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<DIV>Phillips sells a + 50 dBm , low noise push pull module with extremely low
S12.</DIV>
<DIV>Take a look at their web site.</DIV>
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<DIV>73 de Ulrich N1UL </DIV>
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<DIV>In a message dated 26.07.2006 20:25:18 Westeuropäische Normalzeit,
ray.anderson@xilinx.com writes:</DIV>
<BLOCKQUOTE
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High Performance Software Defined Radio Discussion List *****<BR><BR><BR><BR>
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<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt"><o:p> </o:p></SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt"><o:p> </o:p></SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt">>> Can anyone comment on what
attributes the Makhinson (N6NWP) circuit<o:p></o:p></SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt">>> (which is essentially a pair of Norton amps
in push-pull) brings to the<o:p></o:p></SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt">>> table that would make it preferable over the
Norton amp in this<o:p></o:p></SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt">>> application.<o:p></o:p></SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt"><o:p> </o:p></SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt">>The main advantage of a push-pull amplifier is
that you'll get vastly improved <o:p></o:p></SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt">>second-order inter-mod. performance. The
third-orders will improve by about <o:p></o:p></SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt">>3dB as well.<o:p></o:p></SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt"><o:p> </o:p></SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt">>I have to be a little cautious about what I due to
professional confidences. <o:p></o:p></SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt"><o:p> </o:p></SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt">>It's certainly possible to get around +50dBm IPI3
from a push-pull Norton <o:p></o:p></SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt">>amplifier, and the BFG591 which has been
mentioned, is capable of approaching <o:p></o:p></SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt">>this in the right circuit. There are better
devices... One of the problems <o:p></o:p></SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt">>with the 'traditional' Norton amplifier is that
the load line for the active <o:p></o:p></SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt">>devices doesn't coincide with the conditions for a
50ohm match at the sort of <o:p></o:p></SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt">>currents and voltages necessary for the highest IM
performance. There's also <o:p></o:p></SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt">>the problem that the transistor bias current flows
through the feedback <o:p></o:p></SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt">>transformer, which, of course, causes
magnetisation of the core, and limits <o:p></o:p></SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt">>the dynamic range. That usually means that the
ferrites specified in a <o:p></o:p></SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt">>'traditional' Norton amp. have to be larger than
would be necessary from just <o:p></o:p></SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt">>a signal handling viewpoint.
<o:p></o:p></SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt"><o:p> </o:p></SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt">>There are ways around both of these problems, but
I can't discuss them <o:p></o:p></SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt">>further...<o:p></o:p></SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt"><o:p> </o:p></SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt">>Incidentally, measuring +50dBm plus IPI3 is not a
trivial matter...<o:p></o:p></SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt"><o:p> </o:p></SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt">>The noise figure required of a receiver is
ultimately limited by the noise <o:p></o:p></SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt">>which comes down the antenna cable. At HF and VHF
this is a well known <o:p></o:p></SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt">>quantity, and there are graphs in most of the
standard text books from which <o:p></o:p></SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt">>it can be calculated. If you work on the basis
that the receiver system will <o:p></o:p></SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt">>not degrade the available S/N by (say) 1dB, then
receiver noise figures of <o:p></o:p></SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt">>10dB at 10m and 6dB on 6m are more than adequate.
I know that there's a <o:p></o:p></SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt">>market for (allegedly) 0.3dB NF pre-amps for 6m,
but any system performance <o:p></o:p></SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt">>improvement they bring is more likely to be
psychological than real...<o:p></o:p></SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt"><o:p> </o:p></SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt">>Vy 73<o:p></o:p></SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt"><o:p> </o:p></SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt">>Chris<o:p></o:p></SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt">>GW4DGU<o:p></o:p></SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt"><o:p> </o:p></SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt">-- <o:p></o:p></SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt"><o:p> </o:p></SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" color=black size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: black">Chris-<o:p></o:p></SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" color=black size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: black"><o:p> </o:p></SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" color=black size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: black">Thanks for your insightful comments
regarding Norton amps and noise performance. I fully understand your inability
to get into specifics due to proprietary
considerations.<o:p></o:p></SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" color=black size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: black"><o:p> </o:p></SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" color=black size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: black">It is looking like we may be able to
obtain very good performance on the HF bands without the need for a preamp,
however on 6 meters some noise figure improvement may be beneficial to the
system performance. I may look into the feasibility of a switchable preamp so
that the circuit may be used when necessary, but may removed when
not.<o:p></o:p></SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" color=black size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: black"><o:p> </o:p></SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" color=black size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: black"><o:p> </o:p></SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" color=black size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: black">73 Ray
WB6TPU<o:p></o:p></SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt"><o:p> </o:p></SPAN></FONT></P></DIV><BR><BR>_______________________________________________<BR>HPSDR
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