile HF amplifier available. It is able to product full legal limit and does it very efficiently. It can be connected to other OEM radios from Icom such as the IC-7610 and IC-7300, Kenwood, Yaesu and Elecraft. The Power Genius XL is a perfect plug in for any SO2R contest station. The Power Genius XL works well in any remote HF configuration.
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The FLEX-6000 series radios are the best for FT-8 operation. They provide the ability to copy very weak signals in the FT-8 / FT-4 passband that are right beside very strong signals. This is something that is very difficult to do in most other Super Heterodyne HF radios. FLEX-6000 series radios will allow you to make more contacts, find new countries and increase your award count.
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There are many great HF radios available today. The FLEX-6000 series provides much more feature/functionality with the built-in remote operation, Ethernet connectivity, CESSB for 3db more RF power out and an amazing set of receivers that will enhance any ham radio operators operations today.
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multiFLEX is a unique feature offering to FlexRadio transceivers that affords the operator the following benefits:
- The ability to use multiple clients simultaneously at one location
- Reduced station costs for contesters
- Enhances remote operation capabilities
- Allow the radio to be remotely shared with a second user
For more details go to flexradio.com/multiFLEX
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Yes. Switching between SmartSDR versions is an easy process. Due to the changes to the database in v3, you will want to do a factory reset and import your saved settings if you do choose to downgrade from v3.
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Each FLEX-6000 Series radio comes from the factory with a license of the current major version of SmartSDR (ie v1, v2, v3). Subsequent point releases are included at no additional cost to the owner (ie v2.1, 2.2, 2.3). When the next major version is released it will be an optional paid upgrade. Should the user choose not to upgrade, their current version will continue to work in perpetuity.
A user may also skip versions should they choose. A user can upgrade from v1 to v3 with a single purchase.
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Given your buddies permission, absolutely! Note that the licensing is enforced on the radio side, so anyone with permission and access to a v3 licensed radio can try it.
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You can expect the bandwidth to be about the same as it was in SmartSDR v2 for the same number of resources (Panadapters, Slices, DAX channels, etc.). Obviously, with more than one client available, it may mean that more of those resources are in use at any given time.
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Yes. USB Cables will work with multiFLEX. The settings are generally related to the radio, depending on the source selection. Some sources may not be as useful in a multiple client scenario since more than one client could impact the USB Cable band/frequency (e.g. Active Slice). When a source is used, like a particular RX Antenna, the last Slice using that antenna to change frequency will trigger the USB Cable to update (last one wins).
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Most likely, yes. Many of our API developers have already been working prior to launch to support SmartSDR v3.0 in their software. Please check with the individual developer of your program of interest to find out where they are in that process for details. 3rd party applications that depend on SmartSDR CAT will work at launch.
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Yes. SmartSDR CAT and DAX will allow the operator to bind to a particular Station to help identify which SmartSDR GUI client to follow (e.g. SmartSDR for Windows, SmartSDR for Maestro, etc.)
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Yes. The PowerGenius XL is an ideal amplifier to use with SmartSDR with multiFLEX. The integration showing the power output directly in the display and the ability to instantly switch to barefoot all from the SmartSDR screen makes it a breeze to operate. Other amplifiers will also work with multiFLEX provided that they can switch in an appropriate time (~10ms) or an appropriate delay is added to compensate for any switching delays (as would be customary for typical operation).
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The TX indicator will return to say TX Ready in the lower right (reference the screenshot below).
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The transmitter operates on a “first come, first served” basis. So the first client to transmit gets control of the transmitter until they un-key. When your client is transmitting, you will see the familiar TX indicator in the lower right on SmartSDR for Windows. When a client other than your own is transmitting, an indicator such as the one shown in the screenshot below with inverted colors will be show to draw attention to the fact that the radio is in transmit mode by another client. You can hover over the indicator to get information about which Station is transmitting.
It looks like this when your client is transmitting:
It looks like this when a different client is transmitting:
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Each SmartSDR client will have an associated Station name. On a PC for example, the Station Name will default to PC. The Station Name can easily be changed to something else more descriptive by the operator. The Station Name will be used as a means to identify which client you want to associate with for other applications like SmartSDR CAT and DAX. This gives the appropriate context to run the radio in the presence of multiple operators.
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See answer about CAT/DAX support here. First, understand the Station Name concept. This is key to how CAT and DAX work with multiFLEX.
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No. Since each Slice is unique and specific to each client, they are handled independently.
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No. Each client will call the first Slice opened Slice A. Then Slice B, etc. The radio model determines how many Slice (receiver) resources are available (6700: 8, 6500/6600/6600M: 4, 6400/6300: 2)
When no more resources (Slices, Panadapters, DAX Channels, etc) are available, the client will indicate this to the user by disabling the button to open more of that resource.
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Yes. With multiFLEX you can mix and match any SmartSDR client including SmartSDR for Windows, SmartSDR for Maestro, SmartSDR for M models and SmartSDR for iOS.
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Limited Edition owners were entitled to a free upgrade of v2 of SmartSDR. V3 is the first paid release for Limited Edition owners.
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multiFLEX will allow two operators to connect to the radio simultaneously. The two operators will be able to split the resources available on the radio. For a FLEX-6400, since there are two panadapters and two receivers available, each operator can have access to one panadapter and one receiver.
On the FLEX-6700, for example, the operators will be able to split the eight receivers and panadapters between the two operators. So if one operator wants to work DX on two bands, using two total panadapters and a receiver on the DX station on each band and a receiver in the pile-up, he would use two panadapters and four receivers. This would leave up to six panadapters and four receivers for the second operator. In a bulleted format:
Operator 1: 2 Panadapters, 4 receivers
Operator 2: 6 Panadapters, 4 receiversThese panadapters and receivers can be placed on the same or different antennas, depending on whether the radio has one or two SCUs.
The radio resources break down as follows:
FLEX-6300, FLEX-6400: 2 panadapters, 2 receivers (one antenna at a time)
FLEX-6500: 4 panadapters, 4 receivers (one antenna at a time)
FLEX-6600: 4 panadapters, 4 receivers (two antennas at a time)
FLEX-6700: 8 panadapters, 8 receivers (two antennas at a time) -
Yes, users do not need to be physically present with the radio to access it. With SmartLink remote the two users can be anywhere as long as there is a network to support it.
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Given that each radio only has one transmitter it is not possible for two users to transmit at the same time. Transmit priority is given on a first one wins basis.
Each radio has a number of specific number antennas that the radio can support simultaneously. This is the number of Spectral Capture Units (SCUs) in the radio. There is one SCU in the FLEX-6300, FLEX-6400 and FLEX-6500 and two in the FLEX-6600 and FLEX-6700. If you have two operators on a single-SCU radio, they would each need to use the same antenna, but could use different bands (provided the antenna works on both bands). For the dual-SCU radios, each operator can be on a different antenna — or they could share antennas. For example, on a FLEX-6600 or FLEX-6700, operator one could be listening on 20m (beam on ANT1) and transmitting on 40m (dipole), while operator two is doing the opposite (listening on 40m and transmitting on 20m).
If you have a single antenna that is wide-banded, for example a Tennadyne T10, and say a beverage, both operators could have the T10 as their transmit and receive antenna (single SCU) or one/both could transmit on the T10 and listen on the beverage.
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No, not at this time. In the initial release of multiFLEX the clients will act independently giving the impression of two completely separate radios. This means that tuning a VFO on Maestro will not tune the VFO on SmartSDR on Windows.
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Yes. With the new SmartControl feature that is available in the latest version of SmartSDR v3, you can control a FLEX-6000 using a Maestro while also operating the radio with SmartSDR for Windows.
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Yes. One of the key benefits of this feature is to allow Multi-Single contesting with one radio. By using SmartLink remote, the operators do not need to be physically present with the radio. This also cuts the radio requirement in half for Multi-2 and Multi-Multi contest stations!
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Yes, we will be releasing SmartSDR v2.5 later in 2019. SmartSDR v2.5 will be a maintenance release which will include a number of performance improvements and bug fixes.
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This is not necessary, you may purchase and install SmartSDR v3 as a direct upgrade from version 1, and you will also automatically get all of the additional features release in v2 over the last 18 months with no additional charge.
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No, this is an optional one time purchase for all SmartSDR v3.x versions. Should you not find the features in SmartSDR v3 to be of value, you can continue using your current version or purchase at anytime during the release cycle when a point release provides you something of interest/value. Your current version of SmartSDR will continue to operate in perpetuity.
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Download the latest software from our website and follow the installation procedure. The radio will automatically acquire the license if it is connected to the internet. Please note, if your radio is directly connected to your PC then it does not have an internet connection. For best results, connect your radio to your home router.
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multiFLEX can have two users connected simultaneously. This may also occur using a SmartLink connection. If both parties wish to connect to the radio over SmartLink remote they will need to share a single login.
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SmartSDR v3 comes with multiFLEX allowing a mix of up to two devices (PC, Maestro™, iPad®, or iPhone®) to connect to the radio simultaneously and in both cases can use all the resources of the radio.
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If you purchased your radio or SmartSDR v2 on or after Oct. 1, 2018 no additional payment is required. If you purchased a FLEX-6000 series radio prior to Oct. 1, 2018 there is a $199 fee (U.S.) to upgrade to this latest major version release. All subsequent point releases (v3.x) are available at no additional expense.
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SmartSDR v3.0 is expected to be available by mid April 2019.
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- New Band Settings menu/panel that allows a user to visually set certain settings per-band ( power levels, TX Inhibit, ACC/TX1/TX2/TX3 Enabled, RCA/ACC TX Request Enable and HWALC)
- TX/MIC Profile Changes – all settings are now saved on-the-fly (as settings are changed).
- Various performance improvements and bug fixes
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The main feature in this release is called multiFLEXTM. multiFLEX allows a FLEX-6000 series radio to have two clients connected simultaneously (PC, Maestro™, iPad®, or iPhone®).
For more details go to flexradio.com/multiFLEX
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SmartSDR is the term used to describe the software that powers the FLEX-6000 series radios. SmartSDR v3.0 is the next major release of SmartSDR for all FLEX-6000 series radios