<div dir="ltr">Helmut<div><br></div><div>I wonder what part of the Chris's message implied that he was "obviously" not satisfied with the pure signal performance? :)<div><div><br></div><div>At the bottom of this page <a href="http://pavel-demin.github.io/red-pitaya-notes/sdr-transceiver-hpsdr/">http://pavel-demin.github.io/red-pitaya-notes/sdr-transceiver-hpsdr/</a> there is a screenshot of what looks like an excellent improvement after applying the PS.</div><div><br></div><div>Also could you point to the discussion about losses in DDC/DUC chain in red pitaya?.. </div><div><br></div><div>73! Vasiliy</div><div><br></div></div></div></div><div class="gmail_extra"><br><div class="gmail_quote">On Tue, Jun 28, 2016 at 1:04 PM, Helmut <span dir="ltr"><<a href="mailto:dc6ny@gmx.de" target="_blank">dc6ny@gmx.de</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><span class="">***** High Performance Software Defined Radio Discussion List *****<br>
<br>
</span>Hi Chris,<br>
<br>
Obviously you are not completely satisfied with Red Pitaya, the modified<br>
PowerSDR and PS. That’s no big surprise, but it’s a much better approach for<br>
linearization than that (strange) ‘hardware solution’.<br>
The efficiency of predistortion depends on the measurement precision of the<br>
actual TX signal and the reference TX signal or in other words the<br>
measurement dynamic range. Otherwise you can‘t precisely take correction.<br>
‘Dynamic losses’ due to the necessary up/down conversion reduce the<br>
efficiency of predistortion dramatically. High losses in the Red Pitaya<br>
DDC/DUC paths limit the great performance of Warren’s PS algorithm. As the<br>
losses are 4 times more than in Hermes, I guess the improvement of IMDR<br>
results only on a limited correction in the upper part of the amp transfer<br>
characteristic. This also explains your observation of critical feedback<br>
levels. An improvement/correction at low levels seems very difficult, so<br>
you should at least operate your amp with a high quiescent current.<br>
<br>
73, Helmut, DC6NY<br>
<br>
-----Ursprüngliche Nachricht-----<br>
Von: Hpsdr [mailto:<a href="mailto:hpsdr-bounces@lists.openhpsdr.org">hpsdr-bounces@lists.openhpsdr.org</a>] Im Auftrag von Chris<br>
Wilson<br>
Gesendet: Dienstag, 28. Juni 2016 15:49<br>
An: 'OpenHPSDR'<br>
Betreff: [hpsdr] Hardware pre distortion?<br>
<div class="HOEnZb"><div class="h5"><br>
***** High Performance Software Defined Radio Discussion List *****<br>
<br>
28 June 2016<br>
<br>
<br>
I hope this is a suitable question for this group? I am messing with a<br>
Red Pitaya experimental board and a special version of OpenHPSDR<br>
software that allows pre distortion using "PureSignal" and it works<br>
very well once the feedback levels are set correctly. But i am now<br>
wondering what the state of play is with hardware pre distortion that<br>
is software independent? Anyone got any info on this please? Thanks.<br>
<br>
<br>
<br>
--<br>
<br>
<br>
Best regards,<br>
Chris mailto:<a href="mailto:chris@chriswilson.tv">chris@chriswilson.tv</a><br>
<br>
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