First all digital radio transmitter

Richard McClelland, AA5S

A link to this article was posted locally here in Fort Collins:  http://www.cambridgeconsultants.com/media/press-releases/first-all-digital-radio-transmitter

"Technology innovation firm Cambridge Consultants has successfully
completed initial trials of the world’s first fully digital radio transmitter – a turning point in wireless design..."

N7AIG

I must be missing something... How do you achieve useful power from computer bits? Don't you need to go to the analog domain and apply amplification?

73 de Dave, N7AIG

Ken - NM9P

Probably with a HUGE digital voltage switch. Probably square waves, or PW modulation, etc. but I can't imagine SSB with an all digital rig. Unless some of the new Class E amps are involved...

Richard McClelland, AA5S

Maybe I should have posted this on 4/1 instead?   

Jay Nation

Linked site is PR/Marketing mostly,There #1 product. Mostly of an infomercial. for investors, they're not marketing a product, just marketing their PR. Seems geared for data over digital wireless or DV or Netflix throughout the home. They sort of skipped past detail in favor of Buzzwords and self praise.
73, Jay - NO5J 

N7AIG

well... I feel relieved to know that I didn't miss some technology revolution... For a moment I thought I had been living in my cave too long...

73 de Dave, N7AIG

N7AIG

Speaking of amplifiers... it just occurred to me... how will internally applied Adaptive PreDistortion help if you run an outboard linear amplifier? Never thought beyond the basic concept before now...

(PS: this is a serious question. From what I have seen lately on Amp specs, they are typically running -35 dBc for IMD. Seems barely acceptable, especially with high output power.)

73 de Dave, N7AIG

Jay Nation

Nice case design though, or do I buy my own sardines? Altoids would smell better in the shack. 60 gHz? Shortrange broadband NSA/CIA surveillance? Maybe they've been in the cave too long. 

73, Jay - NO5J

Jay Nation

Sample the output of the amp through a hefty attenuator and feed it back to the RX loop jacks. Or maybe an add on accessory board. How do Anan and HPSDR do it? It might explain the comments I've seen about the Anan's getting warm on transmit.
I dunno.
Found this, https://www.wavenode.com/PureSignal.pdf
73, Jay - NO5J

N7AIG

The film clips I have seen about APD on the Anan's shows them sampling only the output of the rig itself. I have seen the comments about them getting a bit warm, but that has nothing to do with APD. I think it is a slight under-design of the rig that accounts for the warming.

It is one thing to correct the rig for its IMD behavior with APD. But to accomplish that *and* correct the output of a follower linear amplifier might seem to be working at cross purposes. Corrections applied to the driver might exacerbate IMD in the follower amplifier. Seems like you need two stages of APD.

OTOH, the amplifier probably can't make things any cleaner than they are coming in, so by reducing crud on the input you might still be accomplishing a lot.

How do the telecom folks deal with this? Isn't that where this technology was initially developed?

73 de Dave, N7AIG

Peter Bentley

A very interesting article.

Perhaps Flexradio should commission them to design the next generation product.

Jay Nation

Dave 

Reply being created and edited (removing typos and errors)
Even though, by the time I get it posted, you may have already figured out the answer for yourself, I'll post it anyway, It might help, others who get stuck along the way.
It's pretty simple, to understand without the (typos and errors).
I just need to edit up an explanation of ... (editing)  
Answer to be forthcoming
Hint: Your reply contains the answer.
God I'm awful! 

73, Jay - NO5J

Jay Nation

Dave 
After several attempts to write up something. I've come to the realization that the
article I linked explains it better than I can. Without knowing how Flexradio is going to implement PureSignal I can only guess how it might work. It works because it samples the output after the amp, be it the PA in the exciter, or the amplifier.
Its not just reducing the crud going into the amp it's correcting for the crud coming out of the amp. It's not cross-purpose, it's the whole purpose. It tries to create and inject negative IMD for the IMD it's sampling. It doesn't filter IMD it inverts it. The input of the amp isn't seeing less IMD. It's getting UN-IMD and then adding its own IMD so it cancels out.

Best I can do with words on a page, there are videos out there that do a much better job. With a video you can see and hear the result. 

73, Jay - NO5J

N7AIG

Hi Jay,

I have given a brief interval of thought to the problem. I do see that as long as you can linearize small behavior departures this would be possible in combination. But the reality is that we are trying to overcome nonlinear behavior. So perhaps the nonlinearities are truly small enough to allow this approach successfully. Has anyone actually tried this with an outboard amplifier on an Anan box? Just curious.

73 de Dave, N7AIG