[Elecraft] K2 & PSK-31

[Dave Gingrich K9DC]

On Sunday, Jan 19, 2003, at 13:42 America/Indianapolis, Rod N0RC wrote:

>
> Why? It seems to work just fine. Like I said I'm getting good on
> air results. KSB2 manual says 2:1 compression is OK to use.

The KSB2 Manual was written before the dedicated RTTY settings were 
available in the firmware.  Leaving the compression at 2 is a 
compromise for those that want to run voice with some compression, but 
also use PSK.  Remember, PSK is *simulated* by running a steady state, 
very clean audio signal into a SSB transmitter. Anything that detracts 
from the purity, i.e. adds distortion is a bad thing.  Included in that 
is compression and ALC.

Having ALC bars show up is a worst case scenario for PSK. If you can 
get the appropriate power out with no ALC bars, your signal will be 
cleaner (and more likely to stay legal)

> So it stand to reason that if 1-3 bars is good for voice, it
> should work just fine for PSK-31.

Not true.  Voice is a signal that varies widely in amplitude. 
Compression helps to narrow the spread between the peaks.  With PSK you 
start out with a steady state signal that should not vary at all in 
amplitude, therefore if you are into compression, including ALC, all it 
can do is add distortion. If you limit the ALC to 1-2 bars, then things 
will still be reasonably narrow. But in this case, less is better.

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Dave Gingrich, K9DC
Indianapolis, Indiana USA
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