[Lowfer] New CMSK Program ... WE2XGR/2 in CMSK mode

[Bill de Carle]

At 07:53 AM 8/5/2010, Jay, W1VD wrote:
>John W1TAG and I have been testing a 'pre beta' version of CMSK - 
>a  program developed jointly by
>ZL2AFP and ZL1BPU/ZL1EE. The beta version has now been released and 
>a description and download is
>available at:
>
>http://www.qsl.net/z/zl1bpu/CMSK/cmsk.htm
>
>This program was developed specifically for use at LF and MF, runs 
>MSK using a varicode (very
>similar to that used by PSK31), and  uses Forward Error Correction 
>(FEC). Initial tests have shown
>it to be very robust in the presence of static and fading. It's well 
>known that frequency shift
>keying work best in the presence of static - amplitude modes, like 
>PSK, do not compare favorably.
>Apparently the military realized this years ago as virtually all of 
>their VLF, LF and MF
>transmissions are frequency shift keying. John and I have confirmed 
>this with our tests on LF and
>MF.

There is more to the story and one shouldn't assume MSK is the 
ultimately superior mode in every case.
While the bit-error rates of PSK and MSK are comparable when signals 
are relatively strong, in low static
winter conditions when we are trying to copy extremely weak lowfer 
signals in a more white-noise-like
environment, PSK will increasingly out-perform MSK as the SNR 
decreases.  I would think at VLF the much
smaller bandwidth of MSK for a given message rate would be the 
overriding consideration.

Bill VE2IQ