Rob Sherwood (PreDistortion) at Flexradio Banquet - Hamvention

Mike VE3CKO

I am putting on my speculation hat for a moment. I just read the email from FlexRadio announcing "FlexRadio Banquet - Our Amazing Speakers" and that Rob Sherwood is one of the speakers. As of now I am unable to attend.

What has peaked my interest is what Flexradio says Rob will be discussing:

"Rob will discuss the ARRL's CSI program which includes several off-air screen captures demonstrating excessively wide CW and SSB signals. Also included are a couple of examples of how effective predistortion can be to reduce SSB splatter."   

To me, having Rob Sherwood discuss predistortion is very telling. The Flex community has been desperately waiting for this feature in the 6xxx series, especially now that competitors besides Apache Labs have this feature.

Why would Flexradio invite all kinds of criticism regarding the lack of predistortion in current SmartSDR, unless there is plan. Perhaps some kind of announcement at Hamvention to coincide with and be highlighted by Rob Sherwood and what will be an excellent presentation of a topic he has advocated so much for.

My hope is a new SmartSDR release or at least an announcement of one forthcoming that includes predistortion and that it would be compatible with current FlexRadio products. This will certainly spark new sales and also bring back some who have predistortion at their top feature as their radio of choice.

Russ Ravella

Yup, that would be great. Steve said he had a prototype up and running quite some time ago (two yearsish?) during a Q&A following a presentation at one of the "Virtual Ham Expo"s. And he described "the correct approach" to doing it as well so he'd clearly given it some thought. Fingers crossed.

Russ KR6W

fpmacko

what are the chances if this being compatible with the existing 64/6600 design? I just ordered a 6600 and would be dissapointed if I missed the boat on this one by only a few weeks.

Frank / WA3NHK

Russ Ravella

Hi Frank,

Well to me, going from "announcing adaptive pre distortion " to "announcing a new line of radios with adaptive pre distortion" is a pretty big leap. It would be neat if they did start to roll out a new line of radios, perhaps with an 8 (or more) slice 6700 replacement, from my point of view anyway. But I think the idea here is they might announce the capability in a new version of radio F/W which would presumably run on all the 6xxx models.

The thing is, as I recall Steve specifically stated the right place to sample the output is from the amplifier, if you have one, not the radio's output. Makes sense … And of course the PGXL already has APD outputs built in. But even if only guessing from their connector type (BNC), I wouldn't guess they're not designed to connect directly to 6XXX radios so you might think there'd be an interface box (sampler ?) involved. Perhaps BNC from the amp in, USB out to the radio ? Then the new algorithm would sort things out in the radio. And there might be a "radio only" setting for folks without amps where the radio's output is used ?

All of this is total wild a** speculation of course. I know nothing.

73 Russ KR6W

Trucker

The 6000 Series radios already have the necessary connections inside the radio for Adaptive Pre-Destortion. All that is needed is to make changes to the firmware. ( and SmartSDR) Not sure what type of feedback connection from an amplifier they will need with an amplifier.

James

WD5GWY

Mike VE3CKO

Let's assume if this is really happening, there are two methods to connect from an ADP coupler (PGXL) to the radio:

1. There is some kind of existing termination for that connection point inside the radio and for those of us who don't have a problem opening up the case and adding an appropriate connector or necessary interface board. FlexRadio could also have to offer this mod as an optional bench service too.
2. I thought I heard something way back about utilizing one of the RX inputs for Adaptive Predistortion input.

The 6700 has two RX inputs and I'd hate to loose one as for me the receive antennas will take priority over adaptive predistortion. I suppose I could rig up a simple antenna relay switch between various receive only antennas.

It would also be interesting to see FlexRadios approach the GUI for ADP. While speculating we can also hope for the recently discussed Phase Cancellation in Diversity Receiption for Dual SCU Radios. One can only hope right.

Russ Ravella

I agree about not wanting to loose both or even one of the 6700 RX inputs for this. The receive antenna connection would clearly be the higher priority for me as well. And I also agree about hoping for a full implementation of diversity reception. I've never used Power SDR but from what I understand, they already had it and just didn't complete the job of bringing it forward into SSDR. 10 years on I wish they'd do that now.

And while we're at it, if they also revamped their noise mitigation features to modern standards and fixed user defined waveforms, they'd have all the major boxes checked on my wishlist. As the song says, "I can dream can't I ?"

73 Russ KR6W

fpmacko

I concur re using the PGXL APD output. It's an obvious part of the solution. And one would hope that if you're running a 6000 series radio barefoot then the process can be implemented totally in firmware provided there are sufficient DSP resources available.

For the PGXL implementations I think it quite likely that they will repurpose the ALC input on the radios and keep the feedback totally analog. If they don't then the only way I can see to implement APD with a PGXL would be to develop what we in the avionics world call a "happy box" that would ingest the amp's APD output and digitize it for the radio using either USB or the I2C pins on the accessory port.

73….Frank / WA3NHK

Russ Ravella

Hi Frank,

Yeah, I was thinking along the lines of the latter - some kind of an interface box. To me, Mike's comment about not sacrificing an RX port applies here too. There are going to be folks who use their ALC inputs and won't want to sacrifice it either. Anyway, I hope we get to find out !

73 Russ KR6W

fpmacko

Hi Russ.

Yeah, me too. I wish they were streaming the talks.

73….Frank / WA3NHK