[hpsdr] predistortion

[FRANCIS CARCIA]

Hi all,
I found AC2IQ on QRZ and had a couple emails with him about his predistortion steup. I hear through the grape vine that he puts out a clean signal. He runs an analog system.
I have a thought for you smart software guys. I just build a nice high power directional coupler in a pomona box with a hunk of RG393 set up as a Faraday shielded coupler. I added a second current transformer to be routed through an attenuator back the the Hermes RX during TX to monitor my signal real time in duplex mode.
This is a great tool for doing IMD testing across the spectrum and saves a ton of time rather than playing with the spectrum analyzer.
Now my thought is since the Hermes RX is monitoring the TX signal, why not use this real time data to feed the predistortion logic hopefully stuffed in the hermes FPGA?? (Systems pukes are such dreamers, usually saved by software pukes.)
The coupler has two .87 inch type 61 cores. One has 50 turns of #28 wirewrap wire and the monitor core has 60 turns. I think I also have about 50 db of atteuation in the monitor path to handle 1500 watts. I wanted to keep the two functions isolated in case I add log amps to the power power meter core. 
Frank WA1GFZ
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