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<H1><IMG src="http://www.qsl.net/zl1bpu/CMSK/VK2DDIcmsk.jpg"></H1>
<H1>New narrow-band mode for LF/MF released</H1>
<P><FONT face=Tahoma><STRONG>Con Wassilieff ZL2AFP</STRONG> has recently
released a new narrow-band digital mode, CMSK, designed specifically for the LF
and MF ham radio bands (2200, 600 and 160m). </FONT></P>
<P><FONT face=Tahoma>The mode uses MSK modulation, familiar to LF and MF
listeners as the mode most used by commercial and military transmissions. One
major advantage of MSK is that unlike PSK, it does not require linear
amplification to maintain narrow bandwidth.</FONT></P>
<P><FONT face=Tahoma>The new <STRONG>ZL2AFP CMSK</STRONG> mode can be described
as Correlated, Convolved Minimum Shift Keying, and uses a full-time NASA
standard convolutional coder with a generous interleaver to provide impressive
QRN resistance.</FONT></P>
<P><FONT face=Tahoma>Synchronism is assured, even on very weak signals, by a
transmitted PN-sequence frame marker and cross-correlator at the
receiver.</FONT></P>
<P><FONT face=Tahoma>Four modes have been provided, from 125 baud (<200Hz
bandwidth, 60 WPM) down to 7.8 baud (12.5Hz bandwidth, 4WPM). The narrowest and
slowest mode is intended for beacon applications, and can be received 100% at
-21dB S/N in 3kHz bandwidth. The default mode, CMSK63, has been reliably copied
across the Tasman, at a range of 2200km on 600m from a transmission well under
1W EIRP.</FONT></P>
<P><FONT face=Tahoma>Software for this new mode is now available
from<BR></FONT><A href="http://www.qsl.net/zl1bpu/CMSK/cmsk.htm"
target=_blank><FONT face=Tahoma>www.qsl.net/zl1bpu/CMSK/cmsk.htm</FONT></A><FONT
face=Tahoma>, where a description of the design is also given.</FONT></P>
<P><FONT face=Tahoma> </FONT></P>
<P><STRONG><EM><FONT face=Tahoma>Murray Greenman
ZL1BPU/ZL1EE</FONT></EM></STRONG><BR></P></BODY></HTML>