Adaptive Pre-Distortion for older Flex 6000 series

Gord-VA7GP

I am curious about the actual realization of APD for the older Flex 6000 series radios…

Purportedly, APD will (now) be an external add-on, due to lower processing-power in the 6000 family.

And here is my Q for today:

Will this external box include a Sampler?

Many amps these days include a sampler-port (perhaps -55dB or -60dB from the Antenna output). Older amps do not. I wonder, then, if Flex may offer a sampler as a accessory for the APD accessory 🤣

Would older amp-owners be advised to find Black Friday sales on Samplers 🤣 or write a note to Santa 🤣

Trucker

The 6000 radios already have a internal feedback loop for the radio itself. But, no external connection to use with an amplifier. Flex Radio has had Adaptive Pre-Destortion working on the 6000 radios in the past. It may be necessary to do some hardware modification to support an external feedback loop for a amplifier. Whether or not Flex Radio will invest the resources to add the ability to do APD, is unknown. I would think it would depend on actual demand and how much money is involved to get it going. And if customers with a 6000 radio are willing to spend the money to get APD with a external amplifier.

James

WD5GWY

Mike-VA3MW

The 6000 radios do not have an internal sampler unfortunately, and an external sampler will be required even for 100 watts.

Gord-VA7GP

OK - but I was wondering if the external computation-box (for the Flex 6000 family) would have this sampler built-in? Or, would both an external-computation-box AND ALSO a sampler be needed?

Not judging 😀 just seeking info to plan a path forward into enjoying APD.

And here is my next Q for today: When?

Mike-VA3MW

At this time, we have not walked it through a full project plan for the cost of manufacturing hardware, required software development time, etc.

Trucker

Mike, Gerald stated on the Community several years ago that Flex Radio has Adaptive Pre-Destortion working with the 6000 radios and that the necessary connections in the radio was already present. He said at the time that Flex Radio did not have enough demand/requests, for ADP to implement it. So, are you saying that the owner and founder of the company doesn't know what he was talking about? An internal feedback loop of some sort has to exist to provide the necessary information for proper correction of the transmitted signal to reduce harmonics. I have also had the same conversation with one of Flex Radio's developers in the past saying essentially the same thing that the connections are there and it has been working on a test bench. It is the fact that there is no external connection to accommodate feedback from an amplifier that is missing in the older radios.

James

WD5GWY

Mike-VA3MW

Yes, he did. However, that is not the case and it has been confirmed with me by Engineering. I am not at liberty to provide the details (above my pay grade as they say). :)

FlexRadio apologizes for any confusion.

Trucker

Explain this from the CTO Stephen Hicks:

Steve - N5AC, VP Engineering

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Official Response

When we designed the FLEX-6000 we had adaptive predistortion in mind so we included a tap from the transmitter that feeds back into the receiver. This gives us simultaneous access to the desired and actual transmit spectrum in the FPGA so that we can implement linearizarion. We also have sensors for temperature, voltage and load match of the PA as these can be used to improve linearizarion. The work that needs to be done for the FLEX-6000 is to experiment with algorithms and input sources to determine what gets us the most **** for the buck and then finalize the implementation.

The FLEX-6000 already has the highest precision DAC of any amateur transmitter and excellent IMD numbers so we decided to focus first on features that the community is waiting for and return later for implementation of predistortion. Predistortion in the cellular business is critical because they are putting many carriers in a single PA and spectral purity when you're doing this is critical. But for ham radio, it is more of a "nice to have" and "nice neighbor" sort of thing -- it's not going to prevent someone from copying YOUR signal and the FLEX-6000 spectral purity is well above the legal limits. Barring significant hype that makes this a marketing issue, we'll look into this after finishing the items on the road map that you, our customers, have told us are important for you.

Since we thought ahead, you will not need to use an external device to tap the actual transmit signal and feed it back into the receiver when the time comes. Incidentally, our VP/GM of our government business, Graham KE9H, has considerable experience with predistortion having run a company that focused on predistortion in cellular PAs. He also developed PAs for HPSDR.