[RTTY] AFSK Splatter

[Andy swiffin]

> problem.
> 
> Furthermore, depending on where the clipping happens, the ALC could
> be showing no reading and yet the transmitted signal can still be
> splattering all over.
> 


There is one area where clipping occurs which caught me out, and I
didn't spot it as a problem until I started using PSK.

This is in the audio stage _before_ the mic gain.  I had been using
rtty afsk for a while with no bad reports (everyone too kind?) but when
I started using PSK I was getting bad IMD reports.  The rig (TS830) was
not showing any ALC and even when I reduced power using the Mic gain IMD
was still bad.  

The answer was very simply the audio level going into the mic socket,
clipping was occuring in audio stages before the Mic gain control.   I
attenuate the input now and have the Mic gain turned up higher than I
normally do on SSB and suddenly the PSK IMD dropped right down.  

Anyone with any text showing how to set up AFSK from a PC would do well
to labour the point  - tell people to use the minimum level into the Mic
socket and increase the Mic gain to compensate.  I find with my ancient
PC that I get the best sound out of my sound card with the PC levels set
quite high and I use an attenuator between the PC and the TS830 to
reduce the level.

Cheers
Andy 
gm8oeg