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<DIV><FONT face=Arial size=2>Hi Frank, </FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Elecraft use T50 cores in the K2 100w PA without
any problems. In terms of the DDS we are using 18 bits for the sine/cosine
calculations and a high quality 14 bit DAC. </FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>On receiver the DDS (actually a CORDIC NCO)
spurs are >100dB down and whilst on transmit the DAC will degrade this
somewhat even with </FONT><FONT face=Arial size=2> just a 55MHz LPF on the
output of the DAC we are well within the FCC requirements for a
transmitter.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>I don't think there is any cause for concern. In
fact given that there are no analog mixers involved, and we are generating the
RF output directly at the input to the DAC, Penelope could well turn out
to be one of the cleanest transmitters around. </FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>73's Phil...VK6APH </FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
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<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B>
<A title=carcia@sbcglobal.net href="mailto:carcia@sbcglobal.net">FRANCIS
CARCIA</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A title=hpsdr@lists.hpsdr.org
href="mailto:hpsdr@lists.hpsdr.org">hpsdr@lists.hpsdr.org</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Friday, July 27, 2007 12:18
AM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> [hpsdr] Alex</DIV>
<DIV><BR></DIV>***** High Performance Software Defined Radio Discussion List
*****<BR><BR>
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<DIV>I would avoid using T50 cores at 100 watts. Might get away with stacking
2 or 3 cores.</DIV>
<DIV>Red for low end and yellow 40 meters and above</DIV>
<DIV>T68 work well up to around 200W. Also allows larger wire to keep the
resistance low.</DIV>
<DIV>Check RF current rating of caps might need to parallel multiple units to
keep them cool.</DIV>
<DIV>Stay away from XR7 dielectric caps. </DIV>
<DIV>Relays use the ones about the size as a SRA1 mixer can. Then can take the
voltage. </DIV>
<DIV>Add at least a gas tube for static protection. I would think some sort of
a clipper needs to be ahead of an expensive A/D. Biased Transorbs
isolated by low C fast diodes at least.</DIV>
<DIV>I'm a bit worried about a D/A making a clean signal. We know what a D/A
in a DDS does, how is this different? frank wa1gfz</DIV>
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